Abstract: A three-factor orthogonal experiment of temperature, relative humidity, and duration was carried out to examine the combined effects of high temperature and high humidity stress on tomato “Jinguan 5”. 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% relative humidity as control (CK). Sampling was carried out at 7, 14, 21 and 28 d after high temperature and high humidity stress. We measured growth index, antioxidase activity and chlorophyll content. The results showed that after high temperature stress, dry weight of tomato decreased significantly, and leaf area increased significantly when the treatment was at 35, 38 and 41 °C. Dry weight of tomato at 41 °C was 12.89% lower than that of CK. After high temperature treatment, the contents of chlorophyll a, chlorophyll b and carotenoids were lower than that of CK, and SOD, POD and CAT activities were higher than that of CK. With the increase of temperature, enzyme activities increased first and then decreased. The activities of SOD, POD and CAT were the highest at 38 ℃, which increased by 121.14%, 35.41% and 55.13%, respectively. Under the same temperature conditions, tomato grew best at the RH70% treatment. SOD, POD, CAT activity and chlorophyll content at RH70% were significantly higher than that at RH50% and RH90%. Appropriate high temperature could promote the growth of tomato and increase antioxidant enzymes. The growth of tomato was overcompensated when temperature was below 32 °C, but it was severely suppressed when temperature exceeded 38 °C. Under high temperature, increasing humidity could alleviate the stress of high temperature on plants to someextent, but such effect was limited and could not compensate the damage of high temperature stress.

Key words: coastal silviculture tree species, leaf functional trait, specific leaf area, nutrient resorption efficiency., N and P content, leaf dry mass content