By contrast, water stress decreased NR activity in the leaves, and the lowest value (P < 0.05) was observed for ungrafted plants at7% PEG followed by 5/cultivar and 8/cultivar plants (Fig. 6A and C). In the leaves, after 7 and 14 days of severe water stress,12/cultivar and 14/cultivar plants showed the highest NR activity levels – while the lowest values were observed in the ungrafted plants.