Ascorbic acid alleviates water deficit induced growth inhibition in wheat seedlings by modulating levels of endogenous antioxidants

The present investigation envisaged the potential of ascorbic acid through seed priming on the seedling growth and antioxidant response in three wheat cultivars i.e., PBW 644 (Drought tolerant), PBW 621 and HD 2967 (Drought sensitive) grown under water deficit stress. Imposition of water deficit stress reduced the root and shoot lengths by more than 11% in PBW 644, 18% in PBW 621 and 9% in HD 2967. On exposure to water deficit stress, catalase (CAT) was upregulated in the roots of all the three cultivars but declined in the shoots. Ascorbate peroxidase (APX) activity increased in stressed plants of tolerant cultivar but declined in sensitive cultivars except the shoots of HD 2967. Under water deficit stress, seed priming with 400 mu M of ascorbic acid increased shoot length of all the three cultivars by more than 19% when compared to stressed seedlings. Further, it enhanced the drought tolerance of PBW 644 by upregulating superoxide dismutase (SOD), CAT, APX and glutathione reductase (GR) enzymes accompanied by an increase in glycine betaine and H2O2 contents. Ascorbic acid treatment also protected sensitive cultivars from water deficit stress by increasing CAT, APX, GR and mono dehydroascorbate reductase (MDHAR) enzymes, ascorbate and glycine betaine contents in PBW 621 whereas SOD and peroxidase (POX) enzymes were upregulated in treated stressed seedlings of HD 2967. Lower levels of malondialdehyde (MDA) content in the treated seedlings of all the cultivars further signified the role of ascorbate treatment in alleviation of water deficit induced oxidative damage.