In soybean ABA is reported to be synthesized in the leaves andis exported in substantial quantities via the phloem (Hein et al.,1984). The lowering of the seed endogenous ABA level, through the seed filling, by UV-B radiation in our experiment indicates that most of the ABA in plants originates in leaf tissue and that any interference with the photosynthesizing leaves will reduce ABA level in developing soybean seeds. Liu et al. (2010) associated rapid increases in the rate of dry weight accumulation of the soybean seed with a high level of endogenous ABA in the seed. High concentration of ABA in the cotyledons of soybean genotypes was found to coincide with rapid uptake of sucrose, whilelower rates of sucrose uptake, later during seed filling, were paired