Abstract: An experiment with growth chambers was conducted to study the effects of air relative humidity (RH) on the photosynthesis and dry matter accumulation of tomato plant at 33 ℃ from 11:00 to 15:00. Three treatments were installed, i.e., 70%-80% (high RH), 50%-60% (medium RH), and 30%-40% (low RH, control). After treated for 25 days, the tomato leaf chlorophyll content and net photosynthetic rate in treatment high RH were significantly higher than those in treatment low RH, while the empty rate of tomato in treatment low RH was 18.4% higher than that in high treatment RH (P<0.05), suggesting that at sub-high temperature 33 ℃, 70%-80% air relative humidity could benefit the improvement of tomato photosynthesis and fruit quality.

Key words: sub-high temperature, Microcystis aeruginosa, compensation index, malondialdehyde.