Abstract: In recent years, heat stress was more frequently occurred in tea gardens. However, few studies were focused on the approaches towards the improvement of heat tolerance in tea plants. In this study, Longjing 43 was used as experimental material to investigate the effects of various concentrations of MeSA on the net photosynthetic rate (Pn), the maximum carboxylation rate of Rubisco (V_c,max), the maximum RuBP regeneration rate (J_max), electrolyte leakage (EL), MDA content and antioxidant enzyme activities in tea leaves under heat stress. Results showed that 1βmmol·L^-1 MeSA could significantly increase Pn, V_c,max and J_max in tea leaves under heat stress. EL and MDA content in tea leaves increased significantly after heat stress, while the application of MeSA attenuated heat-induced increases in EL and MDA. In addition, the application of 1βmmol·L^-1 MeSA stimulated the activities of APX and CAT, leading to an efficient scavenging of hydrogen peroxide (H₂O₂) in tea leaves. In summary, we revealed that the applications of MeSA could improve photosynthetic capacity, strengthen the antioxidant system, reduce reactive oxygen species accumulation and lipid peroxidation in tea leaves under heat stress, and thus improve the tolerance of tea plants under heat stress.

Key words: salicylic acid, tea plant, heat stress, photosynthesis, antioxidant enzyme