Abstract:
A method of forming an end seal ( 50 ) for a manufactured seed ( 22 ) is provided. The method includes providing a manufactured seed having an open-end ( 56 ) and immersing at least the open end of the manufactured seed in a sealing material ( 54 ) for a predetermined period of time. The method also includes permitting the sealing material to harden over the opened end of the manufactured seed to form a plug that seals the opened end.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    The present application claims the benefit of U.S. Provisional Application No. 60/560,711, filed Jun. 24, 2003. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to manufactured seeds and, more particularly, to a method of creating an end seal for a manufactured seed.  
         BACKGROUND OF THE INVENTION  
         [0003]    Asexual propagation for plants has been shown for some species to yield large numbers of genetically identical embryos, each having the capacity to develop into a normal plant. Such embryos must usually be further cultured under laboratory conditions until they reach an autotrophic “seedling” state characterized by an ability to produce their own food via photosynthesis, resist desiccation, produce roots able to penetrate soil and fend off soil microorganisms. Some researchers have experimented with the production of the artificial seeds, known as manufactured seeds, in which individual plant somatic or zygotic embryos are encapsulated in a seed coat. Examples of such manufactured seeds are disclosed in U.S. Pat. No. 5,701,699, issued to Carlson et al., the disclosure of which is hereby expressly incorporated by reference.  
           [0004]    Typical manufactured seeds include a seed coat, synthetic gameophyte and a plant embryo. The seed coat is suitably a cylindrical capsule having a closed end formed by a primary end seal and an open end. The synthetic gameophyte is placed within the seed coat and substantially fills the interior of the seed coat. A longitudinally extending hard porous insert, commonly known as a cotyledon restraint, may be centrally located within the synthetic gameophyte. The cotyledon restraint includes a centrally located cavity extending partially through the length of the cotyledon restraint and is sized to receive the plant embryo.  
           [0005]    The well-known plant embryo includes a radicle end and a cotyledon end. The plant embryo is deposited within the cavity of the cotyledon restraint cotyledon end first. The plant embryo is then sealed within the seed coat by at least one secondary end seal. There is a weakened spot in the secondary end seal to allow the radicle end of the embryo to penetrate the secondary end seal.  
           [0006]    In the past, crimping the sidewalls of the seed coat formed the end seal. Forming the end seal by crimping the sidewalls resulted in a seal that was not uniform in shape and usually allowed for undesirable variations in the internal depth of the seed coat. Further, such crimping methods did not create a reliable seal and typically broke as the seed coat was subjected to mechanical manipulation. The creation of the crimp was a process that requires a fairly significant amount of time. Moreover, such a process requires an empty seed coat because a die must be inserted into the seed coat upon which the crimp was formed. In addition, the formation of the crimp requires a secondary operation that flattens the folds of the crimp against the die to complete the crimping process.  
         SUMMARY OF THE INVENTION  
         [0007]    In accordance with one embodiment of the present invention, a method of forming an end seal for a manufactured seed is provided. The method includes providing a manufactured seed having an open end, and immersing at least the open end of the manufactured seed in a sealing material for a predetermined period of time. The method also includes permitting the sealing material to harden over the open end of the manufactured seed to form a plug that seals the open end.  
           [0008]    In another embodiment of the present invention, the sealing material is a wax. Further, the predetermined period of time is substantially between a range of 0.1 and 10 seconds. In certain embodiments of the present invention, the manufactured seed is immersed in the sealing material for a total of one second.  
           [0009]    The method of forming an end seal in accordance with the embodiments of the present invention has several advantages over currently available methods. As a non-limiting example, the method of the present invention provides a stronger and more reliable seal even under extreme mechanical manipulation. Thus, a method of forming an end seal in accordance with the present application results in an end seal that is more reliable, faster, and stronger than end seals formed by existing methods and can be applied to empty seed coats or seed coats filled with synthetic gametophyte and with a cotyledon restraint. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The foregoing aspects and many of the attendant advantages of this invention is best understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:  
         [0011]    [0011]FIG. 1 is a cross-sectional side view of a manufactured seed with an end seal formed in accordance with one embodiment of the present invention; and  
         [0012]    [0012]FIG. 2 is a cross-sectional side view of a seed coat for a manufactured seed and a reservoir of wax used to form an end seal. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]    [0013]FIG. 1 illustrates an end seal  50  constructed in accordance with the present invention for a manufactured seed  22 . As is disclosed in U.S. Pat. No. 5,701,699, issued to Carlson et al., the disclosure which is hereby incorporated by reference, well known manufactured seeds  22  include a seed coat  24 , synthetic gametophyte  26 , a cotyledon restraint  28 , a plant embryo  30 , a primary end seal  36 , and a secondary end seal  40 . The cotyledon restraint  28  is suitably manufactured from a hard porous material and includes a longitudinally extending cavity  10 . The cavity  10  extends through the primary end seal  36  and partially through one end of the cotyledon restraint  28 . The open end of the cavity  10  is known as a cotyledon restraint opening  12 . The cavity  10  is sized to receive the plant embryo  30  therein. The plant embryo  30  includes a cotyledon end  32  and a root end  34 .  
