In darkness, segments ofhypocotyls from etiolated Phaseolus radiatus L. seedlings showed high growthrate in Ca2+-free medium, but their elongation was inhibited when Ca2+ (1mmol/L) was applied. Red light inhibited the elongation of segments with orwithout Ca2+ in the medium, and theinhibition was more significant whenCa2+ was present (Fig. 1 ). We foundthat the activity of covalently boundPeroxidase strongly increased, the activities of covalently bound β-1, 4glcanase and β-1, 3-glcanase markedlydecreased during inhibition of elongation (Figs. 2- 4 ). These findings indicated that these enzymes were responsible for hypocotyl elongation. Profoundchanges occurred during the time 2- 4h after darkness or red light treatment.Otherwise, the changes in enzyme activity of cell wall would be more no-ticeable when hypocotyls were treatedby a combination of red light and Ca2+than by either red light or Ca2+ alone.
