Comparative studies on heat and drought tolerance mechanisms in wheat using biochemical traits
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Date
2014
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PAU
Abstract
In semi-tropical regions, particularly in the Punjab (India), drought and high-temperature stress are erious constraints for wheat production. Six wheat cultivars PBW 343, PBW 550, PBW 621, PBW 175, C 306 and HD 2967 were extensively characterized for biochemical and physiological parameters under heat and drought conditions. High temperature (HT) elevated activities of syringaldazine peroxidase (SPX), guaiacol peroxidase (GPX) and coniferyl alcohol peroxidase (CPX) in C 306 and HD 2967 cultivars while, drought stress accentuated arginine decarboxylase (ADC) and ornithine decarboxylase (ODC) activities in PBW 621 and PBW 175. Both heat and drought stress enhanced activities of diamine oxidase (DAO) polyamine oxidase (PAO) along with contents of H2O2. Amongst studied POXs, SPX activity was relatively high and coincided well with lignin deposition in leaves during vegetative stage while at 15 days post anthesis stage, CPX was the main peroxidase in the grain. Activity of ADC/ODC paralleled with putrescine and spermidine contents under drought stress condition. Higher build up of thiobarbituric acid reactive substances in PBW 343 and PBW 550 indicated higher membrane disruption during stress. Grain carbon metabolism was also altered under heat and drought stress condition as indicated by significant reduction in enzymes activities of ADP-Glucose pyrophosphorylase (AGPase), alkaline inorganic pyrophosphatase and phosphofructokinase (PFK) in conjunction with reduced starch content. However, contents of reducing sugars and fructans were increased while amylose and amylopectin content decreased. Correlation analysis revealed positive correlation of amylose with alkaline inorganic pyrophosphatase and starch with AGPase and PFK. Role of PFK was evident from correlation between AGPase and PFK indicating its predominant role in providing substrate for AGPase activity. Thousand grain weights decreased more under heat stress as compared to drought stress indicating higher severity of the former stress. Our results reveal variable response of cell wall peroxidases, amine oxidase and starch synthesising enzymes under two stress conditions. Increased activities peroxidases and contents of lignin, H2O2 and TBARS antioxidants, and other metabolites viz. Sugar and fructans alleviate the effect of heat and drought stress. Based on the results, we infer that cell wall peroxidase under heat stress and polyamines under drought led to enhanced abiotic stress tolerance for plant survival.
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Keywords
enzymes, weather hazards, planting, starch, amines, grain, wheats, drought stress, biological phenomena, developmental stages