         [0014]    The secondary end seal  40  seals the cotyledon restraint opening  12 . The end seal  40  is suitably formed from a sheet of polymeric film and includes a prestressed area  38 . The prestressed area  38  is centrally located above the cotyledon restraint opening  12 , as is disclosed in greater detail below. Such an end cap  40  is disclosed in U.S. Pat. No. 6,470,623, issued to Hirahara, the disclosure of which is hereby expressly incorporated by reference.  
         [0015]    Manufacture and attachment of the end seal  50  may be best understood by referring to FIG. 2. Preferably, the end seal  50  is formed after the seed coat  24  has been filled with at least the gametophyte  26  and cotyledon restraint  28 . In other embodiments, the end seal  50  is suitably formed before the seed coat  24  is filled with any material, such as the gametophyte  26  and cotyledon restraint  28 . In both embodiments, the seed coat  24  is positioned above a container  52  filled with a thermoplastic sealing material  54 , such as wax or wax mixture. For ease of illustration, FIG. 2 depicts an empty seed coat  24 . It should be apparent that a filled seed coat  24  is also within the scope of the present invention.  
         [0016]    In certain embodiments, the container  52  is heated to raise the temperature of the sealing material  54 . In such embodiments, the sealing material  54  in its solid state is placed within the container  52 . Heat is applied to the container  52  until the sealing material  54  changes state to a fluid. In other embodiments, the sealing material  54  may liquefied outside of the container  52  and then poured into the container  54 .  
         [0017]    Although wax is the preferred sealing material, additional types of sealing materials are also within the scope of the present invention. As a non-limiting example, any thermoplastic material capable of changing states in response to a change in temperature, such as plastic, is also within the scope of the present invention.  
         [0018]    An open end  56  of the seed coat  24  is immersed within the sealing material  54  for a predetermined period of time. The predetermined period of time, sealing material  54  used, and temperature of the sealing material  54  when it is disposed within the container  52 , all affect the shape and thickness of the resulting end seal  50 . Each of the foregoing parameters may be varied to control the shape and thickness of the end seal  50 . As a non-limiting example, if the seed coat  24  is soaked in the sealing material  54  for a period of time exceeding the time it takes for the sealing material  54  to adhere to the open end of the seed coat  24 , the sealing material  54  flows off the end of the end of the seed coat  24  to create a nipple-like protrusion.  
         [0019]    The length of time the seed coat  24  is immersed within the container  52  is determined by observation. Specifically, after the seed coat  24  is removed from the container  52 , the resulting end seal  50  is observed to ensure that a proper seal between the end seal  50  and the seed coat  24  has been formed. In certain embodiments of the present invention, the predetermined period of time may range between 0.1 seconds and 50 seconds, or longer. In another embodiment, the range is between 0.1 and 8 seconds. In still yet another embodiment, the seed coat  24  is immersed within the sealing material  54  in a range between 0.5 to 5 seconds. In yet another non-limiting example, the seed coat  24  is immersed in the sealing material  54  for one second. It should be apparent to one of ordinary skill that the soak time may be shorter or longer than those set forth above, and therefore, such times are also within the scope of the present invention.  
         [0020]    It has been discovered that depending on how long the seed coat  24  is immersed within the sealing material  54 , the depth to which the seed coat  24  is immersed within the sealing material  54 , and the density and temperature of the sealing material  54 , all combine to determine whether a seal is formed and also determines the shape of the end seal  50 . Thus, adjusting various parameters, such as the time that the seed coat  24  is immersed within the sealing material  54 , results in end seals  50  of varying thickness and shapes.  
         [0021]    After the seed coat  24  has soaked within the sealing material  54  for the predetermined period of time, the seed coat  24  is removed from the container  52 . The sealing material  54  then drips down and off the seed coat  24  and the remaining sealing material  54  hardens to seal the open end  56  of the seed coat  24 . The sealing material  54  forms a plug that is attached to both the sidewalls and the ends of the seed coats  24 .  
         [0022]    While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention. As a non-limiting example, it should be apparent to one of ordinary skill in the art that forming an end seal  50  in accordance with embodiments of the present invention may be incorporated with an automated system. In other applications, the seed coat  24  may be manually dipped and soaked in the sealing material  54 . Thus, both automatic and manual methods of dipping the seed coats  24  within the container  52  are within the scope of the present invention.