Submitted to: Seed Science Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 1995
Publication Date: N/A
Interpretive Summary: Soybean meal, the product of crushed seeds after oil is extracted, is important in animal husbandry because it is an inexpensive and reliable high protein feed supplement. However, it has recently become difficult to consistently produce a 44% protein meal because of a drop in protein content of a portion of the soybean crop. This led to increased research on nitrogen metabolism in soybean seeds because nitrogen is the essential component of amino acids, which are the compounds from which proteins are made. Many aspects of the problem are being explored including the movement of nitrogen compounds from the seed coat to the developing embryo. It is presently thought that there are no connections between the seed coat and developing embryo. Circumstantial evidence was obtained which suggested that they were connected. Observations, using scanning electron microscopy, showed that the surfaces of the seed coat and embryo were attached to each other during most of seed development. Also, it wa found that outgrowths from the cotyledon surface were embedded in the seed coat inner surface during maturation. This suggests that these forms of attachment keep the surfaces of the seed coat and developing embryo aligned. However, the significance of this alignment is not yet known. This information will help scientists to understand nitrogen metabolism, and will lead eventually to higher protein soybeans.
Technical Abstract: Holes are present on the inside surface of the seed coat in the apoplast of the soybean seed. The objective of this study was to determine if the holes were present during seed growth, maturation, and imbibition by observing the inside surface of the seed coat with low temperature scanning electron microscopy. The holes were found to be present throughout seed development, maturation, and imbibition. They were found free of the cotyledon surface and were not attached to it. However, the inner surface of the seed coat was occasionally attached to the surface of the embryo. At seed maturity, outgrowths of the cotyledon surface were found to be embedded in the cell wall of the inside surface of the seed coat. These structures were also observed in the imbibing seed. These points of contact, which were observed in the apoplast of soybean seeds, may align the embryo and seed coat during growth, desiccation and imbibition.