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Reserve mobilization and starch formation in soybean ( Glycine max ) cotyledons in relation to seedling growth

1988; Wiley; Volume: 72; Issue: 3 Linguagem: Inglês

10.1111/j.1399-3054.1988.tb09159.x

1399-3054

Christopher S. Brown, Steven C. Huber,

Legume Nitrogen Fixing Symbiosis

Brown, C. S. and Huber, S. C. 1988. Reserve mobilization and starch formation in soybean ( Glycine max ) cotyledons in relation to seedling growth. ‐ Physiol. Plant. 72: 518–524. In germinating soybean ( Glycine max [L.] Merr.) seedlings, starch accumulated in the cotyledons during the first 5 days of seedling growth. Among 10 genotypes, the amount of starch accumulated after 5 days was relatively independent of light and appeared to be primarily related to the amount of sucrose depleted from the cotyledons during the same time period. Depletion of other reserves (e.g. protein and lipid) were not closely correlated with starch formation. In addition, the differences in starch formation were not related to differences in activities of certain enzymes that may be involved in the conversion of sucrose to starch, namely starch synthase (EC 2.4.1.21), ADP‐glucose pyrophosphorylase (EC 2.7.7.27), sucrose synthase (EC 2.4.1.13), neutral invertase (EC 3.2.1.26), and PPi‐linked phosphofructokinase (PFP) (EC 2.7.1.90). Starch synthesis did not compete with seedling growth, because among 10 genotypes, transient starch formation was correlated positively with seedling growth and cotyledonary photosynthetic rates. We postulate that starch is derived primarily from stored sucrose in the cotyledons and is not merely a result of ‘overflow’ carbon from other reserves. Starch formation also appeared to have a positive relationship with both early (0 to 5 days) and later (5 to 13 days) seedling growth, the latter perhaps due to enhanced cotyledon photosynthetic rates.