Endogenous plant growth substances have been implicated in controlling many developmental processes of plants (Wilkinsonand Davies, 2002; Yang et al., 2004; Zhang et al., 2007). Liu et al.(2010) reported that ABA concentration in seed was positively cor-related with seed-filling rate. Similarly, a decrease in the rate of dry weight accumulation was associated with a sharp decline in ABA concentration. ABA may be involved in the stimulation of rapid unloading of sucrose into the testa of soybean and the ABA in cotyledons may enhance sucrose uptake by the cotyledons (Schussleret al., 1984).