Patent Publication Number: US-2018035624-A1

Title: Plant cultivation device and plant cultivation system

Description:
TECHNICAL FIELD 
     The present invention relates to a plant cultivation device for continuously cultivating plants such as field crops. The present invention also relates to a plant cultivation system formed by combining a plant cultivation device and an accompanying device. 
     BACKGROUND ART 
     There has been known a plant cultivation device where field crops are continuously cultivated inside a building. The plant cultivation device is used for a cultivation mode usually referred to as a crop factory. That is, the plant cultivation device is a device where crops are grown by exposing crops to a proper amount of lighting by using an artificial illumination and by keeping the inside of the building or the inside of a room at a temperature and a humidity suitable for growing crops. 
     With the use of such a plant cultivation device, crops can be produced in an environment where amount of lighting, temperature, moisture, concentration of a fertilizer and the like are properly controlled. Accordingly, with the use of the plant cultivation device, a period necessary for harvesting can be shortened compared to an open field culture. 
     Among all plant cultivation devices, many plant cultivation devices are used for growing crops by hydroponic culture. Hydroponic culture is clean compared to open culture. Further, in hydroponic culture, crops are cultivated indoors and hence, it is possible to prevent crops from being infested with harmful insects and hence, crops can be cultivated without using agricultural chemicals. Accordingly, the plant cultivation device is suitable for cultivating vegetables, such as lettuce, which can be eaten without requiring peeling of a skin. 
     In plant cultivation devices disclosed in Patent Documents 1, 2, a conveyor device which advances at an extremely low speed is used as a main unit. A cultivation tray in which seedlings are planted is placed on a start end portion of the conveyor device, and the cultivation tray is moved to a growing area. In the growing area, lighting is ensured by artificial illumination. The above-mentioned cultivation tray is placed on the conveyor device and the cultivation tray is slowly advanced in the growing area. 
     When the cultivation tray reaches a terminal end of the conveyor device, seedlings are grown to a size enough to be harvested. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     Patent Document 1: JP H02-60529 A 
     Patent Document 2: JP 2001-78577 A 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     In the plant cultivation device of prior art, the whole configuration including a building or a room formed by partitioning the inside of the building forms one plant cultivation device and hence, construction work, repair, partial improvement or remodeling work becomes a large-scale operation. 
     In the plant cultivation device of the prior art, the whole environment in the building or in the room is maintained at a temperature and a humidity suitable for growing a plant to be cultivated. 
     Accordingly, a large amount of heat or cold is necessary for maintaining the environment and hence, the plant cultivation device of the prior art has a drawback that energy cost is high. 
     Further, as described above, in the plant cultivation device of the prior art, the environment in the whole building or the whole room is maintained at a temperature and a humidity suitable for growing a plant to be cultivated and hence, it is difficult to cultivate plants having different growing conditions in mixture. 
     For example, it is difficult to simultaneously cultivate crops which prefer high temperature and high humidity and crops which prefer a cool environment in the same building or in the same room. 
     In the plant cultivation device of the prior art, the invasion of harmful insects such as a cabbage butterfly, an aphid, or a locust into a building or a room must be strictly prohibited and hence, a strict harmful insect invasion preventing unit is mounted at an entrance and an exit, a ventilation window and the like of the building or the like. When a harmful insect invades the building or the room by a chance, the extermination of the harmful insect is extremely difficult. That is, in the plant cultivation device, agricultural chemicals are not used in principle. Accordingly, there may be a case where the cultivation of crops must be suspended for several days. 
     The present invention has been made by focusing on the above-mentioned drawbacks that the plant cultivation device of the prior art has, and it is an object of the present invention to provide a plant cultivation device where installation work, repair, partial improvement or remodeling work can be performed easily, energy cost can be reduced, and countermeasures for exterminating harmful insects or the like can be also easily taken. 
     Solution to Problem 
     According to an aspect to overcome the above-mentioned drawbacks, there is provided a plant cultivation device including: a plurality of cultivation trays having seedlings or seeds of a plant planted thereon; an illumination unit irradiating the plant with light; a conveyance unit sequentially moving the cultivation trays toward a downstream side from an upstream side with simultaneous allowance of growth of the plant on the cultivation trays; and a plurality of seedling growing units, each of the seedling growing units including a case with both ends thereof opened, the case being capable of covering a peripheral surface of the seedling growing unit, wherein the cases of the plurality of seedling growing units are connected to each other to form a continuous cylindrical space, and wherein the cultivation trays are placed in the continuous cylindrical space formed by the cases, the cultivation trays being moved toward the downstream side across the cases by the conveyance unit. 
     The plant cultivation device according to this aspect includes the plurality of seedling growing units, and the cylindrical space which becomes a cultivation space is formed by connecting the seedling growing units. The cultivation trays are moved toward the downstream side by the conveyance unit in a state where the cultivation tray strides over the case. 
     The respective seedling growing units can be manufactured at a manufacturing factory. 
     In the present invention, it is assumed that the respective seedling growing units are manufactured at a manufacturing factory. The seedling growing units manufactured in the manufacturing factory are carried in an installation site and are connected to each other thus completing the plant cultivation device. 
     According to the present invention, operations in the installation site can be largely reduced. Accordingly, an installation work of the plant cultivation device according to the present invention can be performed easily. 
     By performing a repair of the plant cultivation device by removing the seedling growing unit, it is possible to prevent a repair work from becoming a large-scale operation. 
     An entire length of the plant cultivation device or a growing period of a plant can be changed by changing the number of seedling growing units to be connected to each other. 
     It is sufficient to perform environmental adjustment only in the continuous cylindrical space. Accordingly, a space which requires environmental adjustment can be reduced and hence, energy necessary for environmental adjustment can be reduced. 
     The plant cultivation device according to the present invention can also easily exterminate harmful insects when the harmful insects invade the plant cultivation device. That is, according to the present invention, the space which requires extermination of insects becomes small and, further, imagoes, larvae, and eggs of harmful insects minimally hide themselves in the space and hence, the harmful insects can be easily exterminated even when the harmful insects invade the plant cultivation device. 
     It is desirable that the illumination unit be disposed inside the case. 
     In addition to the above-mentioned configuration, it is desirable that the continuous cylindrical space be formed by three or more seedling growing units, and the seedling growing unit disposed in an intermediate portion be individually detachably mounted. 
     According to this aspect, maintenance of the plant cultivation device is facilitated. 
     It is desirable that the cases which are disposed adjacently to each other be arranged in a state where end portions of the cases face each other, and the cases disposed adjacently to each other be connected to each other with a connecting member interposed between the end portions of the cases. 
     According to this aspect, the case disposed at an intermediate portion can be easily removed. 
     It is desirable that the cases of the seedling growing units be lineally disposed with a distance, a connecting member be disposed between the cases of the adjacent seedling growing units, and sealing property be held between the adjacent cases by the connecting member to form a continuous cylindrical space. 
     According to this aspect, a distance is provided between the cases. Accordingly, the connection of pipes or the like can be performed between the cases. 
     It is desirable that the case of the seedling growing unit include therein: a placing table placing the cultivation tray thereon; and a pressing member pressing the cultivation tray toward the downstream side. 
     The pressing member may be operated by power such as a motor, a pneumatic pressure, or a hydraulic pressure. The pressing member may rely on man power such as power generated when an operator manually rotates the pressing member. 
     A motor or the like which drives the pressing member may be disposed inside the case. A motor or the like which drives the pressing member may be disposed outside the case. 
     It is desirable that the pressing member which presses the cultivation tray toward the downstream side be incorporated inside the case of the seedling growing unit, the pressing members in the plurality of cases be connected to each other by connecting members, and the pressing members in the plurality of cases be driven by a same power source. 
     According to this aspect, the number of power sources for driving the pressing members can be reduced. 
     The configuration may be employed where the pressing member which presses the cultivation tray toward the downstream side, and a part of a moving mechanism which moves the pressing member are incorporated inside the case of the seedling growing unit, and a power transmission member which transmits power between the moving mechanisms incorporated in the cases disposed adjacently to each other is disposed between the cases disposed adjacently to each other. 
     According to this aspect, the number of power sources for driving the pressing members can be reduced. Further, the power transmission member is disposed between the cases disposed adjacently to each other and hence, the power transmission member can be easily mounted or removed. 
     It is recommended that the plant cultivation device includes an open/close member which opens/closes an opening of a continuous cylindrical space on at least one end side. 
     According to this aspect, the cylindrical spaces can be sealed. 
     It is desirable that the open/close member include a sheet-like member and a moving unit which moves the sheet-like member, an opening be formed in the sheet-like member, the cylindrical space be opened by making a position of the opening and the cylindrical space agree with each other, and the cylindrical space be brought into a sealed state by making portions other than the opening agree with the cylindrical space. 
     It is desirable that a part or the whole of an inner surface of the case exhibit a reflectance of 40% or more. 
     Although the reflectance differs depending on a wavelength of light, the reflectance is determined with reference to sunbeam in the aspect. 
     It is desirable that the case include: a ceiling surface bent in an arcuate shape; the cultivation trays therein; and the illumination unit on the ceiling surface, the illumination unit being formed of a plurality of light emitting elements, and density of arrangement of the light emitting elements in the vicinity of a peak of the ceiling surface be lower than in outskirt regions of the ceiling surface. 
     It is desirable that the illumination unit flicker at a fine time interval. 
     To compare a growing state when a plant is irradiated with illumination which continuously emits light and a growing state when a plant is irradiated with light which flickers at a fine time interval which cannot be distinguished by naked eyes, there is no large difference between both growing states. Accordingly, in this aspect, the illumination unit which flickers at a fine time interval is adopted. According to this aspect, power consumption of the illumination unit can be reduced. 
     It is desirable that the plant cultivation device include a water cooling unit which cools an outer peripheral surface of the case by water. 
     For example, when the illumination unit is incorporated inside the case, a temperature inside the cylindrical space is excessively elevated due to heat generated by illumination. According to this aspect, the plant cultivation device includes the water cooling unit which cools the outer peripheral surface of the case by water and hence, the excessive elevation of a temperature in the cylindrical space can be suppressed. 
     Since the illumination is mounted on a ceiling portion of the case in many examples and hence, it is desirable to cool a roof portion of the case by water. 
     When the plant cultivation device adopts the configuration where the outer peripheral surface of the case is cooled by water, it is desirable that the outer peripheral surface of the case be covered by a member having a moisture retaining property so as to always bring the outer peripheral surface of the case in a wet state. 
     It is desirable that at least any one of the following constitutional elements be disposed between the cases.
     (1) connecting unit and/or merging unit of supply passages of culture solution   (2) branching unit for branching branch pipe from main pipe through which culture solution is supplied   (3) connecting unit and/or merging unit of discharge passages of culture solution   (4) connecting unit and/or merging unit of electric wiring of illumination   (5) branching units leading to respective illuminations from main line of electric wiring of illumination   (6) connecting unit and/or merging unit of air conditioning ducts   (7) branching unit of air conditioning duct   (8) connecting unit and/or merging unit of carbon dioxide pipes   (9) branching unit of carbon dioxide pipe   (10) valve   (11) distributer   (12) fuse   

     It is desirable that the plant cultivation device include a holding member for holding the plurality of cases, the holding member include a bottom support portion which supports a bottom of the case, the bottom of the case be supported by the bottom support portion, and the case be configured to move in a direction which intersects with an axial direction of the cylindrical space by being slid on the bottom support portion. 
     According to this aspect, the case is supported by the bottom support portion. Further, the case can be moved in the direction which intersects with the axial direction of the cylindrical space by being slid on the bottom support portion. Accordingly, a case exchanging operation and a case installing operation can be performed easily. That is, according to this aspect, the case exchanging operation and the case installing operation can be performed by laterally sliding the case. 
     According to an aspect of a plant cultivation system, the plant cultivation devices respectively having the above-mentioned configuration are installed in plural stages and/or in plural rows. 
     According to this aspect, it is possible to effectively make use of a space. 
     According to another aspect of a plant cultivation system which is an improvement of the above-mentioned system, there is provided a plant cultivation system having a plurality of the plant cultivation devices having the above-mentioned configuration, the plant cultivation system including: the plant cultivation device for young seedlings that has a low height of the cylindrical space; and the plant cultivation device for grown seedlings that has a higher height of the cylindrical space than the plant cultivation device for young seedlings. 
     According to this aspect, it is possible to use the plant cultivation device having a proper height in conformity with a growth of seedling. Accordingly, it is possible to effectively make use of the space. 
     According to another aspect of a plant cultivation system which is an improvement of the above-mentioned system, there is provided a plant cultivation system which includes a plurality of plant cultivation devices having different structures and/or different environments inside the cylindrical space. 
     According to another aspect of a plant cultivation system which is an improvement of the above-mentioned system, there is provided a plant cultivation system having a plurality of the plant cultivation devices having: different structures, and/or different environments of the cylindrical spaces; and a tray exchange device transferring the cultivation tray from one of the plant cultivation devices to another of the plant cultivation devices. 
     According to this aspect, it is possible to easily perform an operation of transferring the cultivation tray from one plant cultivation device to another plant cultivation device. 
     According to another aspect of a plant cultivation system which is an improvement of the above-mentioned system, there is provided a plant cultivation system which includes a group of plant cultivation devices where plant cultivation devices are disposed in plural stages and/or in plural rows, and a unit conveyance device disposed in the vicinity of the group of plant cultivation devices, and the unit conveyance device includes: a fork portion which is insertable into a bottom side of a seedling growing unit and holds the seedling growing unit from below; a lifting and lowering unit capable of lifting and lowering the fork portion; and a traveling unit capable of moving the fork portion along the row of the seedling growing units. 
     According to this aspect, an installing operation and an exchanging operation of seedling growing units can be easily performed. 
     According to another aspect of a plant cultivation system which is an improvement of the above-mentioned system, there is provided a plant cultivation system which includes a group of plant cultivation devices where plant cultivation devices are disposed in plural stages and/or in plural rows, and a conveyor device additionally disposed at least above or below the group of plant cultivation devices. 
     It is desirable that the conveyor device be used for conveying empty cultivation trays or cultivation trays on which plants are grown. 
     According to another aspect of a plant cultivation system which is an improvement of the above-mentioned system, there is provided a plant cultivation system which includes a group of plant cultivation devices where plant cultivation devices are disposed in plural stages and/or in plural rows, and at least one of the following constitutional elements is disposed above or below the group of plant cultivation devices.
     (1) power supply cable   (2) flow passage for culture solution   (3) carbon dioxide pipe   (4) air conditioning duct   (5) signal lines   

     According to an aspect of a comprehensive plant cultivation system, there is provided a plant cultivation system where a group of plant cultivation devices is formed by disposing plant cultivation devices in plural stages and/or in plural rows, the group of plant cultivation devices includes plant cultivation devices for young seedlings where a height of a cylindrical spaces is low and plant cultivation devices for grown seedlings where a height of a cylindrical space is higher than the height of the cylindrical space in the plant cultivation devices for young seedlings thus providing the plurality of plant cultivation devices which differ from each other in structure and/or an environment in the cylindrical space, the plant cultivation system includes a tray exchange device capable of transferring a cultivation tray from one plant cultivation device to another plant cultivation device, the plant cultivation system includes a unit conveyance device disposed in the vicinity of the group of plant cultivation devices, the unit conveyance device includes: a fork portion which is insertable into a bottom side of a seedling growing unit and holds the seedling growing unit from below; a lifting and lowering unit capable of lifting and lowering the fork portion; and a traveling unit capable of moving the fork portion along the row of the seedling growing units, a conveyor device is additionally disposed at least above or below the group of plant cultivation devices, and at least one of the following constitutional elements is disposed above or below the group of plant cultivation devices.
     (1) power supply cable   (2) flow passage for culture solution   (3) carbon dioxide pipe   (4) air conditioning duct   (5) signal lines   

     It is desirable that air pressure in the cylindrical space be held more than atmospheric pressure. 
     In the above-mentioned respective aspects, it is desirable that the plant cultivation device include an air supply unit moving air in the cylindrical space by supplying air, the air supply unit including a supply air volume adjusting unit changing a supply air volume for respective areas. 
