Moisture Loss as a Prerequisite for Seedling Growth in Soybean Seeds (Glycine maxL. Merr.)

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Abstract
Rosenberg, L. A. and Rinne, R. W. 1986. Moisture loss as a prerequisite for seedling growth in soybeanseeds (Glycine max L. Merr.).—J. exp. Bot. 37: 1663–1674. As soybean seeds [Glycine max (L.) Merr.] develop, they undergo a change in seed moisture. When excised prematurely from the pod and planted, seeds do not exhibit seedling growth until 63 d after flowering (DAF) when the seed moisture has fallen below 60%. In contrast, seed germination (radicle protrusion) can occur when seeds as young as 35 DAF (68–79% moisture) are excised, but this germination docs not lead to comparable seedling growth frequencies unless seeds are first given a moisture loss treatment to artificially reduce their moisture below 60%. A moisture loss treatment applied at 35 DAF thus enables seed to undergo the transition from germination (cell expansion) to seedling growth (cell division and expansion) to the extent that treated immature seed have a vigour index comparable to seeds matured on the plant (100%). The pattern of protein synthesis in vivo was examined in 35 DAF seed using [35S]-methionine incorporation. When moisture loss treatment was applied for 24 h to 35 DAF seeds, seeds synthesized several new polypeptides when compared with untreated seeds at the same developmental stage. The same seed samples showed 0% seedling growth in the absence of moisture loss treatment and 80% seedling growth when the treatment had been applied. Moisture loss from soybean seeds appears to be a prerequisite for the synthesis of new proteins which may be part of the metabolic process or processes that allow the soybean seed to undergo the transition from seed germination to seedling growth.