Dynamics of Imbibition by Soybean Embryos

Measurements of the rate of imbibition by isolated cotyledons of soybean (Glycine max (L.) Merr cv Wayne) indicated that water uptake rates were slowed by low temperatures and by low initial moisture contents of the tissue. The role of water viscosity in the temperature effects on imbibition was examined, and a linear relation between imbibition rate and the reciprocal of viscosity was found only for seeds of very high initial moisture content. Adding solutes which lowered the surface tension, or increased the wetting ability of the water, yielded markedly increased rates of imbibition, especially for tissue of low initial moisture content. The data are interpreted as indicating a first component of water entry which is a wetting reaction influenced by the surface tension of the water, and a second component which resembles water flow through a porous matrix and is influenced by the water viscosity. We speculate that damage to soybeans during imbibition, such as in the case of chilling injury, may be particularly related to the initial wetting reaction rather than to the longer-term imbibitional rate.