     According to this aspect, wind is generated in the cylindrical space so that an environment close to nature is created and plants can be grown in such an environment. 
     It is desirable that the supply air unit include an air supply passage forming member in the cylindrical space, the air supply passage forming member including a plurality of air supply ports supplying air into the cylindrical space. 
     It is desirable that the plant cultivation device include an air volume adjusting unit that opens or closes the air supply ports, or adjusts opening degree of the air supply ports. 
     It is desirable that the air supply passage forming member include a plurality of blowers therein in series with a distance, and the air supply ports be disposed between an air supply side of the blower on an upstream side and a suction side of the blower on a downstream side. 
     The number of days required for the growing of plants ranges from approximately 10 days to 30 days. Accordingly, an entire length of the cylindrical spaces becomes considerably long and hence, the supply air passage forming member also inevitably becomes considerably long. Accordingly, it is difficult to supply air to a terminal end of the air supply passage forming member with the configuration where air is supplied by disposing the blower only on the end portion of the air supply passage forming member. 
     Accordingly, in this aspect, the configuration is adopted where the plurality of blowers are incorporated in the air supply passage forming member in series at intervals. 
     In the above-mentioned respective aspects, it is desirable that the plant cultivation device include a culture solution supply unit supplying a culture solution to the cultivation trays, the culture solution supply unit including a solution amount adjusting unit adjusting an amount of the culture solution to be supplied to the cultivation trays. 
     It is desirable that the solution amount adjusting unit include an auxiliary pump, the auxiliary pump being attached to each of the plurality of seedling growing units. 
     In the above-mentioned respective aspects, it is desirable that the cultivation tray capable of storing a culture solution therein include: a discharge port discharging a surplus culture solution; and a culture solution supply unit supplying the culture solution to the cultivation tray from a point close to one side of the cultivation tray, and the discharge port of the cultivation tray be disposed at a position close to the side to which the culture solution is supplied. 
     In the above-mentioned respective aspects, it is desirable that the cultivation tray include a culture solution flow passage configured in such a manner that a culture solution is supplied to the cultivation tray from the culture solution supply unit, is circulated inside the cultivation tray, and reaches the discharge port. 
     According to this aspect, a culture solution flows into the cultivation tray and hence, it is possible to prevent the culture solution from stagnating in a particular place. 
     In the above-mentioned respective aspects, it is desirable that the cultivation tray be configured to store a culture solution therein, and the plant cultivation device include a cultivation tray inclining unit that discharges the culture solution by inclining the cultivation tray. 
     The cultivation tray inclining unit is made to function at the time of discharging the cultivation tray from the cylindrical space as in the case of harvesting plants, for example. By inclining the cultivation tray by the cultivation tray inclining unit thus discharging a culture solution, a weight of the cultivation tray is decreased so that the cultivation tray can be easily discharged. Further, it is possible to prevent a culture solution from being spilled on an outside floor or the like. 
     It is desirable that a plant cultivation system have the plant cultivation devices having the above-mentioned configuration, the plant cultivation system including a lifting and lowering device lifting and lowering the cultivation tray thereon. 
     It is desirable that a plant cultivation system having the plant cultivation devices having the above-mentioned configuration are disposed in plural stages, the plant cultivation system including a lifting and lowering device lifting and lowering the cultivation tray thereon, wherein the conveyance unit of the plant cultivation device includes a linearly moving member that linearly moves, the linearly moving member including a tray facing engaging portion, the tray engaging portion engaging with the cultivation tray to convey the cultivation tray, and wherein the lifting and lowering device includes a conveyance unit drive device driving the conveyance unit of the plant cultivation device. 
     It is desirable that the conveyance unit have a conveyance-unit-side engaging portion and the conveyance unit drive device has a drive-side engaging portion engaging with the conveyance-unit-side engaging portion, the conveyance-unit-side engaging portion and the drive-side engaging portion be capable of performing engagement and release of engagement by relative movement of the engaging portions in a vertical direction, and the engagement and the release of the engagement between the conveyance-unit-side engaging portion and the drive-side engaging portion be performed by lifting and lowering the lifting and lowering device. 
     It is desirable that a plant cultivation system be configured such that the plant cultivation devices having the above-mentioned configuration are disposed in plural stages, the plant cultivation system including a lifting and lowering device lifting and lowering the cultivation tray thereon, wherein the cultivation tray is configured to store a culture solution therein, and wherein the plant cultivation device includes a cultivation tray inclining unit that discharges the culture solution by inclining the cultivation tray. 
     It is desirable that the cultivation tray inclining unit include an inclining engaging member engaging with the cultivation tray, and the lifting and the lowering member be elevated with the inclining engaging member engaged with the cultivation tray to incline the cultivation tray. 
     It is desirable that the plant cultivation system include a moving unit that moves the inclining engaging member toward the cultivation tray, wherein the inclining engaging member moves from a position where the inclining engaging member is not engageable with the cultivation tray to a position where the inclining engaging member is engageable with the cultivation tray. 
     Effect of Invention 
     The plant cultivation device and plant cultivation system according to the present invention can easily perform an installation work, repair, partial improvement or remodeling work, can reduce energy cost, and easily take measures to exterminate harmful insects. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view showing an overall view of a plant cultivation device (plant cultivation system) according to an embodiment of the present invention. 
         FIG. 2  is a perspective view showing an overall view of the plant cultivation device (plant cultivation system) where the plant cultivation device (plant cultivation system) shown in  FIG. 1  is expressed in the form of a model. 
         FIG. 3  is a conceptual view of the plant cultivation device (plant cultivation system) shown in  FIG. 2  where the plant cultivation device (plant cultivation system) is divided into zones functionally. 
         FIG. 4  is a perspective view of a portion of a grown seedling frame and a seedling growing unit of the plant cultivation device shown in  FIG. 2 . 
         FIG. 5A  and  FIG. 5B  are perspective views showing the configuration of a unit plant cultivation device, wherein  FIG. 5A  shows a state where connecting members are removed from between seedling growing units, and  FIG. 5B  shows a state where the seedling growing units are connected to each other. 
         FIG. 6  is a perspective view showing the inner structure of the seedling growing unit shown in  FIG. 5A  and  FIG. 5B . 
         FIG. 7  is a perspective view showing the inner structure of the seedling growing unit shown in  FIG. 5A  and  FIG. 5B  in a state where cultivation trays are inserted into the seedling growing unit. 
         FIG. 8  is a partially enlarged perspective view of end portions of the seedling growing units showing the inner structure of the seedling growing units and a relationship between the seedling growing units disposed adjacently to each other. 
         FIG. 9  is a front view showing the inner structure of the seedling growing unit shown in  FIG. 5A  and  FIG. 5B . 
         FIG. 10  is an exploded perspective view of a cultivation tray used in the plant cultivation device shown in  FIG. 2 . 
         FIG. 11A  to  FIG. 11D  are explanatory views showing an operation of moving cultivation trays by a conveyance device incorporated into the seedling growing units shown in  FIG. 4 . 
         FIG. 12  is a perspective view showing a portion of a grown seedling frame of the plant cultivation device (plant cultivation system) shown in  FIG. 2 . 
         FIG. 13  is a perspective view of an opening and closing unit adopted by the plant cultivation device (plant cultivation system) shown in  FIG. 2 . 
         FIG. 14  is a front view of the opening and closing unit adopted by the plant cultivation device (plant cultivation system) shown in  FIG. 2 . 
         FIG. 15  is a perspective view showing an inner structure of a seedling growing unit in another embodiment of the present invention. 
         FIG. 16  is a perspective view of a conveyance device incorporated in the seedling growing unit shown in  FIG. 15 . 
         FIG. 17  is a perspective view of a main part of a conveyance device incorporated in a seedling growing unit in another embodiment of the present invention. 
         FIG. 18A  and  FIG. 18B  are front views of a main part of the conveyance device shown in  FIG. 17 , wherein  FIG. 18A  shows a state where a power transmission member is removed, and  FIG. 18B  shows a state where the power transmission member is mounted. 
         FIG. 19  is a conceptual view of a plant cultivation device (plant cultivation system) according to another embodiment of the present invention. 
         FIG. 20  is a plan view showing a layout of a plant cultivation device (plant cultivation system) according to still another embodiment of the present invention. 
         FIG. 21A  and  FIG. 21B  are views showing a plant cultivation device according to still another embodiment of the present invention, wherein  FIG. 21A  is a perspective view showing the configuration of a unit plant cultivation device in a state where connecting members are removed from between seedling growing units,  FIG. 21B  is a perspective view showing the configuration of the unit plant cultivation device in a state where seedling growing units are connected to one by one. 
         FIG. 22A  and  FIG. 22B  are views of a plant cultivation device (plant cultivation system) according to still another embodiment of the present invention, wherein  FIG. 22A  is a front view showing a layout of the plant cultivation device (plant cultivation system) and  FIG. 22B  is a plan view of the plant cultivation device (plant cultivation system). 
         FIG. 23  is a cross-sectional perspective view as viewed from an A-A direction in  FIG. 22 . 
         FIG. 24  is a perspective view showing an inner structure of a seedling growing unit in still another embodiment of the present invention. 
         FIG. 25A  to  FIG. 25C  are views of the seedling growing unit shown in  FIG. 24 , wherein  FIG. 25A  is a front view showing the inner structure of the seedling growing unit shown in  FIG. 24 ,  FIG. 25B  is a partially enlarged cross-sectional view of a roof portion of the seedling growing unit, and  FIG. 25C  is an explanatory view for explaining the distribution of light emitting elements on an inner surface of the roof portion. 
         FIG. 26  is a perspective view of an air supply passage forming member incorporated in the seedling growing unit shown in  FIG. 24 . 
         FIG. 27  is an exploded cross-sectional perspective view of the air supply passage forming member shown in  FIG. 26 . 
         FIG. 28A  to  FIG. 28C  are cross-sectional views of the vicinity of an air supply port of the air supply passage forming member shown in  FIG. 26 , wherein  FIG. 28A  shows an air supply port in a fully open state,  FIG. 28B  shows the air supply port in a half open state, and  FIG. 28C  shows the air supply port in a fully closed state. 
         FIG. 29  is an exploded perspective view of a cultivation tray according to still another embodiment of the present invention. 
         FIG. 30  is a plan view of the cultivation tray shown in  FIG. 29 . 
         FIG. 31  is a perspective view of a lifting and lowering device adopted by a plant cultivation device (plant cultivation system) of still another embodiment of the present invention. 
         FIG. 32  is an exploded perspective view of the lifting and lowering device shown in  FIG. 31 . 
         FIG. 33A  to  FIG. 33E  are views showing an operation of the plant cultivation device in  FIG. 22 , and are front views and side views of the plant cultivation device showing steps of discharging a culture solution by inclining the cultivation tray immediately before taking out the cultivation tray toward a lifting and lowering device side from a cylindrical space. 
         FIG. 34A  to  FIG. 34C  are views showing an operation of the plant cultivation device in  FIG. 22 , and are front views and plan views of the plant cultivation device showing steps of taking out the cultivation tray toward the lifting and lowering device side from the cylindrical space. 
         FIG. 35D  and  FIG. 35E  are views showing an operation of the plant cultivation device in  FIG. 22  succeeding from the operation shown in  FIG. 34 , and are front views and plan views of the plant cultivation device showing steps of taking out the cultivation tray toward the lifting and lowering device side from the cylindrical space. 
         FIG. 36A  to  FIG. 36E  are perspective views showing a relationship between a conveyance-unit-side engaging portion and a drive-side engaging portion in the respective steps shown in  FIG. 34  and  FIG. 35 . 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, an embodiment of the present invention is described. 
     A plant cultivation device according to an embodiment of the present invention is configured such that seedling growing units  2  each having the same shape and the same structure as shown in  FIG. 4  are connected in series thus forming a continuous cylindrical space, and plants are cultivated in the cylindrical spaces. in the embodiment of the present invention, a structure which is formed by connecting the above-mentioned seedling growing units  2  in series forms a single unit plant cultivation device  1 . In this embodiment, as shown in  FIG. 1  and  FIG. 2 , a plural number of unit plant cultivation devices  1  described above are installed on a young seedling frame  103   a  and a grown seedling frame  103   b  and an accompanying facility is added thus forming a comprehensive plant cultivation device (plant cultivation system)  100 . 
     To distinguish both devices from each other, the former is referred to as “unit plant cultivation device  1 ” and the latter is referred to as “comprehensive plant cultivation device  100 ”. 
     The unit plant cultivation device  1  is, as shown in  FIG. 1 ,  FIG. 2 ,  FIG. 4  and  FIG. 5 , formed by connecting a plurality of seedling growing units  2  to each other in series. In  FIG. 4  and  FIG. 5 , in view of the relationship necessary for preparing these drawings, a total length of the individual seedling growing unit  2  is set shorter than an actual length. The length of the actual seedling growing unit  2  is longer as shown in  FIG. 1  and  FIG. 2 . 
     In the comprehensive plant cultivation device  100  of this embodiment, young seedling unit plant cultivation devices  1   a  each thrilled of young seedling growing units  2   a  and grown seedling unit plant cultivation devices  1   b  each formed of grown seedling growing units  2   b  are disposed in a mixed form. However, the young seedling growing unit  2   a  and the grown seedling growing unit  2   b  differ from each other only in height and have the same inner structure. Accordingly, in the description made hereinafter, the description is made by collectively referring to the young seedling growing unit  2   a  and the grown seedling growing unit  2   b  as “seedling growing unit  2 ”. The seedling growing unit  2  shown in  FIG. 3 ,  FIG. 4 ,  FIG. 5  and  FIG. 6  is the grown seedling growing unit  2   b.    
     The seedling growing unit  2  has a case  5  which has both ends thereof opened and can cover a peripheral surface of the seedling growing unit  2 . 
     The case  5  includes a roof portion  6  having an arcuate shape, a bottom surface portion  10 , and side surface portions  7 ,  8  having a vertical wall shape which connect the roof portion  6  and bottom surface portion  10  to each other. The case  5  has a longitudinal length of approximately 3 m. The case  5  has a width of approximately 1 m. Both ends of the case  5  are opened. One opening is referred to as an introducing opening  50  and the other opening is referred to as a discharging side opening  51 . 
     A pipe  36  is mounted on a ridge portion of the roof portion  6  as shown in  FIG. 9 . A plurality of small holes are formed in the pipe  36 . A cooling water collecting trough  37  is formed on cave portions of the roof portion  6 . 
     As shown in  FIG. 4  and  FIG. 5 , four inspection windows  11  are formed on one side wall surface portion  7  of the case  5 . The inspection windows  11  are transparent so that the situation in the case  5  is viewable from the outside. The inspection windows  11  are also operable and closable so that an operator can insert his hand into the inside of the case  5  through the inspection window  11 . 
     The case  5  is made of a colored resin or metal, and portions of the case  5  other than the inspection windows  11  are opaque. 
     An inner surface of the case  5  is coated with a reflective paint. Accordingly, the inner surface of the case  5  has reflectance of 40% or more using a sunbeam as the reference. It is desirable that the inner surface of the case  5  have reflectance of 60% or more, and it is recommendable that the inner surface of the case  5  have reflectance of 80% or more. 
     As shown in  FIG. 1 ,  FIG. 2  and  FIG. 4 , in a state where the case  5  is disposed on a frame (a young seedling frame  103   a  or a grown seedling frame  103   b ), the side surface portion  7  on which the inspection windows  11  are formed faces an operation aisle side, and the side surface portion  8  on a side opposite to the side surface portion  7  forms a back side. Accordingly, for the sake of convenience of the description, the side surface portion  7  on which the inspection windows  11  are formed is referred to as the aisle-side side surface portion  7  and the side opposite to the aisle-side side surface portion  7  is referred to as the back-side side surface portion  8 . 
     In this embodiment, as shown in  FIG. 6  and  FIG. 7 , inside the case  5 , a tray mounting base  12 , a conveyance device  15 , an illumination unit  16  and a water supply/discharge facility  17  are disposed. 
     The tray mounting base  12  can slidably move cultivation trays  38  described later in a state where the cultivation trays  38  are placed on the tray mounting base  12 . 
