Protective Role of Pre-treatment with Different Phenolic Acids in Wheat Seedlings Against Heat Stress Induced Oxidative Damage

Abstract

The present study appraised the effects of pre-treatment with different phenolic compounds viz. gallic acid (GA), ferulic acid (FA), p-coumaric acid (p-CA), caffeic acid (CF) and salicylic acid (SA) on antioxidant defense system of two contrasting wheat cultivars grown under heat stress. HD 2967 is relatively thermotolerant cultivar whereas PBW 550 is relatively heat sensitive cultivar. In comparison to control, shoot and root lengths of HD 2967 were reduced by about 32% under heat stress whereas in PBW 550, shoot and root lengths were inhibited by more than 45%. Pre-treatment with phenolic acids enhanced the shoot and root lengths and biomass of growing tissues and maximum increase in the growth of HD 2967 was reported with p-CA, CF pre-treatments. Free radical scavenging capacities of stressed seedlings were significantly improved by pre-treatment with GA. MDA and H2O2 contents increased in both the cultivars on exposure to heat stress but the increase was more in the sensitive cultivar. In roots of thermotolerant cultivar, SA and CF pre-treatments were more effective in reducing lipid peroxidation whereas in case of PBW550, pre-treatments with all the phenolic acids reduced MDA content by more than 20%. Pre-treatment with different phenolic acids especially SA and CF reduced H2O2 content in HD2967 whereas, in the shoots and roots of PBW 550 maximum decrease was reported on pre-treatment with GA, SA, p-CA and CF. Pre-treatment with CF stimulated SOD, CAT, APX and GR activities in the stressed roots of HD 2967 and SOD, POX and GR activities in the roots of PBW 550. Therefore, this study revealed that pre-treatments with phenolic acids especially CF have the potential to activate ascorbate glutathione cycle in stressed HD 2967 seedlings as revealed by ascorbate peroxidase and glutathione reductase enzymes. Further, it can be inferred that application of these phenolic acids protects the heat stressed seedlings by playing a dual role i.e. in activation of the antioxidant machinery as well as in the regulation of the growth.