Study On The Responses Of Photosynthesis Under High-temperature Of Syringa.l

In order to understand the relationship between the photosynthetic characteristics and the physio-ecological factors, diurnal changes of photosynthetic rate of Syringa yunnanensis were survied researched under region of Beijing; The effects of high temperature on the leaf gas exchange and chlorophyll fluorescence were studied, and the heat-tolerance of the photosynthetic apparatus were also synthetically evaluated by a fuzzy membership function in four seedlings of lilacs. The results showed as follows:1) Syringa yunnanensis was belonged to a plant which was liked to a cool environment. And it's light saturation point and light compensation point were 768μmolm-2s-1 and 74.3μmolm-2s-1 respectively. And the light intensity was not the limiting factor on the photosynthetic rate of Syringa yunnanensis, because of the diurnal changes of light intensity didn't change largerly during the day.2) The correlation analysis and regression analysis were suggested that the photosynthetic rate of Syringa yunnanensis was significantly negetively correlated with the temperature(P<0.05), and significantly positively correlated with the stomatal conductance(P<0.01). So that we thinked that the temperature maybe one of the limiting factors on the photosynthetic rate of Syringa yunnanensis.3) The high temperature induced a decreased net photosynthetic rate in Syringa villosa and Syringa pinnatifolia, but increased in Syringa oblata and Syringa amurensis, which all the lilacs had distinct high stomatal conductance, transpiration and intercellular CO2 concentration.The carboxylation effciency in Syringa villosa and Syringa pinnatifolia were remarkable decreased compared with Syringa oblata and Syringa amurensis. So we suggested that the non-stomatal effect of limited distributing of syringa plays an important role on high temperature adapatation.4) While the NPQ were remarkably lower than normal temperature in S.oblata and S.amurensis.But theФPSII, Fv′/ Fm′, qP under high temperature treatment were significantly higher than normal temperature. We summarized that the higher leaf transpiration rate and light utilization efficiency could help to enhance their photosynthetic capacity for S.oblata and S.amurensis.5) A fuzzy membership function was defined to synthetically evaluate the high-temperature resistance ability of four species, and the result suggested that S.oblata and S.amurensis were the most heat-tolerant germplasm.