Heat stress is one of the major abiotic stresses affecting many biological processes, including agriculture productivity worldwide. Abiotic stress is the major factor that affects productivity of plants. Heat stress often causes adverse alterations in plant growth, development, physiological processes, and lead to reduction of yield. Plant responses to heat stress vary with the degree of temperature, duration and plant type. At extreme heat stress, cellular damage or cell death may occur within minutes, which may lead to a catastrophic collapse of cellular organization . Heat stress affects all aspects of plant processes like germination, growth, development, reproduction and yield [2, 3]. One of the major consequences of heat stress is the excess generation of reactive oxygen species (ROS), which leads to oxidative stress [4, 5]. A plant is able to tolerate heat stress up to some level by physical changes within the plant body and frequently by creating signals for changing metabolism. Plants alter their metabolism in various ways in response to heat stress, particularly by producing compatible solutes that are able to organize proteins and cellular structures, maintain cell turgor by osmotic adjustment, and modify the antioxidant system to re-establish the cellular redox balance and homeostasis [6, 7]. The excess electrons are …show more content…
100 mg of plant material was homogenized in 5ml of 80% ethanol and centrifuged at 8000 rpm for 10min. 100µl of supernatant was diluted up to 1ml with ethanol and 2ml Ninhydrin reagent was added. Mixture was kept for 30 min in hot water bath at 950C. Reaction was terminated in ice and absorbance was taken at 570 nm. Total free amino acid was calculated by plotting standard glycine.
Catalase activity was measured by the method of Aebi, 1974. 0.1 ml supernatant was addedtocuvette containing 1.9 ml of 50 mM phosphate buffer (pH 7.0). Reaction was started by the addition of 1.0 ml of freshly prepared 30 mM H2O2. The rate of decomposition of H2O2 was measured spectrophotometrically from changes in absorbance at 240 nm. Activity of catalase was calculated by extinction coefficient and expressed as units/mg protein.
Ascorbate peroxidase activity was estimated by observing the decrease in absorbance due to ascorbic acid at 290 nm (Nakano et al., 1981). 0.1 ml of enzyme extract was added to the 3 ml reaction mixture containing 50 mM potassium phosphate buffer (pH 7.0), 0.5 mM ascorbic acid, 1 mM EDTA and 0.1 mM H2O2. The reaction was started with the addition of 0.1 mM hydrogen peroxide. Decrease in absorbance for a period of 1min was measured at 290 nm in a UV visible spectrophotometer. Activity is expressed by calculating the decrease in ascorbic acid content