Changes in nitrate and nitrate reductase levels on restoration of molybdenum to molybdenum-deficient plants

Abstract

The effect of molybdenum on nitrate reductase was assessed by incubating wheat leaf fragments with potassium nitrate, with or without molybdenum, under lights supplying 2000 f.c. Enzyme activity was then estimated by measuring the nitrite produced by the fragments and released into the solution during 1 hr in total darkness.

Light stimulated the induction of nitrate-reducing activity while darkness was essential to obtain accumulation of nitrite.

Molybdenum deficiency in wheat depressed nitrate reductase activity and dry matter yield. Molybdenum caused a rapid increase in nitrate reductase in tissue from deficient plants but had no such effect on tissue from non-deficient plants.

The difference in response patterns between deficient and non-deficient plants, induced by molybdenum treatment could form the basis for a plant test for molybdenum deficiency.