Growth responses of wheat seedlings of different varieties to heat-stress and their relation to the antioxidant system state and osmolytes accumulation

Abstract

Background. In recent decades, Ukraine has been experiencing abnormally high temperatures and droughts in different seasons, including autumn. This creates stressful conditions for winter cereals, especially wheat, at the very beginning of ontogeny. A comprehensive study of the functioning of antioxidant and osmoprotective systems in the early stages of development for wheat varieties of different ecological and geographical origins has not been conducted yet. This study aimed to investigate the effect of heat stress on the growth of etiolated seedlings of seven varieties of winter wheat (Triticum aestivum L.) and the indicators characterizing the functioning of antioxidant and osmoprotective systems. Materials and Methods. Wheat grains of different varieties were germinated at 24 °C for three days in the dark. Subsequently, they were subjected to 4 h of heating at 45 °C in an air thermostat. Immediately after stress, the generation of superoxide anion radical (O2•‒) by seedlings, the content of hydrogen peroxide (H2O2), lipid peroxidation (LPO) products, catalase and guaiacol peroxidase activity, and also proline and soluble carbohydrates were analyzed. One day after heating, the relative inhibition of shoot and root growth was determined. Results and Discussion. The Antonivka and Tobak varieties demonstrated the highest ability to maintain growth after exposure to high temperatures; the Darynka Kyivska and Lira Odeska varieties were medium resistant. In the Doskonala, Bogdana and Avgustina varieties, a strong inhibition of shoot and root growth after heat stress was noted. In Antonivka, after high-temperature exposure, the O2•‒ generation increased slightly, while the content of H2O2 and LPO products did not change. In Tobak, Darynka Kyivska and Lira Odeska, the stress-induced increase in ROS formation and accumulation of LPO products was moderate. The hyperthermia-sensitive Doskonala, Bogdana and Avgustina showed a significant development of oxidative stress. Heat-resistant varieties had high catalase activity and increased total soluble carbohydrate content under heat stress. After exposure to high temperature, the proline content increased in all studied varieties, but no positive correlation was recorded between its amount and their heat resistance. Likewise, no significant correlation was found between the guaiacol peroxidase activity and the ability of varieties to maintain growth after heat stress. Conclusion. The high-level inverse correlation between catalase activity, soluble carbohydrate content, and the manifestation of oxidative stress effect indicates a significant contribution of these stress-protective system components to the adaptation of seedlings to heat stress. Indicators of the oxidative stress intensity and the functioning of individual components of the antioxidant system can be used to assess the heat resistance of wheat varieties at the early stages of development.