ENHANCEMENT BY CALMODULIN INHIBITORS OF NITRATE REDUCTASE-ACTIVITY INCUCUMBER COTYLEDONS

Calmodulin antagonists, fluphenazine and chlorpromazine, strongly enha nced the activity of nitrate reductase (E.C. 1.6.6.1) in detached coty ledons of Cucumis sativus L. cv. Monastyrski. The relative enhancement by fluphenazine was much lower when the cotyledons were simultaneousl y treated with nitrate. The results are discussed with relation to the fluphenazine promotion of ion efflux, and it is suggested that increa sed membrane permability and higher nitrate level in cytosol may be pa rtly responsible for the induction of enzyme activivity. This may also apply to the promotion of nitrate reductase activity by some other in hibitors, and in some part also to the promotion by cytokinins.