EFFECT OF IRRIGATION ON PHOTOSYNTHESIS AND QUALITY OF TOMATO SEEDLINGS UNDER ELEVATED TEMPERATURE.

Temperature in greenhouse is often elevated during tomato(Lycopersicon esculentum L.) plants growing season, which causes the change of crop water requirement. With the climate change, high temperature episodes will become much more common. Tomato seedlings were treated by 80% ETc (Evapotranspiration), 100% ETc and 120% ETc of irrigation amounts under elevated temperature in greenhouse. The influence of supplementary irrigation on photosynthesis and quality of seedlings were investigated. Results showed that both net photosynthetic rate (Pn) and PS II photochemical efficiency (Fv/Fm) in plants with 120% ETc irrigation were the highest, while the minimum fluorescence (Fo) was the lowest among treatments. With the decrease of Pn in treatments of 80% ETc and 100% ETc, the stomatal limitation values (Ls) increased significantly. Seedling health index and growth function showed the following trends: 120%ETc>100%ETc>80%ETc. There was a positive relationship between irrigation amount and physiological indexes in tomato seedlings exposed to elevated temperature. 80% ETc and 100% ETc worsened the effects of heat stress, while 120% ETc irrigation amount mitigated the stress and enabled plants to thrive under elevated temperature. [ABSTRACT FROM AUTHOR]