     The tray mounting base  12  is formed by bending a metal sheet, and has a placing portion  14  extending in a strip shape on both left and right ends thereof. 
     That is, the tray mounting base  12  is formed by bending both ends of a flat sheet in a U shape as shown in  FIG. 6  and  FIG. 8 , and is formed of a flat-plate-like base portion  12   a , leg portions  12   b  vertically raised from both ends of the base portion  12   a , and the placing portions  14  extending horizontally from the leg portions  12   b.    
     Fixed-side engaging projecting portions  18  are formed on the placing portion  14 . One end of the fixed-side engaging projecting portion  18  is swing ably fixed to the placing portion  14  of the tray mounting base  12  by a hinge not shown in the drawing and the other end side of the fixed-side engaging projecting portion  18  is biased so as to project outward from the placing portion  14 . A stopper not shown in the drawing which restricts the degree of opening of the fixed-side engaging projecting portion  18  is formed on the fixed-side engaging projecting portion  18 . Accordingly, the fixed-side engaging projecting portion  18  is openable about the hinge with limit degree of opening where an angle made by a surface which forms the placing portion  14  and the fixed-side engaging projecting portion  18  which projects in an inclined manner and in a cantilever manner becomes approximately 30 degrees to 60 degrees and the fixed-side engaging projecting portion  18  is not openable beyond the limit degree of opening. That is, the fixed-side engaging projecting portion  18  takes an inclined posture in a state where the other end side of the fixed-side engaging projecting portion  18  projects from the placing portion  14  of the tray mounting base  12 . When the fixed-side engaging projecting portion  18  receives an external force in a vertical direction, the fixed-side engaging projecting portion  18  sinks into the inside of the placing portion  14 , while when the external force is removed, the other end side of the fixed-side engaging projecting portion  18  projects outward from the placing portion  14  again. The fixed-side engaging projecting portion  18  is a projection having a non-reversible function. 
     The conveyance device  15  is formed of two rows of pressing member connecting bodies  20 . The pressing member connecting body  20  is formed by joining a plurality of pressing members  22  by string bodies  23  such as wires, chains or belts. In this embodiment, four pressing members  22  are joined to each other at an interval by the wires. 
     The pressing member  22  has a block-shaped body portion  24 , and a moving-side engaging projecting portion (tray facing engaging portion)  21  is mounted on each body portion  24 . The moving-side engaging projecting portion  21  has substantially the same structure and function as the fixed-side engaging projecting portion  18  described above. That is, one end of the moving-side engaging projecting portion  21  is swingably fixed to the body portion  24  by a hinge not shown in the drawing and the other end side of the moving-side engaging projecting portion  21  is biased so as to project outward from the body portion  24 . A stopper not shown in the drawing which restricts the degree of opening of the moving-side engaging projecting portion  21  is formed on the moving-side engaging projecting portion  21 . Accordingly, the moving-side engaging projecting portion  21  is openable about the hinge with limit degree of opening where an angle made by a surface of the pressing member  22  and the moving-side engaging projecting portion  21  which projects in an inclined manner and in a cantilever manner becomes approximately 30 degrees to 60 degrees and the moving-side engaging projecting portion  21  is not openable beyond the limit degree of opening. That is, the moving-side engaging projecting portion  21  takes an inclined posture in a state where the other end side of the moving-side engaging projecting portion  21  projects from the body portion. 
     When the moving-side engaging projecting portion  21  receives an external force in a vertical direction, the moving-side engaging projecting portion  21  sinks into the inside of a main part of the body portion  24 , while when the external force is removed, the other end side of the moving-side engaging projecting portion  21  projects outward from the body portion  24  again. The moving-side engaging projecting portion  21  is a projection having a non-reversible function. 
     While the pressing members  22  are connected to each other by the string bodies  23  as described above, an engaging ring  27  is mounted on end portions of the string bodies  23  at both ends of the conveyance device  15 . 
     The pressing member connecting bodies  20  in two rows are arranged parallel to each other with a fixed distance therebetween. To be more specific, the respective pressing member connecting bodies  20  are disposed in a region surrounded by the leg portions  12   b  of the tray mounting base  12  and in the vicinity of inner end portions of the placing portions  14 . 
     The illumination unit  16  is formed of a fluorescent lamp or an LED (light emitting diode) and emits light of a wavelength suitable for growing plants. 
     The water supply/discharge facility  17  is formed of: a supply-side pipe  31  for supplying a culture solution to the cultivation trays  38 ; and a collecting-side pipe  32  for collecting a culture solution overflown from the cultivation trays  38 . 
     The supply-side pipe  31  is formed of: one main pipe  33 ; and a plurality of branch pipes  35  branched from the main pipe  33 . 
     The collecting-side pipe  32  includes a culture solution collecting trough  46 . 
     As shown in  FIG. 10 , the cultivation tray  38  is formed of a container portion  40  having a quadrangular shape as viewed in a plan view, and a seedling holding plate  41 . 
     The container portion  40  is a tray having a structure which prevents leakage of water and has an open-ended upper surface. The container portion  40  is formed so as to have a slightly larger area in the vicinity of the opening portion. 
     As shown in  FIG. 10 , an uneven shape is formed on a bottom of the container portion  40 . That is, projecting portions  42  and recessed groove portions  43  are formed on the bottom of the container portion  40  such that the projecting portions  42  and the recessed groove portions  43  are alternately firmed in parallel. Vertical wall portions of the recessed groove portions  43  function as engaging portions  45  as described later. 
     The seedling holding plate  41  is formed of a plate in which a plurality of openings are termed. 
     Next, a positional relationship between the respective members which form the seedling growing unit  2  and a positional relationship of the cultivation tray  38  are described. 
     The tray mounting base  12  and the conveyance device  15  are disposed at the position of the bottom in the case  5 . Further, as described previously, the pressing member connecting bodies  20  in two rows are disposed at a portion inside the tray mounting base  12 . 
     The tray mounting base  12  is slightly inclined in a direction which intersects with a longitudinal direction in the case  5 . 
     That is, the placing portions  14  of the tray mounting base  12  extending in two rows are slightly inclined laterally such that the aisle-side side surface portion  7  is lower than the back-side side surface portion  8 . 
     Accordingly, when the cultivation tray  38  is placed on the tray mounting base  12  as shown in  FIG. 9 , the cultivation tray  38  is slightly inclined in the lateral direction. 
     The conveyance devices  15  are connected to each other by a power transmission member  28  as described later, and can make the pressing members  22  travel in a longitudinal direction (a direction which connects the openings at both ends) of the case  5  by starting a motor not shown in the drawing. 
     The main pipe  33  of the supply-side pipe  31  of the water supply/discharge facility  17  is disposed in the vicinity of an upper end of the back-side side surface portion  8 . 
     The branch pipes  35  of the water supply/discharge facility  17  open above the tray mounting base  12 . 
     The culture solution collecting trough  46  of the water supply/discharge facility  17  is mounted at a lower position in a height direction in the vicinity of the aisle-side side surface portion  7 . 
     The illumination units  16  are mounted on an inner side of the roof portion  6  inside the case  5 . Mounting positions of the illumination units  16  are positions at which the illumination units  16  can irradiate the cultivation tray  38  with light on the tray mounting base  12 . 
     Next, the unit plant cultivation device  1  is described. 
     The unit plant cultivation device  1  is formed by connecting the plurality of seedling growing units  2  in series. The plurality of seedling growing units  2  have the same shape and structure, and an introducing opening  50  of the case  5  of another seedling growing unit  2  is connected to a discharge-side opening  51  of the case  5  of one seedling growing unit  2 . 
     In an actual configuration, the cases  5  of the seedling growing units  2  are made to face each other with a gap formed therebetween, and the connecting member  55  is mounted between the cases  5  so as to connect the cases  5  to each other. As shown in  FIG. 4  and  FIG. 5 , the connecting member  55  is formed of a belt, and as shown in  FIG. 4  and  FIG. 12 , one end of the connecting member  55  is fixed to pillars  107  of the young seedling frame  103   a  and the grown seedling frame  103   b  respectively. A width of the connecting member  55  is shorter than a width of the case  5 . To be more specific, the width of the connecting member  55  is approximately 30 cm to 80 cm. 
     The connecting member  55  is formed in a belt shape and is wound around a gap portion formed between the cases  5 . 
     That is, the cases  5  of the seedling growing units  2  are arranged linearly as shown in  FIG. 4 ,  FIG. 5A  and  FIG. 5B . A gap which allows an operator&#39;s hand to pass therethrough is formed or opened between the discharging-side opening  51  of the case  5  of one seedling growing unit  2  and the introducing opening  50  of the case  5  of another seedling growing unit  2  disposed adjacently to the one seedling growing unit  2 . To be more specific, the seedling growing units  2  are disposed such that discharging-side opening  51  of the case  5  of the one seedling growing unit  2  and the end portion of the neighboring seedling growing unit  2  face each other with a gap of approximately 10 cm to 40 cm formed therebetween. 
     Wires, pipes and the like are connected between the seedling growing units  2  disposed adjacently to each other as shown in  FIG. 8 . 
     To be more specific, the main pipes  33  of the supply-side pipes  31  of the water supply/discharge facility  17  are connected to each other. The cooling water collecting trough  37  of the roof portions  6  are connected to each other between the seedling growing units  2  (not shown in the drawing). Power supply wires of the illumination units  16  are connected to each other between the seedling growing units  2  (not shown in the drawing). 
     Water supply/discharge facilities  17  disposed inside the respective cases  5  are connected to each other by couplers or the like not shown in the drawing thus forming a series of water supply/discharge lines. That is, the main pipe  33  of the supply-side pipe  31  in the seedling growing unit  2  has both ends thereof connected to the main pipes  33  of the neighboring seedling growing units  2  thus forming a series of water supply lines. 
     In the same manner, the culture solution collecting trough  46  of the seedling growing unit  2  has both ends thereof connected to the culture solution collecting troughs  46  of the neighboring seedling growing units  2  thus forming a series of water discharge lines. 
     When necessary, the following members or parts are disposed between the seedling growing units  2  disposed adjacently to each other.
     (1) connecting unit and/or merging unit of supply passages of culture solution   (2) branching unit for branching branch pipe from main pipe through which culture solution is supplied   (3) connecting unit and/or merging unit of discharge passages of culture solution   (4) connecting unit and/or merging unit of electric wiring of illumination   (5) branching units leading to respective illuminations from main line of electric wiring of illumination   (6) connecting unit and/or merging unit of air conditioning ducts   (7) branching unit of air conditioning duct   (8) connecting unit and/or merging unit of carbon dioxide pipes   (9) branching unit of carbon dioxide pipe   (10) valve   (11) distributer   (12) fuse   

     Further, the pressing member connecting bodies  20  disposed inside the cases  5  disposed adjacently to each other are connected to each other. To be more specific, the engaging rings  27  formed on end portions of the pressing member connecting bodies  20  are connected to each other by the power transmission member  28 . In this embodiment, the power transmission member  28  is a connecting fitting which connects the engaging rings  27  to each other and transmits power in an axial direction. 
     Both ends of the pressing member connecting bodies  20  connected in series are wrapped around rolls  30   a ,  30   b.    
     As a result, the conveyance devices  15  in the cases  5  are connected to each other so that the conveyance devices  15  in the plurality of cases  5  form a series of conveyance units  19  as shown in  FIG. 11 . 
     The rolls  30   a ,  30   b  can be rotated in both normal and reverse directions by motors not shown in the drawing. Due to the rotation of the rolls  30   a ,  30   b , the pressing member connecting bodies  20  are moved so that the pressing members  22  are linearly moved inside the cases  5 . 
     A longitudinal end portion of the tray mounting base  12  in one case  5  and a longitudinal end portion of the tray mounting base  12  in another case  5  disposed adjacently to the one case  5  are arranged at positions disposed close to each other so that the placing portions  14  of the tray mounting bases  12  in the plurality of cases  5  form a series of tray traveling surfaces. 
     The connecting member  55  is mounted between the cases  5  of two seedling growing units  2  from the outside. 
     By connecting the cases  5  of the plurality of seedling growing units  2  by the connecting members  55 , a continuous cylindrical space  60  is formed inside the cases  5 . Any suitable door or lid may be disposed on both ends of the unit plant cultivation device  1 . Accordingly, the cylindrical spaces  60  form an approximately closed space. However, the degree of sealing of the cylindrical spaces is not so high. 
     A power supply line  25  is connected to the illumination units  16  in each case  5  so that turning-on and turning-off of the illumination units  16  can be performed for each seedling growing unit  2 . Illuminance can be adjusted also for each case  5 . A volume (not shown in the drawing) for adjusting illuminance and a fuse are disposed between the cases  5  of two seedling growing units  2 . 
     While the cultivation trays  38  are placed on the tray mounting base  12 , the branch pipes  35  of the above-mentioned water supply/discharge facility  17  open above the cultivation tray  38 . With such a configuration, when a culture solution is discharged from the branch pipes  35 , all discharged culture solution enters the cultivation trays  38 . 
     The cultivation tray  38  takes an inclined posture and hence, a surplus culture solution overflows from sides of the cultivation tray  38  to aisle-side side surface portion  7  sides. On the other hand, the culture solution collecting troughs  46  are disposed at the low position in a height direction in the vicinity of the aisle-side side surface portions  7  and hence, an overflown culture solution is collected by the culture solution troughs  46 . 
     Pipes  36  mounted on ridge portions of the roof portions  6  are connected to each other thus forming a series of cooling water supply lines. 
     The cooling water supply lines are provided for preventing an excessive elevation of a temperature in the cylindrical space  60  which may be caused by the illumination units  16  disposed in the respective cases  5 . The cooling water supply line discharges water through holes formed in the pipe  36  and cools the roof portion  6  of the case  5 . Discharged water flows on the roof portion  6  having an arcuate shape and is collected by the cooling water collecting trough  37 . 
     Next, functions of the unit plant cultivation device  1  are described. 
     In the unit plant cultivation device  1 , the cultivation trays  38  are inserted into the continuous cylindrical space  60  from one end side (upstream side end portion). Seedlings of plants such as lettuces are planted in advance in the cultivation tray  38 . In this embodiment, four cultivation trays  38  are placed on the tray mounting base  12  of one seedling growing unit  2 . Although the number of cultivation trays  38  which can be inserted into one seedling growing unit  2  is arbitrary, it is recommendable that the number of insertable cultivation trays  38  be approximately two to six. 
     As shown in  FIG. 7  and  FIG. 9 , the cultivation trays  38  are placed on the tray mounting base  12  in the case  5  in an inclined posture. 
     Then, a culture solution is supplied to the cultivation tray  38  by the supply-side pipe  31  of the water supply/discharge facility  17 , and an overflown culture solution is recovered by the culture solution collecting trough  46 . Accordingly, the inside of the cultivation tray  38  is constantly filled with a culture solution. 
     Light necessary for growth of seedlings is supplied by the illumination units  16 . In this embodiment, since an inner surface of the case  5  is coated with a reflective paint, light which impinges on the inner wall of the case  5  is also reflected and is irradiated to the seedlings. 
     A temperature, a humidity and a carbon dioxide concentration in the cylindrical space  60  are adjusted by an air conditioning facility or the like not shown in the drawings. 
     To achieve an object of maintaining an environment in the cylindrical space  60  by preventing the intrusion of outside air and an object of preventing the intrusion of dust in the cylindrical space  60 , it is desirable to maintain a slightly positive pressure in the cylindrical space  60  compared to an atmospheric pressure. 
     The cultivation tray  38  placed in the cylindrical space  60  is moved to a downstream side each time that a fixed time elapses. For example, every 24 hours elapse, the conveyance device  15  is operated so as to move the cultivation tray  38  from one seedling growing unit  2  to another seedling growing unit  2  disposed adjacently to the one seedling growing unit  2  on a discharge side opening  51  side. 
     Next, the manner of operation of moving the cultivation tray  38  is described with reference to  FIG. 11 . 
     The cultivation tray  38  is placed on the tray mounting base  12  as described, and the cultivation tray  38  is slidably movable on the placing portions  14  of the tray mounting base  12 . 
