A METHOD OF AND APPARATUS FOR HEATING PLANTS TO PROMOTE GROWTH AND A SEED PACK SUITABLE FOR USE IN CARRYING OUT THE METHOD

Abstract: A method of promoting plant growth and protecting plants from damage due to low temperatures which comprises heating the plants by means of microwave radiation. A seed package for use in growing plants under microwave radiation comprises a plastics envelope defining two adjacent compartments (12, 14) and a communicating bridge or passage (16) between the compartments (12, 14). The bridge or passage (16) is sealed off by a temporary seal (18). One of the compartments (14) contains at least one seed in a dry growing medium and the other compartment (12) contains a dose of water. When the package is subjected to microwave radiation, the temporary seal (18) is ruptured and the water from compartment (12) passes into the compartment (14) containing the seed, in order to initiate germination thereof. The envelope comprises bio-degradable plastics and is so designed as to be sufficiently degraded as not to impede growth of a plant from the seed originally contained in the package by the time that the plant has outgrown the space afforded by the respective compartment.

Description: DESCRIPTION OF INVENTION Title: "A method of and apparatus for heating plants to promote growth and a seed pack suitable for use in carrying out the method" THIS INVENTION relates to a method of heating plants to promote growth and or to protect plants from low-temperature damage and to a seed package which is of particular utility in relation to the growing of plants using the method. The invention also relates to apparatus for use in carrying out the method. It is well known to grow plants, on an agricultural or horticultural basis, in transparent or translucent enclosures such as unheated greenhouses, heated greenhouses or hothouses or equivalent structures such as tunnels or extended arches clad in translucent or transparent plastics film, as well as smaller scale structures such as low-level frames, cloches or the like. Such greenhouses and the like are, of course, generally adapted to utilize, so far as possible, solar radiation to maintain, around the plants therein, a temperature above that of the surroundings, thereby to produce accelerated growth of the plants. However, because the materials, such as glass, plastics panels or plastics films which are used for cladding conventional greenhouses or the like, provide relatively poor thermal insulation, some form of heating, additional to that provided by solar radiation, is normally required in cold weather or where the plants being grown are adapted to a substantially warmer climate than that in which the greenhouse is located. Traditionally such heating is generally provided by heating the air within the greenhouse, either directly or more usually indirectly by means of radiators or pipes supplied with water heated by burning gas, oil or other fossil fuels. As this conventional technique involves the heating of rather large volumes of air and as noted above, the heat insulating properties of conventional greenhouses are relatively poor so that much of the heat supplied is lost, heating costs in such a conventional arrangement tend to be relatively high. t is an object of the present invention to provide an improved method of heating plants to encourage growth and/or protect the plants from damage due to low temperature. According to one aspect of the invention there is provided a method of heating plants to encourage growth and/or protect the plants from damage due to low temperatures, comprising generating microwave electromagnetic radiation and directing the same at the plants. The method preferably includes accommodating the plants within an enclosure rendered reflective to microwave energy, and disposing an emitter of said microwave radiation so as to direct the same at the plants, the reflectivity of the enclosure to microwave energy serving to mimimise the loss of microwave energy from the enclosure. According to a further aspect of the invention there is provided apparatus for encouraging the growth of plants, or protecting the plants from damage by cold, including an enclosure which is at least partly reflective to microwave electromagnetic radiation, a plant-growing medium within said enclosure, and means in said enclosure for emitting and directing microwave electromagnetic radiation to the space within the enclosure. It is, of course, already well known to use microwave electromagnetic radiation to heat and thereby cook foodstuffs, the microwave radiation in such applications being generally provided by magnetrons. The present invention adapts the techniques known for cooking purposes to provide extended but much more gentle heating of living plants to promote the growth of the plants, or at least to protect plants from frost damage, for example. By contrast with known arrangements in which air is heated to heat the plant in contact with the air, in the method according to the present invention the plants are heated directly and whilst the plants will, of course, lose heat to the surrounding air, which will, in turn, lose heat through the walls of the greenhouse or other enclosure to the outside, this heat loss is substantially less than in a case where the air is heated directly. According to yet another aspect of the present invention there is provided a seed package comprising a plastics envelope defining two adjacent compartments and a communication between said compartments, a temporary seal sealing off said communication, one of said compartments containing at least one seed in a dry environment and the other of said compartments containing a dose of water, the arrangement being such that