In our results, a decrease in NR activityin the leaves can be linked to a decline in the rate of photosynthesisdue to stomatal closure, according to Fresneau et al. (2007); or dueto a decrease in the NO 3−transport from root to leaves due to loss of turgor and lower transpiration flow (Sharma and Dubey, 2005;Yousfi et al., 2012). Water stress would limit the uptake and further the transfer of NO 3−to upper plant parts (Yousfi et al., 2012),and subsequently, a part of the nitrate uptake could be reduced in the roots. Observed differences in NR activity may depend on PEG concentration, time exposure, and plant combinations.