     Two rows of pressing member connecting bodies  20  of the conveyance device  15  are disposed inside the placing portions  14  of the tray mounting base  12 , and the side portions of the cultivation tray  38  are disposed over the pressing member connecting bodies  20  so as to cover the pressing member connecting bodies  20  as shown in  FIG. 7 . 
     In such a state, the rolls  30   a ,  30   b  are rotated so as to operate the pressing member connecting bodies  20  of the conveyance device  15  in an arrowed direction shown in  FIG. 11A . That is, the motor not shown in the drawing is rotated so as to move the pressing members  22  of the conveyance device  15  from the introducing opening  50  side to the discharging side opening  51  side in the case  5 . 
     During such operations, the moving-side engaging projecting portions  21  of the conveyance device  15  project and take an inclined posture as shown in  FIG. 11A . A bottom of the cultivation tray  38  is formed in an uneven shape as shown in  FIG. 10 . 
     Accordingly, when the pressing members  22  of the conveyance device  15  are moved from the introducing opening  50  side to the discharging side opening  51  side, the projecting portions of the moving-side engaging projecting portions  21  engage with the vertical wall portions (engaging portions  45 ) of the recessed groove portions  43 , and move the cultivation trays  38  from the introducing opening  50  side to the discharging side opening  51  side as shown in  FIG. 11B . 
     As a result, inside each seedling growing unit  2 , the respective cultivation trays  38  move toward a downstream side. Then, the cultivation tray  38  positioned on a most downstream side of each seedling growing unit  2  enters the neighboring seedling growing unit  2 . 
     That is, the cultivation tray  38  is transferred from the tray mounting base  12  of the original seedling growing unit  2  to the tray mounting base  12  of the neighboring seedling growing unit  2  on a downstream side, and moves striding over the seedling growing units  2 . That is, in this embodiment, the conveyance devices  15  in the respective cases  5  form the series of conveyance units  19 , and the seedling growing units  2  move downward in a striding manner over the seedling growing units  2  by the conveyance units  19 . 
     In this embodiment, the cultivation trays  38  in each seedling growing unit  2  are sequentially fed out to the preceding seedling growing unit  2  by the series of conveyance units  19 . A new cultivation tray  38  is carried in the seedling growing unit  2  from an upstream side. 
     Thereafter, as shown in  FIG. 11C , the motor not shown in the drawing is rotated so as to rotate the rolls  30   a ,  30   b  in the reverse direction so that the conveyance device  15  is moved in the reverse direction whereby the pressing members  22  are moved from the discharging side opening  51  side to the introducing opening  50  side. 
     In such an operation, while the moving-side engaging projecting portion  21  of the conveyance device  15  impinges on the bottom of the cultivation tray  38 , the moving-side engaging projecting portion  21  is in an inclined posture and hence, the moving-side engaging projecting portion  21  is brought into contact with the cultivation tray  38  from a lower side of the inclination. Since the inclined surface of the moving-side engaging projecting portion  21  is brought into contact with the cultivation tray  38 , the moving-side engaging projecting portion  21  is pushed down in a downward direction by a -vertical-direction component force generated by inclination. In such a state, although the moving-side engaging projecting portion  21  is biased so as to project toward the outside from the body portion, when the moving-side engaging projecting portion  21  receives an external force in a vertical direction, the moving-side engaging projecting portion  21  sinks into the body portion  24  of the pressing member  22 . 
     Accordingly, as shown in  FIG. 11C  and  FIG. 11D , the moving-side engaging projecting portion  21  passes below the projecting portion of the cultivation tray  38 , and the new cultivation tray  38  and the moving-side engaging projecting portion  21  return to the relationship shown in  FIG. 11A . 
     As the pressing member  22  moves from the discharging side opening  51  side to the introducing opening  50  side, the cultivation tray  38  receives a force directed from the discharging side opening  51  side to the introducing opening  50  side. However, the fixed-side engaging projecting portion  18  is formed on the placing portion  14 , and the fixed-side engaging projecting portion  18  has a reverse operation stopping function by projecting outward from the placing portion  14  thus preventing the cultivation tray  38  from moving toward the introducing opening  50  side from the discharging side opening  51  side. 
     In the unit plant cultivation device  1 , the cultivation tray  38  is fed from a start end to a terminal end with spending days ranging from approximately 10 days to 30 days. Then, the cultivation tray  38  is taken out at the terminal end, and grown plants are harvested or the cultivation tray  38  is carried in another unit plant cultivation device  1  again so as to make seedlings grow further. 
     That is, the cultivation tray  38  in which seedlings are planted is inserted into the seedling growing unit  2  positioned at the start end of the unit plant cultivation device  1 , leaves of seedlings are irradiated with light by turning on the illumination unit  16  so that the seedlings are grown by absorbing a culture solution in the cultivation tray  38  through roots of the seedlings. Then, the conveyance device  15  is driven so as to slowly move the cultivation tray  38  inside the cylindrical space  60 . When the cultivation tray  38  reaches the terminal end of one unit plant cultivation device  1  or when the cultivation tray  38  passes through the plurality of unit plant cultivation devices  1  and reaches the terminal end, the seedlings are grown to an extent that the seedlings are edible and hence, the seedlings are harvested from the cultivation tray  38  and are shipped. 
     In the unit plant cultivation device  1  according to this embodiment, in adjusting a temperature of the unit plant cultivation device  1 , water is auxiliarily discharged from the pipes  36  of the cooling water supply line so that excessive temperature elevation caused by the illumination units  16  is suppressed. 
     Next, the comprehensive plant cultivation device (plant cultivation system)  100  is described. 
     The comprehensive plant cultivation device  100  includes  24  unit plant cultivation devices  1 , a tray carrying-in device  101 , a tray exchange device  102 , a tray carrying-out device  112 , an open/close member  118 , and a tray conveyer  140 . The comprehensive plant cultivation device  100  also includes an air conditioning facility  122  and a carbon dioxide supply facility  123 . 
     Regarding breakdown of 24 unit plant cultivation devices  1 , 24 unit plant cultivation devices  1  are formed of 16 young seedling unit plant cultivation devices  1   a  each of which is formed of the young seedling growing units  2   a , and 8 grown seedling unit plant cultivation devices  1   b  each of which is formed of the grown seedling growing units  2   b.    
     The young seedling unit plant cultivation device  1   a  and the grown seedling unit plant cultivation device  1   b  are mounted on the young seedling frame  103   a  and the grown seedling frame  103   b  respectively thus forming a group of young seedling unit plant cultivation devices  105  and a group of grown seedling unit plant cultivation devices  106 . 
     The group of young seedling unit plant cultivation devices  105  is formed by arranging  16  young seedling unit plant cultivation devices  1   a  in a matrix of two rows and eight stages on the young seedling frame  103   a , while the group of grown seedling unit plant cultivation devices  106  is formed by arranging  8  grown seedling unit plant cultivation devices  1   b  in a matrix of 2 rows and 4 stages on the grown seedling frame  103   b.    
     The arrangement of the respective devices in the comprehensive plant cultivation device  100  is shown in  FIG. 2 . From the left end in  FIG. 2 , the tray carrying-in device  101 , the group of young seedling unit plant cultivation devices  105 , the tray exchange device  102 , the group of grown seedling unit plant cultivation devices  106  and the tray carrying-out device  112  are sequentially disposed. The open/close member  118  is mounted on each of both ends of the group of young seedling unit plant cultivation devices  105  and each of both ends of the group of grown seedling unit plant cultivation devices  106  respectively. 
     The tray conveyer  140  is disposed above the group of young seedling unit plant cultivation devices  105  and the group of grown seedling unit plant cultivation devices  106 . The air conditioning facility  122  and the carbon dioxide supply facility  123  are disposed below the group of young seedling unit plant cultivation devices  105  and the group of grown seedling unit plant cultivation devices  106 . 
     Power supply cables, outer pipes which form a flow passage for a culture solution, carbon dioxide pipes, air conditioning ducts, signal lines and the like are also disposed below the group of young seedling unit plant cultivation devices  105  and the group of grown seedling unit plant cultivation devices  106 . 
     The following members and parts are disposed below the group of young seedling unit plant cultivation devices  105  and the group of grown seedling unit plant cultivation devices  106  when necessary.
     (1) power supply cable   (2) flow passage for culture solution   (3) carbon dioxide pipe   (4) air conditioning duet   (5) signal lines   

     As described previously, the young seedling growing unit  2   a  and the grown seedling growing unit  2   b  differ from each other only in a total height, and are equal with respect to other structures and functions. 
     Accordingly, the young seedling frame  103   a  and the grown seedling frame  103   b  differ from each other only in the number of stages and a height of each stage, and are equal with respect to other structures. 
     In view of the above, the grown seedling frame  103   b  is described hereinafter by representing both frames  103   a ,  103   b.    
     The grown seedling frame  103   b  is a shelf which forms the group of grown seedling unit plant cultivation devices  106  by disposing 8 grown seedling unit plant cultivation devices  1   b  in a matrix of 2 rows and 4 stages. As shown in  FIG. 12 , the grown seedling frame  103   b  includes a plurality of pillars  107  and a plurality of holding members  108 . 
     The respective pillars  107  are connected to each other at a plurality of height positions. All of respective pillars  107  are self-standing. The holding members  108  are mounted on the pillar  107 . As shown in  FIG. 12 , the holding member  108  has bottom support portions  110   a ,  110   b ,  110   c , and  110   d  in four areas around the pillar  107 . The respective bottom support portions  110   a ,  110   b ,  110   c , and  110   d  are disposed horizontally. 
     In the grown seedling frame  103   b , the holding members  108  are mounted in 4 stages for disposing the grown seedling unit plant cultivation devices  1   b  in a matrix of 2 rows and 4 stages. 
     A distance between the holding members  108  mounted on each pillar  107  is set slightly higher than a height of the grown seedling growing unit  2   b.    
     A distance between the respective pillars  107  is set equal to a length of the grown seedling growing unit  2   b . A connecting member  55  is mounted on the respective stages to which the holding members  108  of each pillar  107  are mounted. 
     Rails  111   a ,  111   b  are mounted on upper portions on side surface sides of the grown seedling frame  103   b , and the lifting and lowering device  115  are mounted on the rails  111   a ,  111   b . The lifting and lowering device  115  travels along the rails  111   a ,  111   b  manually or by electric power. 
     The lifting and lowering device  115  is configured such that a lifting and lowering wires  116  are wound around a roller  141  rotated by a motor not shown in the drawing. 
     A fork member  142  is suspended by the lifting and lowering wires  116 . The fork member  142  has an approximately “L”-shaped side surface. Accordingly, the fork member  142  has a fork portion  145  where a plurality of horizontal plates  143  project in a cantilever manner as fork of a forklift. 
     That is, the fork member  142  is formed such that two horizontal plates  143  disposed parallel to each other are mounted on a connecting portion  146  in a cantilever manner, and extending portions  144  extend from the connecting portion  146  in an oblique upward direction. A width of the fork portion  145  is set shorter than a total length of the seedling growing unit  2 . 
     The lifting and lowering wires  116  are mounted on distal ends of the extending portions  144 . 
     The lifting and lowering wires  116  are mounted at a position where the fork portion  145  can maintain a horizontal posture. 
     As shown in  FIG. 13 , the open/close member  118  is formed such that winding rollers  146   a ,  146   b  are disposed horizontally in a vertically spaced-apart manner from each other and in parallel to each other, and a sheet  147  is wound around two winding rollers  146   a ,  146   b . An opening  148  is formed in a portion of the sheet  147 . 
     The winding rollers  146   a ,  146   b  are respectively formed of a type of roller where motor is incorporated in a roller body. Due to the rotation of the incorporated motor, the winding rollers  146   a ,  146   b  are rotated. As a result, the sheet  147  is moved so that the position of the opening  148  is changed. 
     The tray conveyer  140  is formed of a roller conveyer. 
     In this embodiment, as shown in  FIG. 3 , one grown seedling growing unit  2   b  is placed on one of the bottom support portions  110   a ,  110   b ,  110   c  and  110   d  disposed around the pillar  107  of the holding member  108  as the center and on one of the bottom support portions  110   a ,  110   b ,  110   c  and  110   d  of the holding member  108  of the neighboring pillar  107 . That is, in this embodiment, a unit mounting space is formed between the pillars  107  disposed adjacently to each other in a length direction and between the upper and lower holding members  108  in a height direction. 
     In a state where the grown seedling growing unit  2   b  is placed in the unit mounting space, the cases  5  of the grown seedling growing units  2   b  disposed adjacently to each other are made to face each other with a gap formed therebetween, and the connecting member  55  is mounted on the facing portions. 
     The group of grown seedling unit plant cultivation devices  106  is formed such that the grown seedling growing units  2   b  are mounted in the respective unit mounting spaces of the grown seedling frame  103   b  such that the grown seedling unit plant cultivation devices  1   b  are arranged in a matrix of 2 rows and 4 stages. 
     The steps of mounting the grown seedling growing units  2   b  in the unit mounting spaces are described hereinafter. 
     That is, the grown seedling growing units  2   b  are placed on the fork portion  145  of the fork member  142  one by one, and the lifting and lowering device  115  is lifted or lowered and, at the same time, the lifting and lowering device  115  is made to travel along the rails  111   a ,  111   b  so as to move the grown seedling growing unit  2   b  to the front of the unit mounting space in which the grown seedling growing unit  2   b  is to be mounted. At this stage of operation, the height of the fork portion  145  is higher than the holding member  108  mounted on the pillar  107 . 
     Then, the lifting and lowering wires  116  are brought into an inclined posture by pushing the fork member  142  so that the fork portion  145  is inserted between the holding members  108 . Subsequently, the fork member  142  is lowered by operating the lifting and lowering device  115 , and the grown seedling growing unit  2   b  is transferred to the holding member  108  from the fork portion  145 . 
     The group of young seedling unit plant cultivation devices  105  is formed by mounting the young seedling unit plant cultivation devices  1   a  on the young seedling frame  103   a  in a matrix of two rows and eight stages. Although the young seedling frame  103   a  differs from the above-mentioned grown seedling frame  103   b  with respect to the number of holding members  108  and a distance between the holding members  108 , the young seedling frame  103   a  and the grown seedling frame  103   b  are equal with respect to other constitutions and hence, the detailed description of the young seedling frame  103   a  is omitted. 
     All of the tray carrying-in device  101 , the tray exchange device  102 , and the tray carrying-out device  112  are formed of a lifting and lowering elevator for conveying trays, and are respectively formed of two sets of lifting and lowering tables  125 ,  126 ,  127 . The tray carrying-in device  101 , the tray exchange device  102 , and the tray carrying-out device  112  are respectively formed of a lifting and lowering device. 
     All of the tray carrying-in device  101 , the tray exchange device  102 , and the tray carrying-out device  112  are configured such that the respective lifting and lowering tables  125 ,  126 ,  127  are lifted or lowered by lifting and lowering chains or the like not shown in the drawing. 
     Roller conveyer devices  130 ,  131 ,  132  are mounted on the lifting and lowering tables  125 ,  126 ,  127  respectively, and hence, the cultivation trays  38  on the lifting and lowering table  125 ,  126 ,  127  can be carried in or carried out by power. 
     The open/close member  118  is disposed at each of both ends of the group of young seedling unit plant cultivation devices  105  and at each of both ends of the group of grown seedling unit plant cultivation devices  106  respectively. The opening formed on the end portion of each unit plant cultivation device  1  is sealed by the sheet  147  of the open/close member  118 . 
     The end portion of the unit plant cultivation device  1  can be opened by making the opening  148  formed in the sheet  147  of the open/close member  118  aligned with the position of the end portion of the unit plant cultivation device  1 . 
     In the comprehensive plant cultivation device  100  according to this embodiment, young seedlings are grown to a certain size in the former half portion of the comprehensive plant cultivation device  100 , and the seedlings are grown to a size which allows harvesting in the latter half portion of the comprehensive plant cultivation device  100 . 
     That is, in the comprehensive plant cultivation device  100  of this embodiment, young seedlings are planted in the cultivation trays  38  in an operation area not shown in the drawing. 
