Nitrate assimilation in contrasting wheat genotypes.

The plants grown in natural conditions do not express their full potential of nitrogen (N) utilization due to limiting availability of N at later stages of growth. There is a likelihood of manifesting their full potential under non limiting nitrogen supply. In our earlier studies with 15 day old seedlings, it has been shown that high nitrate reductase (HNR) genotype with higher efficiency of the enzymes of the nitrate assimilatory pathway resulted in higher potential of this genotype for N utilization as compared to low nitrate reductase (LNR) genotype. In this study, the two wheat genotypes viz. HNR (HD 2285) and LNR (HD 1981) were grown in pots and were given N in three splits, so as to improve the availability of N at later stages of growth. In another experiment, 15 d old seedlings grown in hydroponics were used for nitrate uptake studies. Examination of the flag leaves at different growth stages revealed that except for nitrate levels which were higher in LNR genotype, the uptake of nitrate from the medium, the activity of the enzymes of the assimilatory pathway including total N were higher in HNR genotypes. In HNR genotype, higher amount of N was mobilized to the grains as compared to the LNR genotype. From our study, it is concluded that that the higher N harvest of HNR genotype is due to the coordinated expression of all the enzymes of the N metabolizing pathway and holistic approach for modifying the plant for better NUE will be beneficial.