Submitted to: Seed Science and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/31/2006
Publication Date: 6/1/2007
Citation: Ren, C., Bilyeu, K.D., Roberts, C.A., Beuselinck, P.R. 2007. Factors regulating the mobilization of storage reserves in soybean cotyledons during post-germinative growth. Seed Science and Technology. 35:303-317. Interpretive Summary: More soybeans are produced than any other legume crop in the world. Soybean seed have value for their composition that is high in protein and oil. The soybean seed is mainly comprised of two large storage organs called cotyledons where the protein and oil is stored. The composition of all seeds is comprised of stored reserves that generate the energy and nutrition required for germination and the support of a new seedling. Seed composition is related to seed vigor and seedling growth so it is important to understand how the stored reserves are digested and moved from the cotyledons to support germination and seedling growth. We studied factors that could affect the mobilization of the stored reserves found in soybean cotyledons during germination and early seedling growth. We found that hormones can significantly impact the rate of storage reserve use and also which stored reserves are used. As the seedling grows, growth in light or darkness, can also impact how the stored reserves in the cotyledons are used. This research is important to soybean breeders and biotechnologists that are targeting specific changes to enhance the composition of soybean seed for new food, feed, and industrial uses. We need to ensure that alterations in soybean seed composition do not negatively affect the germination or seedling growth and productivity of this important crop.
Technical Abstract: Cotyledons are the major storage organ of soybean (Glycine max L.) seeds that provide nutrients for seedling growth. Our objective was to study the mobilization of storage N and fatty acids in soybean cotyledons of seeds and its regulatory factors during germination and post-germinative growth. Cotyledons contributed 58% of their dry mass to support seedling growth at 9 days after imbibition (DAI). The mobilization of the storage reserves in cotyledons during post-germinative growth revealed that fatty acids decreased more rapidly than N. The presence or absence of testa had no effect on reserve mobilization, while light, gibberellic acid (GA) and sink strength significantly affected the mobilization of storage reserves. Growth in light promoted the mobilization of N from the cotyledons; while growth in the dark increased the mobilization of fatty acid. Differences in patterns of storage reserve mobilization in light or in dark grown seedlings were also observed for individual fatty acid components. Inhibition of GA biosynthesis by paclobutrazol (PAC) reduced storage reserve mobilization while exogenous GA reversed the inhibitory effect of PAC. Gibberellic acid promoted storage reserve mobilization indirectly by promoting seedling growth, but also by direct regulation of the mobilization of storage reserves. Sink strength was identified as the major influence affecting the mobilization of storage reserves.