Abstract: To clarify the combined effects of high temperature and high humidity stresses on the growth of tomato, a threefactor orthogonal test of temperature, relative humidity and duration was carried out using “Jinguan 5” as material from June to September 2018 in the Agricultural Meteorological Laboratory in Nanjing University of Information Science and Technology. There were four levels of temperature: 32 ℃/22 ℃, 35 ℃/25 ℃, 38 ℃/28 ℃, 41 ℃/31 ℃ (day/night temperature), three levels of air relative humidity: 50%±5%, 70% ±5%, 90%±5%, and four durations (3, 6, 9, 12 d), with 28 °C/18 °C and 50%-55% humidity as control (CK). We measured photosynthesis parameters and rapid chlorophyll fluorescence induction kinetic parameters of tomato leaves. The results showed that when maximum temperature was within the range of 32-41 ℃, light saturation point (LSP), apparent quantum efficiency (AQE), maximum net photosynthetic rate (P_max), maximum photochemical efficiency (F_v/F_m), photosynthetic performance index (PI_abs), comprehensive performance index (PI_total), quantum yield for electron transfer (φ_Eo), quantum yield for reducing electron acceptor at the PSI receptor side (φ_Ro), light energy for electron transfer (ET_o/CS_m), and number of active reaction centers (RC/CS_m) decreased as temperature increased. The rapid chlorophyll fluorescence induction curve changed. J, I, and P phase decreased, with a negative value of ΔK. At high temperatures, LSP, AQE,P_max,F_v/F_m, PI_abs, PI_total, φ_Eo, φ_Ro,ET_o/CS_m,RC/CS_m and other indicators at the treatment with a humidity of 70% were significantly higher than that of 50% and 90%. There were no significant differences among indicators of different processing days and recovery days. Our results suggest that high temperature stress would destroy the structure and function of photosynthetic system of tomato seedlings. When the maximum temperature exceeds 35 ℃, increasing the air relative humidity to 70% can stabilize the photosynthetic reaction center and alleviate the damage of high temperature stress on the photosynthetic system.

Key words: plant , heat stress, molecular mechanism, proteomics.