Relation of Glycosidases to Bean Hypocotyl Growth

The enzymes beta-glucosidase, alpha-glucosidase, beta-galactosidase, alpha-galactosidase, and beta-xylosidase were detected in Phaseolus vulgaris L. var. Red Kidney bean hypocotyl tissue throughout the first 13 days of development with p-nitrophenyl glycosides as substrates. Activities of all enzymes except beta-glucosidase declined as a function of increasing tissue age. In contrast, beta-glucosidase activity increased rapidly 3 days after imbibition to a maximal activity at 5 days and then subsided to one-third the maximum by day 7. This activity peak immediately preceded the logarithmic phase of hypocotyl growth. This enzyme is strongly associated with cell walls during extraction, suggesting that it is wall-bound in situ. Various polysaccharide substrates were used to evaluate the specificity of this enzyme.