Nitrogen Nutrition, its Assimilation and Remobilization in Diverse Wheat Genotypes

Abstract

Nitrogen is an essential element required for plant growth and development. However, over-use of nitrogen fertilizer is not only costly but also environmentally unsafe. Therefore, identification of genotypes possessing higher nitrogen use efficiency (NUE) at sub-optimal dose of nitrogen is the key challenge. In this study, effect of nitrogen on the activities of nitrogen assimilatory enzymes, total soluble proteins and amino acids was studied in wheat genotypes of diverse physiology (viz., GLU 1101, GLU 1356, GLU 2001. Nitrogen was applied at recommended dose (RDN), RDN-50%, RDN-25% and RDN+25% using urea as a source. With increase of nitrogen rate, significant increase in the activities of nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase and glutamate dehydrogenase was noted, which caused an increase in protein and amino acid contents in all the genotypes. Activity pattern of studied enzymes revealed an increasing trend from tillering to anthesis stage and thereafter declined in parallel with decrease in protein and amino acid contents. Conversely, nitrogen and chlorophyll content showed a consistent decline with leaf growth. Genotypes GLU 1356 and GLU 2001 maintained higher activities of nitrogen assimilatory enzymes in parallel with higher NUE at RDN-50% and RDN-25%, while genotypes PH132-4836 and PH132-4840 were found to be promising at RDN+25%. A positive correlation of nitrogen assimilatory enzymes (nitrate reductase and glutamine synthetase) with NUE and nitrogen content was also observed indicating that these might be the rate limiting enzymes in nitrogen metabolism. In crux, 25% less than the recommended dose of nitrogen had significant influence on nitrogen metabolism especially in GLU 1356 and GLU 2001 due to high activities of nitrate reductase and glutamine synthetase. These nitrogen efficient genotypes may be exploited in enhancing wheat crop productivity under lower dose of nitrogen to save environment and input cost.

Effect of growth stages and fertility levels on growth, yield and quality of fodder oats (Avena sativa L.)

“…Treatment with nitrogen fertilization resulted in significant increase in free amino acids content (F=439.18, p<0.001). Similar results were observed in wheat (Kaur et al, 2015) and maize (Losak et al, 2010) crop. Yield: GFY increased significantly (F= 2781.08, p<0.001) with N fertilization.…”

Efficient Physiological and Nutrient Use Efficiency Responses of Maize Leaves to Drought Stress under Different Field Nitrogen Conditions

“…The photosynthetic capacities of leaves may be improved with N, as it can enhance the activities of photosynthesis-related enzymes [14]. In the present study, the application of N enhanced the leaf photosynthetic capacities under nondrought stress conditions, but the P n values decreased with higher N treatment rates under drought stress conditions ( Figure 5).…”

“…Since nitrogen (N) is a vital component required for the synthesis of chlorophyll and photosynthetic enzymes in plants, which directly and indirectly impact the photosynthesis of crops, its presence or absence can determine the overall yields of crops [14]. Drought stress strongly affects growth and N metabolism, while the application of N can contribute to drought resistance to a certain extent in many plants [15].…”

Leaf Gas Exchange and Fluorescence of Two Winter Wheat Varieties in Response to Drought Stress and Nitrogen Supply

“…It is generally acknowledged that reducing CO 2 diffusion from the atmosphere to the site of carboxylation due to stomatal closure and reduced mesophyll conductance, which in turn, contributes to a decrease in photosynthesis under water stress conditions [9, 10]. Nitrogen is an important component in the synthesis of plant pigments and photosynthetic enzymes in plants, which directly or indirectly affects photosynthesis of crops [11]. Nitrogen could enhance the stomatal regulation of plants, and also well maintain the physiological function of photosynthetic apparatus by increasing chlorophyll content, photosynthetic oxygen evolution rate and the light saturation point [12].…”