The Effect of Blue Light on the Induction of Nitrate Reductase in Etiolated Excised Maize Leaves

Abstract

Summary Illumination of etiolated excised maize ( Zea mays L. A 51–54) leaves for 5 min with blue light followed by a 4-h dark period increased the nitrate reductase (NR) activity 2-fold. Even 1 min of treatment enhanced the enzyme activity. The effect of blue light was not reversed by subsequent illumination with either red or far-red light. Continuous blue light enhanced the enzyme activity to the same extent as white light. Nitrate accumulation was not much affected by these light treatments. The enhancement of NR activity by a short pulse of blue light or continuous blue light was inhibited by tungstate, a-amanitin and cycloheximide, suggesting a transcriptional control and a de novo synthesis of the enzyme. Blue light enhancement of NR was only partially repressed by inhibitors of cyclic photophosphorylation and the synthesis of chlorophyll (Chl) under blue light was one third of that synthesized in white light. Thus, most probably the blue light effects are not mediated through photosynthesis or phytochrome.