Transformation of Soybean Cotyledon Cell during Water Absorption

Abstract

The spherical shape of dry soybean seeds is transformed into ellipsoidal structure by swelling after water absorption and the transformation is considerably different from that of other beans. The transformation of soybean seeds during water absorption was histologically investigated to clarify the reason of such a unique transformation. It was found by use of differential interference microscope that the amorphous and flat shapes of cotyledon cells in dry soybeans were transformed into a long ellipsoid by water absorption, because remarkable swelling arose in one direction, length (L) direction, of three directions of seed. On the other hand, wrinkles perpendicular to L direction were obviously observed in cell walls of the cotyledon tissue treated with pectinase by use of scanning electron microscope and it was proved that cotyledon cells were folded in L direction. Therefore, it was suggested that spherical beans are transformed into ellipsoidal ones by swelling because wrinkles of cotyledon cell walls are extended in L direction by water absorption and then cotyledon cells are swollen. Moreover, the structural transformation of soybean seeds was confirmed from the viewpoint of seed coats.