DESICCATION TOLERANCE IN DEVELOPING SOYBEAN SEEDS - THE ROLE OF STRESS PROTEINS

The consistent correlation between desiccation tolerance in orthodox s eed tissue and an accumulation of certain ''late embryogenesis abundan t'' (LEA) proteins suggests that these proteins reduce desiccation-ind uced cellular damage. The aim of the present work was to test this hyp othesis. Exogenous abscisic acid (ABA) was used to elevate the level o f heat-soluble LEA-like proteins in axes from immature (30 days after flowering; mid-development) seeds of soybean (Glycine max [L.] Merrill cv. Chippewa 64). As the LEA-Like proteins accumulated in response to ABA, the leakage of all elements after desiccation and subsequent reh ydration markedly declined. Both LEA-like protein accumulation and the decline in desiccation-induced electrolyte leakage were apparently de pendent on the presence of ABA. Both effects of ABA were inhibited by cycloheximide. Light microscopy revealed a marked effect of the ABA on cellular integrity following desiccation. Osmotic stress also caused a decrease in desiccation-induced electrolyte leakage and stimulated t he accumulation of LEA-Like proteins. Our data are consistent with the hypothesis that the LEA-like proteins contribute to the increase in d esiccation tolerance in response to ABA, and are consistent with a gen eral protective role for these proteins in desiccation tolerance.