Phytochrome mediated induction of nitrate reductase activity in etiolated maize leaves [accumulation]
1980
Rao, L.V.M. | Datta, N. | Sorpory, S.K. | Guha-Mukherjee, S. (Jawaharlal Nehru Univ., New Delhi (India). Plant Research Lab.)
The effects of red and far-red light on the enhancement of in vitro nitrate reductase activity and on nitrate accumulation in etiolated excised maize leaves were examined. Illumination for 5 min with red light followed by a 4-h dark period caused a marked increase in nitrate reductase activity, wherease a 5-min illumination with far-red light had no effect on the enzyme activity. The effect of red light was completely reversed by a subsequent illumination with the same period of far-red light. Continuous far-red light also enhanced nitrate reductase activity. Both photoreversibility by red and far-red light and the operation of high intensity reaction under continuous far-red light indicated that the induction of nitrate reductase was mediated by phytochrome. Though nitrate accumulation was slightly enhanced by red and continuous far-red light treatments by 17% and 26% respectively, this is unlikely to account for the entire increase of nitrate reductase activity. The far-red light treatments given in water, to leaves preincubated in nitrate, enhanced nitrate reductase activity considerably over the dark control. The presence of a lag phase and inhibition of increase in enzyme activity under continuous far-red light - by tungstate and inhibitors of RNA synthesis and protein synthesis - rules out the possibility of activation of nitrate reductase and suggests de novo synthesis of the enzyme affected by phytochrome
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