Differential leakage of intracellular substances from imbibing soybean seeds

Leakage of electrolytes, substances absorbing UV light, and enzymic activities from imbibing soybean (Glycine max [L.] Merr.) seeds were compared to determine the extent that passive diffusion and cellular rupture contribute to each. Imbibing seeds with testae removed had average Arrhenius energies of activation (5 to 25°C) of 3.0 and 15.8 kilocalories per mole, respectively, for the leakage of electrolytes and embryo malate dehydrogenase activity. Leakage of embryo enzymes from imbibing seeds was dependent on loss of testa integrity and subsequent loss of cellular membrane integrity or inability to seal preexisting membrane discontinuities. These data suggest that electrolyte leakage from imbibing seeds is primarily by passive diffusion, whereas the diffusion of intracellular macromolecules is primarily dependent on physiological phenomena affecting membrane integrity. Kinetic data and examination of the composition of seed leachates indicated that the leakage of substances absorbing UV light during imbibition is due to both passive diffusion of low molecular weight solutes and macromolecules released from ruptured cells.