Time-Course Studies on Accumulation of Hydrophilic Antioxidants to Different Stress Regimes Followed by Recovery in Contrasting Cultivars of Wheat

Under unpredictable climatic scenarios, drought is one of the major environmental constraints limiting plant growth and productivity in arid and semi-arid regions. Rapid recovery from drought is of paramount importance for the persistence and survival of different crops growing worldwide. The boiling soluble proteins, BSPs (proteins remaining soluble upon boiling in aqueous solution) forms an instrumental part of the response to water deficit conditions and might be of key importance for the survival of plants under unfavourable environmental conditions. These BSPs are typified by two unique properties: high hydrophilicity and high thermal stability. The main objective of the study was to determine drought-induced changes in the markers of oxidative stress along with modulation in the activity of the boiling soluble antioxidants in response to different stress regimes followed by re-watering in Triticum aestivum L. In this study, we determined the indices of oxidative stress (membrane injury index (MII) and lipid peroxidation in terms of malondialdehyde (MDA) content) and activities of boiling soluble antioxidant enzymes in seeds of sensitive and tolerant cultivars of wheat at different duration of stress (3, 6 and 10 days) followed by recovery (post stress harvest). Water content recorded a decline in the sensitive (PBW 343 and PBW 621) as well as tolerant (PBW 527 and PBW 175) cultivars in stress duration and cultivar dependent manner and this was reversed following re-watering in all the cultivars. Oxidative stress indicators also increased in all the cultivars at different stress intensities but this was reversed following re-watering in the tolerant cvs. PBW 175 and PBW 527. At 3 and 6 days, boiling soluble monodehydroascorbate reductase (BsMDAR), boiling soluble protein disulphide isomerase (BsPDI) activity increased in both the tolerant cvs. PBW 175 and PBW 527 whereas boiling soluble guaiacol peroxidase (BsGPX) increased in the sensitive cv. PBW 343. However, as the stress intensity increased to 10 days, BsMDAR, boiling soluble glutathione-S-transferase (BsGST) and BsGPX increased only in the tolerant cvs. PBW 175 and PBW 527, thus accentuating their cardinal roles in stress tolerance under harsh drought conditions. Upon re-watering the stress plants after 10 days, BsMDAR increased only in the tolerant cv. PBW 175. On the other hand, boiling soluble protein disulphide isomerase (BsPDI) increased in both the tolerant cv. PBW 175 and susceptible cv. PBW 343, but with a greater enhancement in the cv. PBW 175. Based upon our results, biochemical significance of the boiling soluble antioxidants in the cultivars of wheat differing in drought resistance during different stress intensities and recovery is discussed.