Responses Of Leaf Temperature And Chlorophyll Fluorescence Parameter To Soil Water Stress In Three Trees

The cholorophyll fluorescence parameters and leaf temperature ofthree trees（Platycladus orientalis （L.）Franco, Robinia pseudoacacia L．andQuercus variabilis Blume.） in hilly areas of Taihang Mountain were measuredand compared under field conditions using Amplitude Modulation fluorometer（MINI-PAM） made in Germany Walz Co., Ltd and thermocouple made inBeijing CID Co., Ltd. Air temperature, solar radiation, air relative humidity andwind speed were monitored at the same time. This thesis systematically analyzedthe daily variation and responses mechanism of the cholorophyll fluorescenceparameters and leaf temperature of three trees to water stress, and revealed thecorrelation between parameters and environmental factors. put forward anti-droughtindices of tested plants, and established the mathematics reaction model of the leaftemperature and environmental factors by stepwise regression analysis. The resultsare as follows:1. The trends of daily variation of leaf temperature in three trees were similar. With theincreases of the water stress intensity, the leaf temperatures of three trees wereincreased gradually, and the leaf temperature were low in the morning and night, highin the midday. Leaf temperatures were highest in every period of day under solidwater stress. Environmental factors obviously affected the leaf temperature of threetrees under the conditions with different degree of water stresses in the daytime. Thetrends of daily variation of leaf temperature and air temperature were accordant, andthe air temperature was the prime and vital factor on influencing leaf temperature.Curves of daily variation of leaf temperature in three trees were lower than airtemperature, except leaf temperature of Quercus variabilis Blume.to solid waterstress in ten o’clock to sixteen o’clock.2. F₀, F_m, F_v, F_v/F_mand F_v/F₀of three trees had good sensitivity to water stress in themorning. F₀were raised gradually under water stress, and amplitude of rise from lowto high in order were Platycladus orientalis （L.）Franco, Robinia pseudoacaciaL．and Quercus variabilis Blume. In contrast, F_m, F_v, F_v/F_mand F_v/F₀were declinedgradually under water stress, and amplitude of decline was greatest in Quercusvariabilis Blume.3. The daily variation of Yield、ETR and NPQ were regular under the conditions withdifferent degree of water stresses. The curves of daily variation of Yield wereconcave in three trees, with the heavier the degree, Yield were lower under waterstress. Quercus variabilis Blume declined most obviously, and Robinia pseudoacacia L took second place.4. The curves of daily variation of ETR were approximative unimodal curve or bimodalcurve under the conditions with different degree of water stresses. In normal watersupply ETR value of three trees were higher than the rest of the water treatment. Withthe degree of water stresses intensifies, ETR value fell obviously. Under water stressthe electronic transfer efficiency of three trees dropped and the ETR decline ofQuercus variabilis Blume was the most significant.5. The curves of daily variation of NPQ in three trees were same change rule andobvious unimodal curve. It achieved maximum at high noon. With the increases ofthe water stress intensity, NPQ of three trees were increased gradually, Platycladusorientalis （L.）Franco was most significant.6. F₀、F_m、F_v、F_v/F_m、F_v/F₀、Yield、ETR and NPQ could be used as indicators to identifydrought-resistant three trees. Drought resistance and adaptability of Platycladusorientalis （L.）Franco were the best, and Robinia pseudoacacia L took second place,Quercus variabilis Blume the worst.7. Leaf temperature and chlorophyll fluorescence parameters of three trees had a highcorrelation with the environmental factors.And Leaf temperature of three trees had ahigh correlation with ETR、NPQ and Yield. The relationship between leaf temperatureand photosynthesis was close, to a certain extent, leaf temperature affectedchlorophyll fluorescence parameters.