when said package is subjected to microwave radiation, said temporary seal is ruptured and the water passes from said other compartment into the compartment containing the seed, in order to initiate germination thereof. The envelope preferably comprises bio-degradable plastics and is so designed as to be sufficiently degraded as not to impede growth of plant from the seed originally contained in the package by the time that the plant has outgrown the space afforded by the respective compartment. The seed-containing compartment may also contain a growing medium such as sterile dry compost or synthetic loam, together with, if desired, a fertiliser. The envelope may be contrived as a so-called "bubble pack" with each seed and the respective water dose being provided in adjacent "bubbles" of a respective pair of such bubbles. Embodiments of the invention is described below by way of example with reference to the accompanying drawings in which:- FIGURE 1 is a sectional view of apparatus embodying the invention including a greenhouse in the form of a barn-like structure clad in rigid light- transmitting sheeting, FIGURE 2 is a sectional view of a variant apparatus including a greenhouse in the form of a tunnel or extended arch clad in light-transmitting flexible plastic sheeting, FIGURE 3 is a plan view showing part of a plant pack embodying the invention, and FIGURE 4 is a view in section along the lines IV-IV of Figure 3. Referring to Figure 1, a greenhouse 2 which is of substantially con¬ ventional construction (except in the respects noted below) is clad in a rigid sheet material such as sheet glass or a rigid plastics sheeting. A growing medium 3 such as soil or compost is provided in the greenhouse. A microwave emitter 5 is located centrally within the greenhouse and the walls, at least, of the greenhouse are rendered reflective to microwave radiation, for example by being lined with metal net or mesh or with βemi-light-transmissive and semi- reflective material such as polyester film, coated with a metal such as aluminium, or alternatively the glass or plastics panels forming the cladding of the side walls of the greenhouse may themselves be rendered semi-reflective by metallisation, for example by sputter-coating such cladding with metal. The emitter 5 is arranged to emit microwave radiation substantially transversely as indicated by arrows 7 to heat gently the plants growing between the emitter 5 and the lining 6. (The emitter 5 may, of course, be arranged to emit microwave radiation to either side of the greenhouse, although only emission to one side is illustrated). The emitter 5 may itself incorporate means, such as a magnetron, for generating microwave energy and in this case, where the greenhouse is of extended length, similar emitters 5 are disposed at intervals therealong. Alternatively, microwave energy from a single generator of such radiation may be lead, by way of suitable wave guides or the like, to microwave emitters or radiators disposed at intervals along the length of the greenhouse. In the variation shown in Figure 2 the greenhouse takes the form of a tunnel or extended arch clad in flexible plastics film 8, for example draped over and secured to hoop-shaped cross members arranged at intervals along the length of the greenhouse. Greenhouses of this general type are known per se. However, in the greenhouse of Figure 2, the cross members are so shaped that the flexible plastics cladding has a substantially parabolic or quasi-parabolic shape in cross-section as shown and the or each microwave emitter 5 is located substantially at the focus of the parabola and arranged to direct radiation upwardly as well as horizontally. Furthermore the plastics material cladding the greenhouse is rendered reflective to microwave radiation by sputter-coating the plastics film with metal such as aluminium, gold or the like. The sputter- coating of the plastics film 8 is such as to render the latter part light transmissive and part light reflective while still being reflective to microwaves. Becauβe of the parabolic form of the tunnel, microwave energy radiated from the emitter 5 and impinging upon the internal surface of the cladding is reflected back, substantially uniformly onto the plants within the greenhouse. In this arrangement a substantial part of the microwave energy reflected towards the plants by the film 8 penetrates the soil or other growing medium in which the plants are growing to promote growth. In the embodiments of Figure 1 and Figure 2 the cladding material may be as disclosed in greater detail in our co-pending U.K. Patent Application No. 8526157. The seed pack shown is in the form of a strip 10 comprising two superimposed layers of plastics film which, except in the region of "bubbles" 12, 14 and connecting bridges 16 are bonded together, for example by welding, adhesive or the like. One of the layers of plastics film is formed with depressions, which form the bubbles 12, 14, whilst the other layer is sub¬ stantially flat. In the arrangement shown, the "bubbles" are arranged in pairs, successive pairs being spaced apart at predetermined intervals along the length of the strip, each pair comprising a bubble 12 and an adjoining bubble 14. The connecting bridge 16 between the bubbles 12, 14, of each pair preferably comprises a region where both the upper and lower layers are flat and are in contact with one another or separated by only a very thin layer of an interposed temporary sealant, 18. Thus, where the plastics material of the layers is such that the superimposed layers will "cling" together of their own accord, the bridge 18 may simply comprise a region where the superimposed layers have been pressed together to provide this "clinging" action. Alternatively, the seal 18 may comprise a temporary and easily displaceable sealant, such as a non- toxic wax or grease. A more permanent bond is provided between the superimposed layers of the strip around the entire periphery of the composite formation defined jointly by the bubbles 12, 14 of each pair and the connecting bridge 16. Each bubble 14 contains a seed 20 in a dry state, surrounded by a dry growing medium, for example dry, sterile, natural or synthetic compost with, for example, if desired, an appropriate fertiliser. Each compartment 12 contains a quantity of water. The bubbles 12 are made transparent to microwave radiation, whereas the bubbles 14 may be treated, for example by metalisation, to render them reflective to microwaves or, alternatively, the encapsulation of the seeds 20 may have a water-permeable but microwave- reflecting coating. For example, such coating may be provided on the exterior of a pellet of the compost or compost/fertiliser mixture in which the seed is embedded. In use, the strip 10 is extended over the growing bed within a cloche, greenhouse, or the like, such as disclosed in our co-pending U.K. Patent Application No. 8528692 incorporating means for irradiating the interior of the cloche or the like and/or the growing medium therein, with microwave electromagnetic radiation. The strip 10 may be left on the surface of the growing medium or may be lightly covered with further growing medium. The seals 18 will remain intact, and the seeds 20 dormant, until such time as the microwave generating means is activated to subject the strip 10 and the surrounding or adjacent growing medium to microwave radiation, whereupon the doses of water in the bubbles 12 are heated and in turn heat the air included in the bubbles 12, causing a rise of pressure thereof, thereby separating the superimposed layers in the region of the bridge 16, breaking the seal 18 and allowing water to pass into the bubbles 14 to moisten the growing medium around the seeds 20. Alternatively, or in addition, the temporary seal 18 may be made of a material particularly susceptible to heating by microwaves and arranged to melt, soften, or break down when subjected to microwaves, to allow water to enter the bubbles 14. Whatever the mechanism utilised, the entry of water into the bubbles 14 causes the seeds 20 to germinate. The material of the strip 10 is preferably of bio-degradable plastics and is of such a thickness and nature that, by the time that the seedlings which develop within the bubbles 14 from the seeds 20 have become sufficiently developed to require more space than afforded by the bubbles 14, the material of the bubbles has substantially disintegrated allowing the roots and growing shoots of the seedlings to rupture the degraded plastics material readily, to extend into the surrounding growing medium.

Claims: CLAIMS 1. A method of heating plants to encourage growth and/or protect the plants from damage due to low temperatures, comprising generating microwave electromagnetic radiation and directing the same at the plants. 2. A method according to claim 1, including accommodating the plants within an enclosure rendered reflective to microwave energy, and disposing an emitter of said microwave radiation so as to direct the same at the plants, the reflectivity of the enclosure to microwave energy serving to mimimise the loss of microwave energy from the enclosure. 3. Apparatus for encouraging the growth of plants, or protecting the plants from damage by cold, including an enclosure which is at least partly reflective to microwave electromagnetic radiation, a plant-growing medium within said enclosure, and means in said enclosure for emitting and directing microwave electromagnetic radiation to the space within the enclosure. 4. Apparatus according to claim 3, wherein said enclosure is at least partly light transmitting. 5. Apparatus according to claim 4, wherein said enclosure has a cladding comprising a transparent material sputter-coated with a metal to render the cladding partly light-transmissive and partly light reflective, and at the same time reflective to microwave radiation. 6. A seed package comprising a plastics envelope defining two adjacent compartments and a communication between said compartments, a temporary seal sealing off said communication, one of said compartments containing at least one seed in a dry environment and the other of said compartments containing a dose of water, the arrangement being such that when said package is subjected to microwave radiation, said temporary seal is ruptured and the water passes from said other compartment into the compartment containing the seed, in order to initiate germination thereof. 7. A seed package according to claim 6 wherein the envelope comprises bio-degradable plastics and is so designed as to be sufficiently degraded as not to impede growth of a plant from the seed originally contained in the package by the time that the plant has outgrown the space afforded by the respective compartment. 8. A seed package according to claim 6 or claim 7 wherein the seed- containing compartment also contains a growing medium such as sterile dry compost or synthetic loam, together with, if desired, a fertiliser. 9. A seed package according to any of claims 6 to 8 wherein said envelope is contrived as a "bubble pack" with each seed and the respective water dose being provided in adjacent "bubbles" of a respective pair of such "bubbles".

Inventors: JOHNSON WILLIAM NEVIL HEATON, MCKENZIE NOEL ROBERTSON, JOHNSON, WILLIAM, NEVIL, HEATON, MCKENZIE, NOEL, ROBERTSON
Applicants: APPLIED AGRICULTURAL RES, APPLIED AGRICULTURAL RESEARCH LIMITED
Application year: 1986
Main classification: A01G7
IPC codes: A01C1, A01G7