Antioxidant enzymes act as indicators predicting intension of acquired and maintenance of acquired thermotolerance and the relationships between basal, acquired and maintenance of acquired thermotolerance of tomato

Abstract

Heat stress seriously threats the crop production. Understanding different types of thermotolerance and illustrating the relationship of these types were essential. The activities of different antioxidant enzymes were determined after heat priming and acclimation for a heat resistant (R) and sensitive tomato genotype. We optimized the treatments for priming in acquired thermotolerance (AT) and acclimation in maintenance of acquired thermotolerance (MT). Then the intension of basal thermotolerance (BT), AT and MT were tested by using lethal temperature (45 °C). The peak of antioxidant enzyme activity (AEA) was identity with the priming time, indicating AEA can predict the optimal-priming time of AT and MT. Moderate high-temperature induced stronger thermotolerance than warmer high-temperature, but the priming time was longer than warmer high-temperature. Moreover, S needed longer priming time than R, due to the slowly AEA increasing and the AT of S also showed weaker than that of R. When the first-optimized-priming combined with secondary-priming for a reasonable duration, its thermotolerance further enhanced. Surprisingly, these optimized-acclimation treatments showed no difference in MT, suggesting secondary-priming could supply gaps produced by the first-optimized-priming of warmer high-temperature. In addition, R also responded the secondary-priming quickly than S, due to the quickly AEA increasing. While, after optimized-acclimations, thermotolerance of S showed no difference with R, suggesting secondary-priming can also narrow the thermotolerance-gap between S and R. Results from this study will accelerate screening of heat tolerant cultivars and provide insights into the choice of tomato cultivars in the changing temperatures environment.