Correlation, between β-galactosidase and auxin-induced elongation growth in etiolated pea stems

β-Galactosidase, α-galactosidase, β-glucosidase and β-xylosidase were studied in relation to auxin-induced elongation of etiolated pea stems. Frozen-thawed sections were incubated in substrate solutions and individual enzyme activity was determined. Results were as follows: Only β-galactosidase activity was remarkably enhanced by 2,4-D in the concentration range which induced remarkable elongation. Auxin-induced increase in β-galactosidase activity reached maximum after 1 hr treatment of the section with 2,4-D (10−5 M), and was nearly constant afterwards. Auxin-enhanced β-galactosidase activity was observed even if auxin-induced apparent elongation was osmotically suppressed by mannitol. Correlation analysis indicated that β-galactosidase activity had a high positive correlation with auxin-induced elongation and increase in lateral face area of the section, while none of the other enzyme activities did. Measurement of in vivo distribution of four glycosidase activities in intact third internode of the epicotyl made clear that only β-galactosidase showed maximum activity in the zone where endogenous elongation was maximum.