     Then, the cultivation tray  38  in such a state is placed on the lifting and lowering table  125  of the tray carrying-in device  101 . In this embodiment, the roller conveyer device  130  is mounted on the lifting and lowering table  125  and hence, by starting the roller conveyer device  130 , it is possible to pull the cultivation tray  38  onto the lifting and lowering table  125  from the outside. 
     Then, the lifting and lowering table  125  is lifted to a predetermined height, and the cultivation tray  38  is discharged from the lifting and lowering table  125  by starting the roller conveyer device  130  thus carrying the cultivation tray  38  into the young seedling growing unit  2   a  at a start end portion of any one of the young seedling unit plant cultivation devices  1   a . As described previously, the open/close member  118  is disposed on the introducing opening  50  of the young seedling growing unit  2   a  at the start end portion of the young seedling unit plant cultivation device  1   a , and the start end portion of the young seedling unit plant cultivation device  1   a  is opened by making the opening  148  formed in the sheet  147  of the open/close member  118  aligned with the position of an end portion of the unit plant cultivation device  1 . Then, the cultivation tray  38  is introduced into the young seedling growing unit  2   a  from the opening  148  formed in the sheet  147  and, thereafter, the end portion of the young seedling growing unit  2   a  is closed by moving the position of the opening  148  formed in the sheet  147 . 
     The specific young seedling unit plant cultivation device  1   a  into which the cultivation tray  38  is inserted is programed in advance. A series of operations performed after the cultivation tray  38  is placed on the lifting and lowering table  125  of the tray carrying-in device  101  is automatically performed. 
     That is, the lifting and lowering table  125  is automatically lifted and stopped at a predetermined position. The sheet  147  is moved so as to open the end portion of the young seedling unit plant cultivation device  1   a . The roller conveyer device  130  is started so that the cultivation tray  38  is introduced into the young seedling growing unit  2   a  and, thereafter, the end portion of the young seedling unit plant cultivation device  1   a  is closed. 
     The cultivation trays  38  are inserted into each young seedling unit plant cultivation device  1   a , and young seedlings are grown in the respective young seedling unit plant cultivation devices  1   a  until the young seedlings are grown up to a certain size. 
     That is, seedlings are grown such that the illumination units  16  in the young seedling growing unit  2   a  are turned on so as to irradiate leaves of the seedlings with light, and the seedlings are made to absorb a culture solution in the cultivation tray  38  through roots of the seedlings. The conveyance device  15  is driven so as to slowly move each tray  38  in the cylindrical space  60  from the upstream side toward the downstream side. That is, each tray  38  strides over the young seedling growing units  2   a , and is sequentially moved toward the downstream side. When the cultivation tray  38  reaches a terminal end of the young seedling unit plant cultivation device  1   a , the seedlings are grown to have a height which allows the seedlings to almost reach a ceiling of the case  5 . 
     The cultivation tray  38  which reaches the terminal end of the young seedling unit plant cultivation device  1   a  is placed on a lifting and lowering table  126  of the tray exchange device  102 , and is transferred to the grown seedling unit plant cultivation device  1   b.    
     That is, the open/close member  118  is disposed on the discharging side opening  51  of the young seedling growing unit  2   a  at the terminal end of the young seedling unit plant cultivation device  1   a . The position of the opening  148  of the open/close member  118  is moved so as to open the terminal end of the young seedling unit plant cultivation device  1   a . The cultivation tray  38  is discharged from the young seedling growing unit  2   a , and is placed on the lifting and lowering table  126  of the tray exchange device  102 . 
     Then, the tray exchange device  102  is lifted and lowered in accordance with a program inputted in advance, and is stopped at a height of the specific grown seedling unit plant cultivation device  1   b.    
     Thereafter, a start end portion of the grown seedling unit plant cultivation device  1   b  is automatically opened by the open/close member  118  disposed on the introducing opening  50  of the grown seedling growing unit  2   b  at the start end portion of the grown seedling unit plant cultivation device  1   b . The roller conveyer device  131  of the lifting and lowering table  126  is started so as to introduce the cultivation tray  38  into the grown seedling growing unit  2   b  and, thereafter, the start end portion of the grown seedling unit plant cultivation device  1   b  is automatically closed. 
     After the start end portion of the grown seedling unit plant cultivation device  1   b  is closed, the seedlings are grown in the grown seedling unit plant cultivation device  1   b . The case  5  of the grown seedling growing unit  2   b  forming the grown seedling unit plant cultivation device  1   b  has a tall height so that the seedlings can be grown to a tall height. 
     The cultivation tray  38  which reaches a terminal end of the grown seedling unit plant cultivation device  1   b  is placed on a lifting and lowering table  127  of the tray carrying-out device  112 , and the lifting and lowering table  127  is lowered and, thereafter, the cultivation tray  38  is discharged from the comprehensive plant cultivation device  100  by the roller conveyer device  132 . 
     Such a series of operations is also performed automatically. 
     That is, the open/close member  118  is disposed on the discharging side opening  51  of the grown seedling growing unit  2   b  at the terminal end of the grown seedling unit plant cultivation device  1   b . The open/close member  118  is automatically operated so as to open the terminal end of the grown seedling unit plant cultivation device  1   b . The cultivation tray  38  is discharged from the grown seedling growing unit  2   b , and is placed on the lifting and lowering table  127  of the tray carrying-out device  112 . The lifting and lowering table  127  is lowered and, thereafter, the cultivation tray  38  is discharged from the comprehensive plant cultivation device  100  by the roller conveyer device  132 . 
     In the comprehensive plant cultivation device  100  of this embodiment, a space where plants are grown is limited to the cylindrical space  60  so that a space where a temperature, humidity, carbon dioxide and the like are required to be controlled is narrow. Accordingly, a small energy is required to control the temperature, the humidity, the carbon dioxide and the like. 
     When a harmful insect invades the unit plant cultivation device  1 , extermination of the harmful insect can be performed in a state where an operation of one unit plant cultivation device  1  is stopped and hence, damage does not spread. 
     In the comprehensive plant cultivation device  100  of this embodiment, a space which should be kept clean is limited to the cylindrical space  60  and hence, unlike a conventional plants factory, it is unnecessary to take a strict countermeasure for prevention of invasion of harmful insects, or to install a large-scaled cleaning device. 
     Accordingly, crops can be produced by installing the comprehensive plant cultivation device  100  of this embodiment in an abandoned factory or a warehouse. 
     In the comprehensive plant cultivation device  100  of this embodiment, a space where plants are grown is limited to the cylindrical space  60  and hence, different plants may be grown in one comprehensive plant cultivation device  100 . 
     In installing the comprehensive plant cultivation device  100 , the seedling growing units  2  and the frames  103  are manufactured in a factory in advance. These members and units are transported to an installation site, and the comprehensive plant cultivation device  100  is completed by assembling the members and the units to each other at the installation site. Accordingly, an amount of operations to be performed at the installation site can be reduced. 
     The same goes for the transfer of the comprehensive plant cultivation device  100 . The seedling growing units  2  are removed and conveyed. In the same manner, the frames  103  are also removed and conveyed. Then, the comprehensive plant cultivation device  100  can be reconstructed at a new installation place. 
     Accordingly, a construction period required for manufacturing the comprehensive plant cultivation device  100  and a reconstruction period for reconstructing the comprehensive plant cultivation device  100  are short. For this reason, the comprehensive plant cultivation device  100  is installed in an unused factory or the like, and plants can be produced only for one season, for example. 
     It is possible to consider a business model which effectively makes use of an unused land by leasing the comprehensive plant cultivation device  100 . 
     In this embodiment, the respective seedling growing units  2  are placed on the shelf-like holding members  108  in a state where the end portions of the respective seedling growing units  2  are made to face each other, and the end portions of the seedling growing units  2  are connected with each other by the connecting member  55  which is a member separate from the seedling growing units  2 . Accordingly, when the connecting member  55  is removed, the engagement between the respective seedling growing units  2  is released so that the seedling growing unit  2  can be taken out individually. Accordingly, when the seedling growing unit  2  becomes defective, the defective seedling growing unit  2  can be removed for repairing, or can be exchanged with a new seedling growing unit  2 . That is, in the unit plant cultivation device  1 , although the continuous cylindrical space  60  is formed by three or more seedling growing units  2 , the seedling growing unit  2  disposed in the intermediate portion can be individually mounted or removed. 
     In the embodiment described above, the conveyance device  15  is driven by a motor. However, a power for driving the conveyance device  15  is not limited to the motor, and a member which utilizes a pneumatic pressure or a hydraulic pressure may be used. 
     Further, a handle is inserted into the conveyance device  15 , and the conveyance device  15  may be driven by rotating the handle. 
     As in the case of a seedling growing unit  150  shown in  FIG. 15  and  FIG. 16 , a conveyance device  154  may have a drive source thereinside. 
     The conveyance device  154  shown in  FIG. 15  and  FIG. 16  includes two elongated loop bodies  152  and a drive mechanism which drives the two elongated loop bodies  152 . 
     The elongated loop body  152  is formed of a belt or a chain. The elongated loop body  152  includes the plurality of moving-side engaging projecting portions  21 . 
     Each elongated loop body  152  extends between and is wound around a drive side rotary body  153  and a follower side rotary body  155 . The drive side rotary body  153  and the follower side rotary body  155  are formed of a pulley or a sprocket. 
     The two elongated loop bodies  152  are disposed parallel to each other with a fixed distance therebetween. A drive shaft  156  is interposed between two drive side rotary bodies  153 , and an interlocking shaft (not shown in the drawing) is interposed between two follower side rotary bodies  155 . 
     A motor not shown in the drawing is engaged with the drive shaft  156  so that the drive shaft  156  can be rotated in both forward and reverse directions. Accordingly, the two elongated loop bodies  152  can be rotated in both forward and reverse directions. 
     In the embodiment shown in  FIG. 15  and  FIG. 16 , the motor is incorporated in each case  5 . However, power may be transmitted between the seedling growing units  150  which are disposed adjacently to each other. 
     For example, as shown in  FIG. 17  and  FIG. 18 , double rotary bodies  160   a ,  160   b  are used. An elongated loop body  152  is made to extend between and be wound around the double rotary bodies  160   a ,  160   b . The double rotary body  160   a  of the seedling growing unit  150  and the double rotary body  160   b  of another seedling growing unit  150  are connected to each other by a power transmission member  161  formed of a belt, a chain or the like. 
     The embodiment shown in  FIG. 17  and  FIG. 18  has the configuration which includes the power transmission member  161  for transmitting power between moving mechanisms incorporated in the cases  5  disposed adjacently to each other. 
     In the embodiment described above, all series of operations from carrying in the seedling growing unit  2  to carrying out the seedling growing unit  2  are automatically controlled. However, some steps or all steps may be performed manually. 
     The layout shown in  FIG. 2  is designed assuming that the comprehensive plant cultivation device  100  is installed in a vacant warehouse or the like disposed above the ground. However, a place where the comprehensive plant cultivation device  100  is installed can be desirably determined. For example, the comprehensive plant cultivation device  100  may be installed in an underground tunnel, or an underground shopping area which is no longer used. 
     In this case, a layout shown in  FIG. 19  is used. The group of young seedling unit plant cultivation devices  105 , the tray exchange device  102 , the group of grown seedling unit plant cultivation devices  106 , the tray carrying-out device  112  and the tray conveyer  140  are installed under the ground. 
     The carrying-in port  135  of the tray carrying-in device  101  is disposed above the ground. 
     In the layout shown in  FIG. 19 , seedlings are planted to the cultivation tray  38  above the around. The cultivation tray  38  is lowered to an area under the ground by the tray carrying-in device  101 . The cultivation tray  38  is carried in the unit plant cultivation device  1 , and the seedlings are grown. 
     After the seedlings are grown, the cultivation tray  38  is discharged by the tray carrying-out device  112 . The cultivation tray  38  is placed on the tray conveyer  140  so as to move to the tray carrying-in device  101  side. Then, the cultivation tray  38  is placed on the tray carrying-in device  101 , and is carried out to an area above the ground. 
     In the above-mentioned embodiment, the group of young seedling unit plant cultivation devices  105  and the group of grown seedling unit plant cultivation devices  106  are arranged in a straight-line shape. However, a layout having bent portions such as a layout shown in  FIG. 20  may be adopted. 
     That is, a device which can change the advancing direction of the cultivation tray  38  is used as the tray exchange device  102 , and the cultivation tray  38  is carried in the unit plant cultivation device  1  on the downstream side by changing the advancing direction of the cultivation tray  38 . 
     In the embodiment described above, the plant cultivation device (plant cultivation system)  100  is formed of three kinds of members consisting of the young seedling unit plant cultivation device  1   a  and the grown seedling growing unit  2   b . However, the plant cultivation device  100  may be formed of four or more kinds of unit plant cultivation devices  1 . 
     That is, a plurality of unit plant cultivation devices each having a different environment in the cylindrical space  60 , including a height structure or other structures, the temperature setting, the humidity settings, illumination, a kind of culture solution and the like may be prepared, and a tray exchange device which transfers a cultivation tray from one unit plant cultivation device to another unit plant cultivation device may be provided. 
     In the embodiment described above, the connecting member  55  has a band shape. However, the connecting member  55  may be formed of a molded product as shown in  FIG. 21 . A connecting member  170  has a cross-sectional shape similar to a cross-sectional shape of the case  5 , and includes an arcuate roof portion  176  and side surface portions  177 ,  178  each having a vertical wall shape. The connecting member  170  does not include a bottom surface portion. 
     In the above-mentioned embodiment, in installing the seedling growing unit  2  to the unit installation space, a method is adopted where the seedling growing unit  2  is suspended by the fork member  142 , and the seedling growing unit  2  is transferred from the fork member  142  to the holding member  108 . However, the present invention is not limited to such a method. For example, the seedling growing unit  2  may be placed on an end portion of the holding member  108  in some way, and the seedling growing unit  2  may be installed to the unit installation space by making the seedling growing unit  2  laterally slide. 
     That is, the seedling growing unit  2  may be installed to the unit installation space by sliding the case  5  on the bottom support portion  110  to move the case  5  in the direction intersecting with the axis direction of the cylindrical space  60 . 
     In the above-mentioned embodiment, an air pressure in the cylindrical space  60  is held at a positive pressure. However, a pressure in the cylindrical space  60  may be set equal to an atmospheric pressure. 
     Another embodiment of the present invention is described. To facilitate the description, members having substantially the same function as the members in the previously described embodiment are given the same numbers, and the repeated description is omitted. 
       FIG. 22  shows a comprehensive plant cultivation device  200  according to another embodiment of the present invention. 
     In the comprehensive plant cultivation device  200 , independent two systems consisting of comprehensive plant cultivation devices  201   a ,  201   b  are disposed so as to face each other with a passage interposed therebetween. 
     The two systems consisting of the comprehensive plant cultivation devices  201   a ,  201   b  have the same structure and the same function. 
     Each comprehensive plant cultivation device  200  is formed of: five unit plant cultivation devices  1 ; an introducing/discharging-side lifting and lowering device  202 ; a returning lifting and lowering device  203 ; a tray conveyer  140 ; an air conditioning device  205 , and a culture solution supply device  206 . 
     In the comprehensive plant cultivation device  200 , a cultivation tray  90  as shown in  FIG. 29  and  FIG. 30  is used. 
     A seedling growing unit  3  forming the unit plant cultivation device  1  is as shown in  FIG. 24  and  FIG. 25 . That is, the seedling growing unit  3  includes a case  5  substantially equal to the case  5  in the previously described embodiment. Tray mounting bases  61 , linearly moving members  62 , illumination units  243  ( FIG. 25 ), and a water supply/discharge facility  63  are disposed inside the case  5 . 
     Further, in the seedling growing unit  3 , an air supply passage forming member  65  is incorporated in the case  5 . 
     The seedling growing unit  3  includes the case  5  which has both ends thereof opened and can cover a peripheral surface of the seedling growing unit  3 . 
     In the same manner as the previously described embodiment, the case  5  has an arcuate roof portion  6 . The roof portion  6  is made of a material such as stainless steel which has rust resistance and a favorable thermal conductivity. 
