Glycine Betaine Induces Tolerance to Oxidative Stress in Cherry Radishes under High-Temperature Conditions

Abstract

Cool-season plant growth and development are impacted by high temperatures. As a biostimulant, glycine betaine is responsible for inducing tolerance to both biotic and abiotic stressors. However, the mechanism by which glycine betaine protects cool-season crops against high-temperature stress is not clear. In the present study, under the conditions of high temperatures (35 °C/30 °C day/night), cherry radishes (Raphanus sativus var. radicula Pers.) (Brassicaceae) were cultured for 9, 18, and 27 days, and different concentrations (0, 0.067, 8.79, 11.72, 14.65, and 17.58 mg L−1) of glycine betaine were applied to investigate the influence of glycine betaine on cherry radish biomass, quality, net photosynthetic rate, chlorophyll content, antioxidant enzyme activity, and endogenous hormone content under high-temperature stress. The results showed that, under high-temperature conditions, cherry radishes grew best with the 17.58 mg L−1 glycine betaine treatment. At day 27, comparing the 17.58 mg L−1 glycine betaine treatment with 0 mg L−1 glycine betaine under high-temperature stress, the cherry radish biomass increased by 44.7%, while the soluble protein and vitamin C content increased by 14.4% and 21.6%, respectively, the net photosynthetic rate and chlorophyll a content increased by 7.8% and 44.1%, respectively, and the peroxidase and catalase levels increased by 81.0% and 146.3%, respectively. On day 9, the auxin, abscisic acid, and glycine betaine contents significantly increased by 67.4%, 6.8%, and 32.9%, respectively, in comparing the 17.58 mg L−1 glycine betaine treatment with 0 mg L−1 glycine betaine under high-temperature stress. Therefore, the application of 17.58 mg L−1 betaine to cherry radishes grown under high-temperature stress had positive effects. The appropriate concentration of glycine betaine can improve the resistance of cherry radish to high temperatures and maintain yield.