ABSTRACT
Upregulation of antioxidant system provides protection against drought induced oxidative stress in plants. Proline, an important osmolyte, acts as ROS scavenger, membrane stabilizer and also as protectant of enzymes. In this study, we investigated the effect of proline pre-treatment on the inhibitory effects of water deficit stress in two contrasting wheat cultivars, i.e. PBW 644 (Drought tolerant) and PBW 621 (Drought sensitive). Seedling growth was adversely affected in both the cultivars grown under stress. Pre-treatment of seeds with 15 mM proline stimulated seedling growth of both wheat cultivars accompanied by increased activities of SOD, POX, APX and GR and the contents of glycine betaine, proline and total phenols in the tolerant cultivar. In PBW 621, CAT and APX enzymes were upregulated along with increased glycine betaine content. Proline pre-treatment enhanced the membrane stability of both wheat cultivars grown under stress, as revealed by the significantly reduced malondialdehyde content. The levels of endogenous H2O2 contents in proline treated stressed seedlings of PBW 644 were also markedly lower than those of the non-treated stressed seedlings. The results indicated that proline pre-treatment could improve drought tolerance by stimulating ROS detoxification pathways, especially in tolerant cultivars.