     As shown in  FIG. 25 , an outer peripheral surface of the roof portion  6  is covered by a moisturizing member  240 . The moisturizing member  240  is formed of a cloth such as a non-woven fabric, a mat or the like. The moisturizing member  240  forms a thin water layer on the outer peripheral surface of the roof portion  6 . 
     Also in this embodiment, a pipe  36  is mounted on a ridge portion of the roof portion  6  so that the roof portion  6  can be cooled by discharging water from the pipe  36 . Particularly in this embodiment, the moisturizing member  240  is disposed on the outer peripheral surface of the roof portion  6  so that the roof portion  6  is always brought into a wet state and hence, the moisturizing member  240  cools the roof portion  6  by depriving the roof portion  6  of vaporization heat. 
     In this embodiment, as shown in  FIG. 25 , an illumination board  241  is directly mounted on a metal plate forming the roof portion  6 . The illumination board  241  is a member where LEDs  243  are mounted on a thin resin board as light emitting elements. 
     Accordingly, heat generated by the LEDs  243  is directly transmitted to the metal plate forming the roof portion  6 , and is radiated to the outside. 
     In this embodiment, the LEDs  243  are controlled so as to flicker at a fine time interval. That is, the LEDs  243  flicker at intervals at which an operator recognizes with the naked eye that the LEDs  243  continuously emit light. 
     In this embodiment, a reflector  242  is mounted on an inner surface of the roof portion  6 . The reflector  242  has an arcuate shape which conforms to an arcuate shape of the inner surface of the roof portion  6  so that the reflector  242  covers the whole inner surface of the roof portion  6 . However, holes  245  are formed in the reflector  242  at portions where the LEDs  243  are present so that the cultivation tray  90  is irradiated with light of the LEDs  243  through the holes  245 . 
     In this embodiment, a transparent resin  246  is further formed on an outer side (cultivation tray  90  side) of the reflector  242 . The transparent resin  246  covers also the portions of the reflector  242  where the holes  245  are formed thus preventing invasion of water to the LED  243  side. 
     In this embodiment, the light emitting elements (LEDs  243 ) mounted on the inner surface of the roof portion  6  are not uniformly distributed. 
     To be more specific, a density of arrangement of the LEDs  243  in the vicinity of a peak of the ceiling surface is lower than a density of arrangement of the LEDs  243  in outskirt regions of the ceiling surface. 
     That is, in this embodiment, the illumination unit is disposed inside the case  5  which is bent in an arcuate shape. In this embodiment, as in the case of a region A shown in  FIG. 25C , the LEDs  243  in the vicinity of the peak of the ceiling surface radiate light toward an area directly below the LEDs  243 . Accordingly, the LEDs  243  in the vicinity of the peak of the ceiling surface radiate light to a center region of the cultivation tray  90 . 
     On the other hand, as in the case of regions B shown in  FIG. 25C , the LEDs  243  mounted on outskirt portions of the ceiling surface radiate light in the oblique direction. Accordingly, the LEDs  243  mounted on the outskirt portions of the ceiling surface radiate light to regions each ranging from an edge to the center region of the cultivation tray  90 . 
     Accordingly, when the light emitting elements are uniformly distributed on the inner surface of the roof portion  6 , an amount of light is large at the center region of the cultivation tray  90  compared to side portions of the cultivation tray  90 . In view of the above, in this embodiment, the number of LEDs  243  per unit area in the vicinity of the peak of the ceiling surface is reduced. 
     In the same manner as the previously described embodiment, the tray mounting base  61  is a member which can slidably move the cultivation trays  90  in a state where the cultivation trays  90  are placed on the tray mounting base  61 . As a configuration particular to this embodiment, a large number of short rollers  66  are mounted on the placing portions  14 . 
     In the same manner as the previously described embodiment, fixing-side engaging projecting portions  67  are formed on each placing portion  14 . Each fixing-side engaging projecting portion  67  is made of spring steel as a whole. One end of each fixing-side engaging projecting portion  67  is fixed to the placing portion  14  of the tray mounting base  61 , and the other end side of each fixing-side engaging projecting portion  67  projects outward from the placing portion  14 . The fixing-side engaging projecting portion  67  takes an inclined posture in a state where the other end side of the fixing-side engaging projecting portion  67  projects from the placing portion  14  of the tray mounting base  61 . When the fixing-side engaging projecting portion  67  receives an external force in a vertical direction, the fixing-side engaging projecting portion  67  sinks into the inside of the placing portion  14 , while when the external force is removed, the other end side of the fixed-side engaging projecting portion  67  projects outward from the placing portion  14  again. 
     In this embodiment, the linearly moving member (pressing member)  62  is an elongated body having an angular rod shape. The linearly moving member  62  is a member which corresponds to the pressing member connecting body  20  in the previously described embodiment, and the linearly moving member  62  is arranged in two rows. It is also safe to say that the linearly moving member  62  is a pressing member having a long length. 
     A moving-side engaging projecting portion (tray facing engaging portion)  68  is mounted on the linearly moving member  62 . The moving-side engaging projecting portion  68  has substantially the same structure and function as the above-mentioned fixing-side engaging projecting portion  67 . 
     The respective seedling growing units  3  are arranged in series, and the linearly moving members  62  of the seedling growing units  3  disposed adjacently to each other in the longitudinal direction are connected to each other by a joint fitting not shown in the drawing. 
     In the seedling growing unit  3  disposed on the most downstream side, a conveyance-unit-side engaging portion  70  as shown in  FIGS. 24, 34  is formed at an end portion of the linearly moving member  62 . The conveyance-unit-side engaging portion  70  is a member which has two side walls  72   a ,  72   b  and a front wall  71 , and also has a quadrangular opening  73  penetrating the conveyance-unit-side engaging portion  70  in the vertical direction. Further, a slit  74  extending in the vertical direction is formed in the front wall  71 . Accordingly, an opening extending in the vertical direction is disposed at a distal end of the conveyance-unit-side engaging portion  70 , and a space (opening  73 ) surrounded by the side walls  72   a ,  72   b  and the front wall  71  is disposed on the depth side of the opening. 
     The water supply/discharge facility  63  is formed of: a supply-side pipe  31  for supplying a culture solution to the cultivation trays  90 ; and a collecting-side pipe  32  for collecting a culture solution overflown from the cultivation trays. 
     The supply-side pipe  31  is formed of: one main pipe  33 ; and a plurality of branch pipes  35  branched from the main pipe  33 . 
     The branch pipe  35  is formed of a tube made of a resin or rubber. A throttle member  76  which adjusts an effective degree of opening of the branch pipe  35  by pressing a portion of the tube into a flat shape is mounted on each branch pipe  35 . In this embodiment, a supply amount of a culture solution can be adjusted by increasing or decreasing the effective degree of opening of the branch pipe  35  by the throttle member  76 . 
     In this embodiment, a small-sized pump  77  is installed outside each case  5 . A discharge side of the small-sized pump  77  is connected to the main pipe  33  of the supply-side pipe  31 . it is desirable that a motor for driving the small-sized pump  77  be a motor such as a DC motor where a rotational speed can be desirably changed. That is, it is desirable that the motor for driving the small-sized pump  77  be a motor where a supply amount of a culture solution can be adjusted by controlling a rotational speed of the small-sized pump  77 . 
     The collecting-side pipe  32  includes a culture solution collecting trough  46 . In the water supply/discharge facility  63  in this embodiment, the culture solution collecting trough  46  and the supply-side pipe  31  are disposed on the same side, at a position close to a side surface portion of the case  5  as shown in  FIG. 24  and  FIG. 25 . To be more specific, the culture solution collecting trough  46  and the supply-side pipe  31  are disposed on the passage side. 
     As described previously, in the comprehensive plant cultivation device  200 , the independent two systems consisting of the comprehensive plant cultivation devices  201   a ,  201   b  are disposed so as to face each other with the passage interposed therebetween. Accordingly, the culture solution collecting trough  46  and the supply-side pipe  31  of the seedling growing unit  3  belonging to the comprehensive plant cultivation device  201   a  and the culture solution collecting trough  46  and the supply-side pipe  31  of the seedling growing unit  3  belonging to the comprehensive plant cultivation device  201   b  have a mirror-image positional relationship. That is, left and right positions of the culture solution collecting trough  46  and the supply-side pipe  31  are converted between the seedling growing unit  3  belonging to the comprehensive plant cultivation device  201   a  and the seedling growing unit  3  belonging to the comprehensive plant cultivation device  201   b.    
     In the seedling growing unit  3  adopted in this embodiment, the air supply passage forming member  65  is incorporated in the case  5 . The air supply passage forming member  65  is formed of a main duct  80  made of a resin; a large number of air volume adjusting units  81  disposed on a periphery of the main duct  80 ; and a small-sized blower  85  incorporated in the main duct  80 . 
     As shown in  FIG. 27 , a large number of air supply ports  84  are formed in the main duct  80  of the air supply passage forming member  65 . Each air supply port  84  is formed of a circular opening. 
     Each air volume adjusting unit  81  is a unit where a resin duct having a diameter slightly larger than a diameter of the main duct  80  is cut with a short length, and a slit  82  extending in the axis direction is formed on the air volume adjusting unit  81 . A cross-sectional shape of the air volume adjusting unit  81  is a “C” shape. 
     Each air volume adjusting unit  81  is mounted on the main duct  80  at the position of the air supply port  84 . That is, the air volume adjusting unit  81  is mounted on the main duct  80  so as to surround the periphery of the main duct  80 . 
     The air volume adjusting unit  81  is rotatable with respect to the main duct  80  so that the air volume adjusting unit  81  can adjust a degree of opening of the air supply port  84 . That is, as shown in  FIG. 28A , by positioning the slit  82  at the position of the air supply port  84 , a substantial opening area of the air supply port  84  can be set to 100 percent. As shown in  FIG. 28C , by rotating the slit  82  to a side opposite to the air supply port  84 , the air supply port  84  can be closed. As shown in  FIG. 28B , by making the slit  82  partially aligned with the air supply port  84 , the substantial opening area of the air supply port  84  can be throttled. 
     A large duct  83  having a large inner diameter is connected to the main duct  80  in series, and the small-sized blower  85  is incorporated in the large duct  83 . A motor  86  for driving the small-sized blower  85  is a motor such as a DC motor which can desirably change a rotational speed. The small-sized blower  85  is formed of an axial-flow fan. 
     The seedling growing units  3  are linearly connected. In connecting the seedling growing units  3  with each other, the main ducts  80  disposed adjacently to each other are also connected with each other. Accordingly, in the cylindrical space  60  of the unit plant cultivation device  1 , the main ducts  80  of the air supply passage forming member  65  communicate with each other. 
     Next, the cultivation tray  90  is described. In the same manner as the previously described embodiment, as shown in  FIG. 29 , the cultivation tray  90  is formed of a container portion  40  having a quadrangular shape as viewed in a plan view, and a seedling holding plate  41 . 
     The container portion  40  is a tray having a structure which prevents leakage of water and has an open-ended upper surface. The container portion  40  is formed so as to have a slightly larger area in the vicinity of the opening portion. 
     In this embodiment, overflow pipe portions  91   a ,  91   b  are formed in the container portion  40 . The overflow pipe portions  91   a ,  91   b  are formed at positions of the container portion  40  close to one side of the container portion  40 . 
     That is, a planar shape of the container portion  40  is a rectangular shape, and has long sides  92   a ,  92   b  disposed on sides opposite to each other and short sides  93   a ,  93   b  disposed on sides opposite to each other. A region surrounded by the long sides  92   a ,  92   b  and the short sides  93   a ,  93   b  forms a solution storing portion. 
     The overflow pipe portions  91   a ,  91   b  are formed on a bottom of the container portion  40  at the positions close to the short side  93   a.    
     Each of the overflow pipe portions  91   a ,  91   b  is a tubular portion penetrating the container portion  40  in the vertical direction, and the distal end side of the overflow pipe portion is disposed at a raised position from the bottom of the container portion  40 . The overflow pipe portions  91   a ,  91   b  function as discharge ports for discharging a surplus culture solution. 
     In this embodiment, flow passage forming walls  95   a ,  95   b ,  95   c  are formed on the bottom of the container portion  40 . 
     All of the flow passage forming walls  95   a ,  95   b ,  95   c  extend parallel to the long sides  92   a ,  92   b  of the container portion  40 , and are alternately brought into contact with the short sides  93   a ,  93   b  of the container portion  40 . 
     That is, the flow passage forming wall  95   a  extends parallel to the long side  92   a  using the short side  93   a  on the side close to the overflow pipe portions  91   a ,  91   b  as a start end, and reaches an area in the vicinity of the other short side  93   b . A distal end of the flow passage forming wall  95   a  does not reach the other short side  93   b  so that a gap  96   a  is formed between the distal end of the flow passage forming wall  95   a  and the other short side  93   b  of the container portion  40 . 
     The flow passage forming wall  95   b  extends parallel to the long side  92   a  using the other short side  93   b  as a start end, and reaches an area in the vicinity of the short side  93   a  on the side close to the overflow pipe portions  91   a ,  91   b . A distal end of the flow passage forming wall  95   b  does not reach the short side  93   a  so that a gap  96   b  is formed between the distal end of the flow passage forming wall  95   b  and the short side  93   a  of the container portion  40 . 
     The flow passage forming wall  95   c  extends parallel to the long side  92   a  using the short side  93   a  on the side close to the overflow pipe portions  91   a ,  91   b  as a start end, and reaches an area in the vicinity of the other short side  93   b . A distal end of the flow passage forming wall  95   c  does not reach the other short side  93   b  so that a gap  96   c  is formed between the distal end of the flow passage forming wall  95   e  and the other short side  93   b  of the container portion  40 . 
     As for a region ranging from the center of the bottom of the container portion  40  to the overflow pipe portion  91   a , the gap  96   b  at a center portion is connected with an outgoing flow passage  97   a  formed by the flow passage forming wall  95   b  and the flow passage forming wall  95   a . The outgoing flow passage  97   a  is also connected with the gap  96   a . Further, the gap  96   a  is connected with a return flow passage  97   b  formed by the flow passage forming wall  95   a  and the long side  92   a  of the container portion  40 , and reaches the overflow pipe portion  91   a.    
     That is, the gap  96   b  at the center portion and the overflow pipe portion  91   a  are connected with each other through a series of flow passages formed of the outgoing flow passage  97   a , the gap  96   a  and the return flow passage  97   b.    
     The same goes for a region ranging from the center of the bottom of the container portion  40  to the overflow pipe portion  91   b . The gap  96   b  at the center portion is connected with an outgoing flow passage  97   c  formed by the flow passage forming wall  95   b  and the flow passage forming wall  95   c . The outgoing flow passage  97   c  is also connected with the gap  96   c . Further, the gap  96   c  is connected with a return flow passage  97   d  formed by the flow passage forming wall  95   c  and the long side  92   b  of the container portion  40 , and reaches the overflow pipe portion  91   b.    
     That is, the gap  96   b  at the center portion and the overflow pipe portion  91   b  are connected with each other through a series of flow passages formed of the outgoing flow passage  97   c , the gap  96   c  and the return flow passage  97   d.    
     In this embodiment, a culture solution is dripped to the gap  96   b  at the center portion. In this embodiment, an area from a portion to which a culture solution is supplied to each of the overflow pipe portion  91   a ,  91   b  is connected through the flow passages connected in series. 
     In this embodiment, the flow passages from the portion to which a culture solution is supplied to the overflow pipe portions  91   a ,  91   b  are flow passages which use straight lines formed basically by the flow passage forming walls  95   a, b, c  extending in a straight line-shape. However, the flow passages from the portion to which a culture solution is supplied to the overflow pipe portions  91   a ,  91   b  may be curved flow passages by extending the flow passage forming walls in a curved shape. 
     Next, an introducing/discharging-side lifting and lowering device  202  is described. 
     The introducing/discharging-side lifting and lowering device  202  includes a lifting and lowering table  125  which is suspended by a chain, a wire or the like and is lifted and lowered. A conveyor device  180 , a conveyance unit drive device  181 , a cultivation tray inclining unit  182 , and a trough  183  are mounted on the lifting and lowering table. 
