Agronomy Department, Faculty of Agriculture, Kafrelsheikh University, P. O. BOX 33516, Kafr El-Sheikh, Egypt.
Wheat (Triticum aestivum L.) is widely cultivated in the Mediterranean zone where plants generally suffer from water stress during heading and reproductive stages. This research was carried out at the experimental farm of the faculty of agriculture, Kafrelsheikh University using two water treatments (water stress and well-watered), four N levels (0, 80, 160 and 240 kg ha-1) and two ascorbic acid levels (0 and 200 mg l-1). Water stress substantially reduced yield and related-traits compared with well-watered crop; however, AA application improved yield productivity and chlorophyll content was associated with the maintenance of leaf water status under water stress. Catalase (CAT) and peroxidase (POX) activity showed significant increases in plants treated with ascorbic acid (AA) under water stress. Among different nitrogen levels, the highest N level (240 kg N ha-1) performed better during 2012/2013 and 2013/2014 seasons. Under water stress condition the higher N level (240 kg ha-1), despite determining an increase in grain N content, did not imply an increase in NUE, due to a decrease in grain yield which positively related to N uptake. Exogenous application of ascorbic acid (AA) has been found very effective in mitigating the adverse effects of water stress, which might be attributed by activities of antioxidant enzymes (CAT and POX). In addition, inducing a stimulatory effect on all the yield-related traits. Maximum productivity and related traits were recorded under well watered condition treated by 240 kg N ha-1. Nonetheless, exogenously applied ascorbic acid has better able to produce appropriate productivity under water stress.