Biochemical Basis of Variability in Nitrate Reductase Activity in Wheat (Triticum aestivum L.) Genotypes

Significant differences in the activity of nitrate reductasein vivo and in vitro were observed among wheat genotypes, whenexpressed on a dry weight basis. The genotypes with high nitratereductase (HNR) activity exhibited an efficient nitrate inductionsystem. Availability of NADH seemed to be partially responsiblefor the low activities of the enzyme in genotypes categorizedas low nitrate reductase group (‘LNR). Biochemical analysisof the genotypes revealed that ‘HNR’ genotype hadmore active enzyme protein, high rates of enzyme protein synthesisand higher level of steady state nitrate reductase-mRNA relativeto those observed in ‘LNR’ genotype. ¹ Present address: Department of Botany, Faculty of Science,Hamdard University, Hamdard Nagar, New Delhi 110062, India.² Present address: Institut für Botanik, UniversitätHannover, 3000 Hannover 21, F.R.G.