     The conveyor device  180  is formed of a pair of belt traveling members  185   a ,  185   b  disposed in a spaced apart manner with a fixed distance therebetween. 
     The belt traveling members  185   a ,  185   b  use pulley members  193  disposed on both end portions of a motor-incorporating roller  195  as drive sources. Each of the belt traveling members  185   a ,  185   b  includes a plurality of follower pulleys  188   a, b, c, d  with which a belt  186  is engaged and which change traveling of the belt  186 , and a plurality of short rollers  190  which support a weight of a cultivation tray. 
     That is, the follower pulleys and the short rollers are supported by a pulley support plate  191  in a cantilever manner. The belt  186  extends between and is wound around the pulley member  193  and the follower pulleys  188   a, b, c, d.    
     The conveyor device  180  is formed such that two belts  186  disposed parallel to each other are made to travel by driving the motor-incorporating rollers  195 . 
     The conveyance unit drive device  181  includes a pair of longitudinal-direction drive devices disposed in a spaced apart manner with a fixed distance therebetween. 
     In the longitudinal-direction drive device, a belt  215  extends and is wound around one of drive side pulley members  211  disposed on both ends of the motor-incorporating roller  210  and one of follower side pulley members  213  disposed on both ends of an idling roller  212 . The belt  215  is formed of a toothed belt, and the drive side pulley member  211  and the follower side pulley member  213  are respectively formed of a toothed pulley. 
     In the conveyance unit drive device  181 , a drive-side engaging member  216  is mounted on the belt  215  of the above-mentioned longitudinal-direction drive device. The drive-side engaging member  216  is a member having an approximately T shape, and is formed of an elongated extension rod portion  217  and a drive side engaging portion  218  disposed on a distal end of the extension rod portion  217  and extending in the direction intersecting with the extension rod portion  217 . 
     In this embodiment, the extension rod portion  217  is formed of a strip-shaped steel material. 
     The extension rod portion  217  is used such that the width direction of the strip-shaped steel material takes a vertical posture, and the longitudinal direction of the strip-shaped steel material is directed in the horizontal direction. The drive side engaging portion  218  is integrally formed with the distal end of the extension rod portion  217 . 
     In this embodiment, the conveyance unit drive device  181  is formed such that the drive-side engaging member  216  is fixed to the belt  215  of the longitudinal-direction drive device, and the drive-side engaging member  216  is linearly moved in the longitudinal direction by driving the motor-incorporating roller  210 . 
     The drive-side engaging member  216  is engaged with a guide not shown in the drawing so that the drive-side engaging member  216  is guided so as to move linearly. 
     The conveyance unit drive device  181  is disposed on the lifting and lowering table  125  so that the conveyance unit drive device  181  is moved also in the vertical direction by lifting and lowering the lifting and lowering table  125 . 
     Next, the cultivation tray inclining unit  182  is described. The cultivation tray inclining unit  182  is formed of one rod which is moved in the longitudinal direction. 
     More specifically, the cultivation tray inclining unit  182  is formed of: an inclining engaging member  220 ; a drive mechanism  221  which linearly moves the inclining engaging member; and a guide member (not shown in the drawing) which guides the inclining engaging member  220  such that the inclining engaging member  220  is moved in the linear direction. 
     The inclining engaging member  220  is an elongated member, and a rack  222  is formed on a lower surface of the inclining engaging member  220 . A pinion  223  is engaged with the rack  222 . The pinion  223  is driven by a geared motor  225 . 
     Accordingly, when the pinion  223  is rotated by driving the geared motor  225 , the rack  222  which is engaged with the pinion  223  is linearly moved so that the inclining engaging member  220  is linearly moved in the longitudinal direction. 
     The rack  222  is disposed at the position on the lifting and lowering table  125  close to the unit plant cultivation device  1 . Accordingly, when the inclining engaging member  220  is moved to the unit plant cultivation device  1  side by driving the geared motor  225 , the inclining engaging member  220  enters the seedling growing unit  3  side of the unit plant cultivation device  1 . 
     The cultivation tray inclining unit  182  is disposed on the lifting and lowering table  125  so that the cultivation tray inclining unit  182  is moved also in the vertical direction by lifting and lowering the lifting and lowering table  125 . 
     Next, a positional relationship between respective members on the lifting and lowering table  125  is described. 
     As described previously, the conveyor device  180 , the conveyance unit drive device  181 , the cultivation tray inclining unit  182 , and the trough  183  are installed on the lifting and lowering table  125 . 
     The respective members take the positional relationship shown in  FIG. 31 , and the trough  183  is disposed on one side of the lifting and lowering table  125  in the width direction. In  FIG. 31 , the trough  183  is disposed on a left end of the lifting and lowering table  125 , and the trough  183  extends linearly toward the unit plant cultivation device  1  side. 
     On the other hand, the cultivation tray inclining unit  182  is installed on the other side of the lifting and lowering table  125  in the width direction. That is, in this embodiment, the trough  183  and the cultivation tray inclining unit  182  are disposed on both sides of the lifting and lowering table  125 . 
     The conveyor device  180  and the conveyance unit drive device  181  are disposed in a region between the trough  183  and the cultivation tray inclining unit  182 . 
     To be more specific, the conveyor device  180  is disposed inside the region between the trough  183  and the cultivation tray inclining unit  182 , and the conveyance unit drive device  181  is disposed further inside the conveyor device  180 . 
     That is, as described previously, the conveyor device  180  is formed of the pair of belt traveling members  185   a ,  185   b  disposed in a spaced apart manner with a fixed distance therebetween. One of the belt traveling members  185   a ,  185   b  is disposed on the side of the trough  183  and the other of the belt traveling members  185   a ,  185   b  is disposed on the side of the cultivation tray inclining unit  182 . 
     The conveyance unit drive device  181  is disposed in the region surrounded by the pair of belt traveling members  185   a ,  185   b . That is, the conveyance unit drive device  181  includes the pair of longitudinal-direction drive devices, and one longitudinal-direction drive device is disposed on the side of the belt traveling member  185   a  and the other longitudinal-direction drive device is disposed on the side of the belt traveling member  185   b.    
     The returning lifting and lowering device  203  is a device which does not include the cultivation tray inclining unit  182 , the conveyance unit drive device  181  and the trough  183 , but includes the conveyor device  180  disposed on the lifting and lowering table  127 . 
     The tray conveyer  140  is formed of a roller conveyer. However, the tray conveyer  140  may be formed of a belt conveyer. 
     The tray conveyer  140  is a conveyer which is connected with the conveyor device  180  of the introducing/discharging-side lifting and lowering device  202  in one row when the lifting and lowering table  125  of the introducing/discharging-side lifting and lowering device  202  is lifted to a top stage. Accordingly, the cultivation tray  90  discharged from the introducing/discharging-side lifting and lowering device  202  is placed on the tray conveyer  140 , and the tray conveyer  140  can move the cultivation tray  90  to the returning lifting and lowering device  203  side. 
     When the lifting and lowering table  127  of the returning lifting and lowering device  203  is lifted to the top stage, the conveyor device  180  of the returning lifting and lowering device  203  and the tray conveyer  140  are connected with each other in one row. Accordingly, the cultivation tray  90  can be transferred from the tray conveyer  140  to the returning lifting and lowering device  203 . 
     In the comprehensive plant cultivation device  200  of this embodiment, both the introducing/discharging-side lifting and lowering device  202  and the tray conveyer  140  are surrounded by outer wall members having gas-tightness so that gas-tightness is ensured between the inside and the outside of the comprehensive plant cultivation device  200 . The introducing/discharging-side lifting and lowering device  202  and the tray conveyer  140  communicate with each other. Accordingly, a series of air flow passages is formed by the introducing/discharging-side lifting and lowering device  202  and the tray conveyer  140 . 
     A terminal end portion of the tray conveyer  140  is connected to the suction side of the air conditioning device  205  by way of a duct  226 . 
     The discharge side of the air conditioning device  205  is connected to the main duct  80  of the air supply passage forming member  65  in the cylindrical space  60  of each unit plant cultivation device  1  by way of a duct or the like. 
     Next, a function of the comprehensive plant cultivation device  200  is described. As described previously, in the comprehensive plant cultivation device  200 , independent two systems consisting of the comprehensive plant cultivation devices  201   a ,  201   b  are disposed so as to face each other with the passage interposed therebetween. Accordingly, both comprehensive plant cultivation devices  201   a ,  201   b  are collectively referred to as the comprehensive plant cultivation device  200 . 
     First, a flow of the cultivation tray  90  in the comprehensive plant cultivation device  200  is described. In the comprehensive plant cultivation device  200  of this embodiment, the cultivation tray  90  is conveyed as indicated by an arrow in  FIG. 22A . 
     That is, the cultivation tray  90  is carried in the introducing/discharging-side lifting and lowering device  202 . To be more specific, the lifting and lowering table  125  of the introducing/discharging-side lifting and lowering device  202  is lowered to a lowermost portion. Then, the cultivation tray  90  is conveyed by a conveyance device not shown in the drawing, and the cultivation tray  90  is placed on the lifting and lowering table  125 . At this time of operation, the cultivation tray  90  is pulled to the lifting and lowering table  125  side by driving the conveyor device  180 . 
     Subsequently, the lifting and lowering table  125  of the introducing/discharging-side lifting and lowering device  202  is lifted to the top stage, and the cultivation tray  90  is transferred from the lifting and lowering table  125  to the tray conveyer  140 . 
     Then, the cultivation tray  90  is transferred to the lifting and lowering table  127  of the returning lifting and lowering device  203  by driving the tray conveyer  140 . 
     Thereafter, the lifting and lowering table  127  of the returning lifting and lowering device  203  is lowered to a desired stage, and the cultivation tray  90  is carried in the unit plant cultivation device  1  at the desired stage. 
     Subsequently, the cultivation tray  90  is moved to the downstream side while allowing plants to grow in the unit plant cultivation device  1 . When the cultivation tray  90  reaches a terminal end of the unit plant cultivation device  1 , the cultivation tray  90  is moved to the lifting and lowering table  125  of the introducing/discharging-side lifting and lowering device  202 . Then, the lifting and lowering table  125  is lowered to a lowermost stage, and the cultivation tray  90  is discharged from the lifting and lowering table  125  by driving the conveyor device  180 . 
     Next, functions which feature the comprehensive plant cultivation device  200  of this embodiment is described. 
     In the comprehensive plant cultivation device  200  of this embodiment, in taking out the cultivation tray  90 , which reaches the terminal end of the unit plant cultivation device  1 , to the lifting and lowering table  125  of the introducing/discharging-side lifting and lowering device  202 , the cultivation tray  90  is inclined toward the culture solution collecting trough  46  side in the seedling growing unit  3  disposed at the terminal end so as to drain a culture solution in the seedling growing unit  3 . 
     Hereinafter, the operation for draining a culture solution is described with reference to  FIG. 33 . 
     in introducing the cultivation tray  90 , which reaches the terminal end of the unit plant cultivation device  1 , to the lifting and lowering table  125  of the introducing/discharging-side lifting and lowering device  202 , the lifting and lowering table  125  is moved as shown in  FIG. 33A  so as to make a height of the lifting and lowering table  125  agree with a height of the corresponding unit plant cultivation device  1 . 
     In this embodiment, the inclining engaging member  220  is disposed on the lifting and lowering table  125 . However, the inclining engaging member  220  is pulled into the region of the lifting and lowering table  125  so that the inclining engaging member  220  is disposed at the position where the inclining engaging member  220  is not engaged with the cultivation tray  90 . Accordingly, even when the lifting and lowering table  125  is lifted and lowered, there is no possibility that the inclining engaging member  220  collides with the seedling growing unit  3  or the cultivation tray  90 . 
     The same goes for the conveyance unit drive device  181 . The drive-side engaging member  216  is pulled into the region of the lifting and lowering table  125 . Accordingly, even when the lifting and lowering table  125  is lifted and lowered, there is no possibility that the drive-side engaging member  216  collides with the seedling growing unit  3  or the cultivation tray  90 . 
     Subsequently, the pinion  223  is rotated by driving the geared motor  225  so that the rack  222  which is engaged with the pinion  223  is linearly moved. Accordingly, the inclining engaging member  220  is made to advance thus being inserted into the seedling growing unit  3  at the terminal end as shown in  FIG. 33B . 
     As shown in  FIG. 33B , the inclining engaging member  220  is moved to the lower side of the cultivation tray  90  on the side opposite to the culture solution collecting trough  46 . 
     As a result, the inclining engaging member  220  is moved from a position where the inclining engaging member  220  cannot be engaged with the cultivation tray  90  to the position where the inclining engaging member  220  can be engaged with the cultivation tray  90 . 
     With such a state, as shown in  FIG. 33C , the lifting and lowering table  125  is slightly lifted. As a result, the inclining engaging member  220  is lifted along with the lifting of the lifting and lowering table  125  so that only one side of the cultivation tray  90  is lifted. 
     Accordingly, the cultivation tray  90  is inclined toward the culture solution collecting trough  46  side so that a culture solution in the cultivation tray  90  is drained. 
     After the draining of the culture solution is finished, as shown in  FIG. 33D , the lifting and lowering table  125  is lowered, and the cultivation tray  90  is returned to an original posture. 
     Then, as shown in  FIG. 33E , the geared motor  225  is subsequently reversely rotated so as to rotate the pinion  223  so that the rack  222  which is engaged with the pinion  223  is linearly moved. Accordingly, the inclining engaging member  220  is made to retract thus being returned from the inside of the seedling growing unit  3  to the lifting and lowering table  125  side. 
     Subsequently, the cultivation tray  90  at the terminal end of the unit plant cultivation device  1  is pulled out from the seedling growing unit  3  to the lifting and lowering table  125  of the introducing/discharging-side lifting and lowering device  202 . 
     Hereinafter, the operation is described with reference to  FIG. 34 ,  FIG. 35  and  FIG. 36 . 
       FIG. 34A  shows a relationship between the lifting and lowering table  125 , the conveyance unit drive device  181 , and the seedling growing unit  3  at the terminal end immediately after the inclining engaging member  220  is returned from the inside of the seedling growing unit  3  to the lifting and lowering table  125  side. 
       FIG. 36A  shows a relationship between the drive-side engaging member  216  and the conveyance-unit-side engaging portion  70  of the seedling growing unit  3  at the terminal end immediately after the inclining engaging member  220  is returned from the inside of the seedling growing unit  3  to the lifting and lowering table  125  side. 
     In pulling out the cultivation tray  90  at the terminal end to the lifting and lowering table  125  side of the introducing/discharging-side lifting and lowering device  202 , the lifting and lowering table  125  is slightly lifted as shown in  FIG. 34B . 
     As a result, the drive-side engaging member  216  is lifted together with the lifting and lowering table  125  as shown in  FIG. 34B  and  FIG. 36B . 
     Subsequently, the drive-side engaging member  216  is made to advance. 
     To be more specific, the belt  215  is made to travel by driving the motor-incorporating roller  210  so as to make the drive-side engaging member  216  fixed to the belt  215  move to the unit plant cultivation device  1  side. 
     In this embodiment, the conveyance-unit-side engaging portion  70  is formed on the seedling growing unit  3  at the terminal end of the unit plant cultivation device  1 . However, the lifting and lowering table  125  is lifted in advance and hence, a height of the drive-side engaging member  216  is higher than the conveyance-unit-side engaging portion  70  on the seedling growing unit  3  side ( FIG. 36B ). 
     Accordingly, even when the drive-side engaging member  216  is moved to the unit plant cultivation device  1  side, there is no possibility that the drive-side engaging member  216  collides with the conveyance-unit-side engaging portion  70  ( FIG. 36C ). 
     As described above, as shown in  FIG. 34B  and  FIG. 36C , the drive side engaging portion  218  of the drive-side engaging member  216  is made to reach the position directly above the conveyance-unit-side engaging portion  70 . 
