Bound Water in Soybean Seed and Its Relation to Respiration and Imbibitional Damage

Abstract

In an attempt to understand the initial stage of seed imbibition—the wetting stage—we have examined water binding in dry soybean cotyledon tissue using water sorption isotherm curves. The sorption isotherms show three levels of water affinity: a region of strongly bound water at moisture contents below 8%, a region of weakly bound water at moisture contents between 8 and 24%, and a region of very loosely bound water at contents greater than 24%. The enthalpies of the water binding for the three sectors were −6 to −12.5, about −2.5, and about −0.5 kilocalories per mole water, respectively.