Effects of growth retarding compounds on chlorophyll accumulation and nitrate reductase activity in nitrate induced cucumber cotyledons

Abstract

Cotyledons were excised from 5-day old etiolated cucumber seedlings and .grown for 24 or 48 h in solutions of plant growth retardants: AMO-1618,B-Nine, CCC and phosfon D, supplemented with KNO3 (10-2M) in light. Nitrate reductase (NR) activity was determined in vivo. CCC and Phosfon D at high concentrations had no effect on nitrate reductase activity in 24 h tests. CCC at 5xl0-2 M enhanced NR activity in longer 48 h tests; Phosfon D was inhibitory in that case. AMO-1618 markedly decreased NR activity. B-Nine strikingly enhanced NR activity in KNO3 induced cytoledons; the effect was positively correlated with the concentration of B-Nine. Ali the compounds inhibited chlorophyll synthesis.