     Subsequently, the lifting and lowering table  125  is lowered. As a result, as shown in  FIG. 34C  and  FIG. 36D , a distal end portion of the drive-side engaging member  216  enters the quadrangular opening  73  which penetrates the conveyance-unit-side engaging portion  70  in the vertical direction from the upper side. The slit  74  extending in the vertical direction is formed in the front wall  71  of the conveyance-unit-side engaging portion  70 , and the extension rod portion  217  of the drive-side engaging member  216  passes through the slit  74 . 
     Subsequently, as shown in  FIG. 35D  and  FIG. 36E , the drive-side engaging member  216  is made to retract. In this embodiment, the distal end portion (drive side engaging portion  218 ) of the drive-side engaging member  216  enters the opening  73  of the conveyance-unit-side engaging portion  70  so that the drive side engaging portion  218  is engaged with the conveyance-unit-side engaging portion  70 . Accordingly, along with the retracting of the drive-side engaging member  216 , the linearly moving member  62  of the seedling growing unit  3  is linearly moved thus being pulled into the lifting and lowering table  125  side. 
     As a result, the cultivation tray  90  in the respective seedling growing unit  3  which is engaged with the moving-side engaging projecting portion (drive side engaging portion)  68  of the linearly moving member  62  is made to advance to the introducing/discharging-side lifting and lowering device  202  side and, as shown in  FIG. 35D , the cultivation tray  90  at the distal end is pulled into the lifting and lowering table  125  side of the introducing/discharging-side lifting and lowering device  202 . 
     Thereafter, as shown in  FIG. 35E , the drive-side engaging member  216  is made to advance to the seedling growing unit  3  side thus returning the linearly moving member  62  to the inside of the seedling growing unit  3 . 
     After these operations, the above-mentioned steps are performed in an opposite manner. To be more specific, the lifting and lowering table  125  is lifted so as to remove the distal end portion (drive side engaging portion  218 ) of the drive-side engaging member  216  from the opening  73  of the conveyance-unit-side engaging portion  70 . Further, the drive-side engaging member  216  is made to retract, and is returned to the lifting and lowering table  125  side. 
     In this embodiment, the linearly moving member  62  is provided to each of all seedling growing units  3  forming one unit plant cultivation device  1 , and all linearly moving members  62  are connected with each other in series by connecting fittings. Accordingly, by linearly moving the linearly moving member  62  of the seedling growing unit  3  at the terminal end of the unit plant cultivation device  1  by the conveyance unit drive device  181  on the lifting and lowering table  125  side, the linearly moving members  62  in all seedling growing units  3  are moved to the introducing/discharging-side lifting and lowering device  202  side. As a result, the cultivation trays  90  in all seedling growing units  3  are moved to the introducing/discharging-side lifting and lowering device  202  side. 
     Thereafter, the drive-side engaging member  216  is made to advance so as to return the linearly moving member  62  to the inside of the seedling growing unit  3 . In accordance with steps opposite to the above-mentioned steps, the lifting and lowering table  125  is lifted so as to lift the drive side engaging portion  218  of the drive-side engaging member  216  thus removing the drive side engaging portion  218  from the opening  73  of the conveyance-unit-side engaging portion  70 . 
     Thereafter, the drive-side engaging member  216  is made to retract, and is returned to the lifting and lowering table  125  side. 
     Next, the manner of operation of the respective parts when plants are grown in the unit plant cultivation device  1  is described. 
     In the comprehensive plant cultivation device  200  of this embodiment, wind can be generated in a desired area in the cylindrical space  60 . 
     That is, the comprehensive plant cultivation device  200  of this embodiment includes the air conditioning device  205 , and the discharge side of the air conditioning device  205  is connected to the main duct  80  of the air supply passage forming member  65  in the cylindrical space  60  of the respective unit plant cultivation device  1  by way of a duct or the like. 
     The air supply passage forming member  65  is disposed in the cylindrical space  60  in a penetrating manner in the axis direction, and the small-sized blower  85  is disposed in an intermediate portion of the air supply passage forming member  65 . To be more specific, one small-sized blower  85  is provided to each seedling growing unit  3  forming the unit plant cultivation device  1 . 
     A large number of air supply ports  84  are formed in the main duct  80 . That is, the large number of air supply ports  84  are disposed between the discharge side of the small-sized blower  85  of one seedling growing unit  3  and the suction side of the small-sized blower  85  of the next seedling growing unit  3 . 
     Accordingly, even when a pressure on the discharge side of the air conditioning device  205  is insufficient, the pressure is increased by the small-sized blower  85  disposed at the intermediate portion so that wind can be supplied to the inside of the cylindrical space  60  from the respective air supply ports  84 . 
     A degree of opening of each air supply port  84  can be changed from a fully closed state to a fully opened state and hence, wind can be supplied to a required place. 
     In this embodiment, the degree of opening of each air supply port  84  is adjusted manually. However, a method is also recommended where the degree of opening of each air supply port  84  is remote-controlled using a motor valve or the like. 
     A method is also recommended where a louver which is driven by a power is mounted on the air supply port  84 , and the air supply direction is regularly changed. 
     The control of a supply air volume can be performed based on information such as an electric current supplied to a motor, a rotational speed of the motor or the air supply direction. 
     A plurality of the air supply passage forming members  65  may be provided. For example, plural systems of the air supply passage forming members  65  are provided, and a temperature or humidity of air which flows through each air supply passage forming member  65  may be changed for the respective air supply passage forming members  65 . 
     A plurality of the air supply passage forming members  65  may be provided, and one or some air supply passage forming members  65  may be used for sucking out air. For example, if there is an area where a concentration of carbon dioxide is high, air in the region may be sucked out by the air supply passage forming member for sucking out air so as to replace the air. 
     A plurality of the small-sized blowers  85  are provided to the air supply passage forming member  65 , and the air supply ports  84  are disposed between two small-sized blowers  85  and hence, depending on an air supply force of the small-sized blower  85 , there may be a tendency for some air supply ports  84  to become a negative pressure. 
     For example, when an air supply volume of one small-sized blower  85  is small and a suction force of the next small-sized blower  85  is strong, the air supply ports  84  disposed between two small-sized blowers  85  tend to become a negative pressure thus sucking out air in the cylindrical space  60 . 
     Accordingly, wind may be generated or carbon dioxide or the like may be diffused by intentionally bringing the air supply ports  84  into a negative pressure thus sucking out air in the cylindrical space  60 . 
     The air supply passage forming member  65  may have an arbitrary cross-sectional shape. 
     Air discharged from the air supply ports  84  locally generates wind in the vicinity of the air supply ports  84 . That is, in this embodiment, an air supply unit which moves air in the cylindrical space by supplying air is provided. The air supply unit can have a different supply air volume for every area so that the air supply unit can locally generate wind. 
     In an area apart from an area disposed in the vicinity of the air supply ports  84 , a flow of air is slow and air is dispersed to the whole cylindrical space  60  so that a pressure in the cylindrical space  60  is increased. 
     In this embodiment, the cylindrical space  60  is opened to the introducing/discharging-side lifting and lowering device  202  and, further, the introducing/discharging-side lifting and lowering device  202  and the tray conveyer  140  communicate with each other thus forming a series of air flow passages. 
     A terminal end portion of the tray conveyer  140  is connected to the suction side of the air conditioning device  205  by way of the duct  226 . Accordingly, air discharged from the discharge side of the air conditioning device  205  enters the cylindrical space  60  from the air supply ports  84  of the air supply passage forming member  65  and, then, is returned to the air conditioning device  205  through the introducing/discharging-side lifting and lowering device  202  and the tray conveyer  140 . That is, air circulates a series of circulation paths including the air conditioning device  205 . 
     Next, the culture solution is described. 
     In this embodiment, the culture solution supply device  206  is disposed below the comprehensive plant cultivation device  200 . The culture solution supply device  206  includes a culture solution tank and a pump not shown in the drawing. 
     In this embodiment, a supply tank (not shown in the drawing) is disposed above the comprehensive plant cultivation device  200 , and the supply tank and the small-sized pumps  77  attached to the respective seedling growing units  3  are connected with each other. 
     A culture solution is supplied to the supply tank (not shown in the drawing) from the pump of the comprehensive plant cultivation device  200  so that a fixed level of the culture solution is always stored in the supply tank. 
     The culture solution is fed by gravity to the small-sized pump  77  from the supply tank, and the culture solution pressurized by the small-sized pump  77  is supplied to the main pipe  33  of the supply-side pipe  31 . Then, the culture solution is supplied to the respective cultivation trays  90  from the branch pipes  35 . 
     In this embodiment, the culture solution is supplied to an area between two overflow pipe portions  91   a ,  91   b  on the short side  93   a  side of each cultivation tray  90  and on the same side as the overflow pipe portions  91   a ,  91   b . That is, the culture solution is supplied to the gap  96   a.    
     In this embodiment, in the region ranging from the center of the bottom of the container portion  40  to the overflow pipe portion  91   a , one flow passage starting from the gap (the region to which the culture solution is dripped)  96   b  to the overflow pipe portion  91   a  is formed. 
     The same goes for the region ranging from the center of the bottom of the container portion  40  to the overflow pipe portion  91   b . One flow passage starting from the gap  96   b  (the region to which the culture solution is dripped) at the center portion to the overflow pipe portion  91   b  is formed in the region. 
     Accordingly, the culture solution supplied to the gap  96   b  flows to the overflow pipe portions  91   a ,  91   b  without causing stagnation, is collected by the culture solution collecting trough  46 , and is returned to the culture solution supply device  206  by way of pipes not shown in the drawing. 
     It is recommended to adopt a small-sized centrifugal pump as the small-sized pump  77 . However, a pump such as a gear pump where a discharge amount is proportional to a rotational speed may be used as the small-sized pump  77 . For example, when the gear pump is used, an amount of culture solution supplied to the respective cultivation trays  90  can be accurately controlled. Further, it is recommended to use a pump which incorporates a check valve as the small-sized pump  77 . The above-mentioned gear pump or the like originally has a reverse flow preventing function so that such a pump is also recommended. 
     Wind generated in the cylindrical space  60  and an amount of a culture solution supplied to the cultivation tray  90  which are described above may be remote-controlled or controlled by a program which is set in advance. 
     Further, it may be possible to adopt the configuration where the comprehensive plant cultivation device  200  is connected to the Internet, and wind and a culture solution are adjusted from a place remote from the comprehensive plant cultivation device  200 . 
     For example, it is desirable that a rotational speed of the small-sized blower  85 , a degree of opening of the air supply ports  84  and the like be remote-controllable. For example, it is desirable that the comprehensive plant cultivation device  200  be connected to the Internet or the like, and a supply air volume and the like be adjustable from a place remote from the comprehensive plant cultivation device  200 . When the supply air volume and the like are adjusted through the Internet, it is recommended to provide a camera which monitors the respective parts of the comprehensive plant cultivation device  200  and the cultivation trays  90  in the comprehensive plant cultivation device  200 . 
     It is also recommended that a change in supply air volume be programed in advance according to a kind of plants, a season, a place in the cylindrical space  60  or the like, and the supply air volume be changed in accordance with the program. For example, the degree of growth of plants is determined by a distance from the returning lifting and lowering device  203  of the cylindrical space  60 . Accordingly, the generation of wind is programed such that wind of a specific air volume is generated only for a specific time only in a specific area, and the supply air volume is changed in accordance with the program. 
     The same goes for the supply amount of a culture solution. It is desirable that the comprehensive plant cultivation device  200  be connected to the Internet or the like, and a rotational speed of the small-sized pump  77  and the like be adjustable from a place remote from the comprehensive plant cultivation device  200 . 
     It is also recommended that a supply amount of the culture solution be programed in advance according to a kind of plants, a season, a place in the cylindrical space  60  and the like, and a rotational speed of the small-sized pump  77  or the like be changed in accordance with the program. For example, a supply amount of the culture solution is programed such that a large amount of culture solution is supplied only for a specific time only in a specific area, and the rotational speed of the small-sized pump  77  is changed in accordance with the program. 
     In the embodiment described above, the conveyance unit drive device  181  which drives the conveyance unit is mounted on the introducing/discharging-side lifting and lowering device  202 . The lifting and lowering table  125  of the introducing/discharging-side lifting and lowering device  202  is stopped at a desired stage, and the drive side engaging portion  218  of the conveyance unit drive device  181  is engaged with the linearly moving member  62  on the seedling growing unit  3  side. Then, the linearly moving member  62  of the seedling growing unit  3  is linearly moved thus making the cultivation trays  90  in the all seedling growing units  3  advance. 
     With such a configuration, the linearly moving members  62  of the plurality of unit plant cultivation devices  1  can be operated by one conveyance unit drive device  181  so that only a small number of parts is required. 
     Further, a power portion is disposed outside the cylindrical space  60  and hence, maintenance can be easily performed. 
     In the above-mentioned embodiment, the configuration is adopted where engaging/disengaging between the drive side engaging portion  218  and the linearly moving member  62  on the seedling growing unit  3  side is performed by lifting and lowering the lifting and lowering table  125 . However, the present invention is not limited to such a configuration. It may be possible to adopt the configuration where a zipper or the like is provided to the drive side engaging portion  218 , and the engaging/disengaging between the drive side engaging portion  218  and the linearly moving member  62  is performed by operating the zipper. 
     In the embodiment described above, a culture solution is discharged by inclining whole the cultivation tray  90  immediately before the cultivation tray  90  is taken out from the cylindrical space  60 . A device which inclines the cultivation tray  90  is mounted on the introducing/discharging-side lifting and lowering device  202 . 
     With such a configuration, the cultivation trays  90  of the plurality of unit plant cultivation devices I can be inclined by one conveyance unit drive device  181  so that only a small number of parts is required. 
     Further, a power portion is disposed outside the cylindrical space  60  and hence, maintenance can be easily performed. 
     In the above-mentioned embodiment, one end of the cultivation tray  90  is lifted by lifting and lowering the lifting and lowering table  125  thus inclining the cultivation tray  90 . However, it may be possible to adopt the configuration where a lifting and lowering unit such as a cylinder or a cam is separately mounted on the lifting and lowering table  125 , and one end of the cultivation tray  90  is lifted by the lifting and lowering unit. 
     In the above-mentioned embodiment, the light emitting members such as the LEDs  243  are mounted on the inner surface of the roof portion  6 . Accordingly, a height of the light emitting member (a height with respect to the cultivation tray  90 ) is always fixed and cannot be changed. 
     However, it may be possible to adopt the configuration where a height of the light emitting member is changeable. For example, when seedlings are young seedlings, heights of some or the whole light emitting members are lowered so as to make the light emitting members approach the seedlings. Further, it is desirable that the light emitting member disposed at the position where irradiation of light to the seedlings is difficult be turned off or its amount of light be reduced. 
     EXPLANATION OF REFERENCE SIGNS 
     
         
           1 : unit plant cultivation device 
           1   a : young seedling unit plant cultivation device 
           1   b : grown seedling unit plant cultivation device 
           2 ,  3 ,  150 : seedling growing unit 
           2   a : young seedling growing unit 
           2   b : grown seedling growing unit 
           5 : case 
           11 : inspection window 
           12 : tray mounting base 
           15 ,  154 : conveyance device 
           16 : illumination unit 
           17 : water supply/discharge facility 
           19 : conveyance unit 
           20 : pressing member connecting body 
           22 : pressing member 
           21 : moving-side engaging projecting portion 
           28 ,  161 : power transmission member 
           36 : pipe 
           37 : cooling water collecting trough 
           38 ,  90 : cultivation tray 
           55 ,  170 : connecting member 
           60 : cylindrical space 
           62 : linearly moving member 
           65 : air supply passage forming member 
           70 : conveyance-unit-side engaging portion 
           81 : air volume adjusting unit 
           84 : air supply port 
           85 : small-sized blower 
           91   a ,  91   b : overflow pipe portion 
           100 : comprehensive plant cultivation device 
           101 : tray carrying-in device 
           102 : tray exchange device 
           103   a : young seedling frame 
           103   b : grown seedling frame 
           108 : holding member 
           110   a, b, c, d : bottom support portion 
           112 : tray carrying-out device 
           118 : open/close member 
           125 : lifting and lowering table 
           181 : conveyance unit drive device 
           182 : cultivation tray inclining unit 
           216 : drive-side engaging member 
           220 : inclining engaging member 
           243 : LED