Nuclear Research Laboratory, Indian Agricultural Research Institute, New Delhi-110012.
*Corresponding author's
1Present address: Assistant Professor, Department of Crop Physiology, Assam Agricultural University, Jorhat-785013.
A study was conducted with 15 day old sand culture grown seedlings of 21 genotypes of wheat to assess the induction potential of Nitrate Reductase (NR) in the leaves by nitrate and to assess whether induction of the enzyme is limited by uptake of nitrate by root. Feeding various concentrations of nitrate, rangning from 0 to 100 mM, to excised leaves as against seedling with intact roots showed that in 11 out of 21 genotypes, uptake of NO−3 by roots was not a constraint in the induction of the enzyme. In the remaining 10 genotypes root uptake limited the expression of induction potential significantly, but only at their maximal induction concentration. Maximal induction concentration showed genotype dependent variation, with a majority of the genotypes showing maximal induction with a concentration of 30 mM NO−3 in the media. However, in HD-2172 (G3) and WH-542 (G7) maximal induction occurred with 15mM, in HD-2329 (G2) and WJ-134 (G8) with 7.5 mM and in E-340 (G6) with 3.75 mM nitrate. A concentration of 100 mM NO−3 in the medium significantly inhibited the induced enzyme activity of all the genotypes with the exception of HD-2380 (G10) and Kalyansona (G17). In the former no significant effect above 15 mM was discernible while in the latter maximal induced activity was observed with 100 mM NO−3. E-340 (G6) which showed the least maximal induction concentration of 3.75 mM in combination with high induced enzyme activity, was a high biomass producer at low soil N level in field experiment. Such a trait could possibly be utilized in developing genotypes with high nitrogen use efficiency, especially under low soil nitrogen level.
Induction potential, nitrate reductase, wheat genotypes
