Dear Dr. Balwinder Kumar

I want to know mechanism of stress tolerance in plants with special reference to nitrate, nitrite, NR, NiR etc. As we know proline plays an osmoprotectant role in plants grown under abiotic stress. Then, what is the role of nitrate, nitrite etc in plant's stress tolerance?

Dear Dr. Naik, 

Increased N assimilation (activity of nitrate reductase and N content)  is tightly related to higher allocation of N to Rubisco protein therefore higher photosynthetic-N use efficiency may be obtained under stress conditions. If NR activity protected by any means then N content automatically will increase and as a backbone of many metabolites N contributed to higher and /or protection of photosynthesis . Besides this NR has also found to interact with Nitric oxide and ABA but this area has not much work. 

Hi Vishal,

1. Please refer to this paper (2005) entitled " Nitrogen Containing Compounds and Adaptation of Plants to Salinity Stress" for the mechanisms and possible roles of these nitrogen-containing compounds (NCC) in plant stress tolerance. [ http://link.springer.com/article/10.1023%2FA%3A1002873531707 ]

2. NCC also provide osmoprotecion and osmotic adjustment functions when plants are under salinity stress.

Nitrogen fertilizer, NR and NIR activities in terms of drought stress response is species dependent. Additional nitrogen content in soil  and  plant tissue increase biosynthesis of RUBISCO like proteins thereby photosynthesis may increase in inherent drought tolerant cultivars or specices.  However, in most of the plants due to water deficit the enhanced nitrogen content may not evoke any effect due to  excess electrons and free radicals generated in the photosynthetic apparatus under high solar radiation. Mostly  drought stress occurs concomitant with soil moisture deficit and high light conditions.

In some cases excess nitrogen may be detrimental to plants under water deficit conditions.