塔里木河上游胡杨与灰杨光合水分生理特性

在自然条件下对塔里木河上游优势树种-胡杨、灰杨的光合水分生理特性进行比较研究.结果表明,整个生长季胡杨、灰杨的光合速率(Pn)、蒸腾速率(Tr,除8月份)日进程均为单峰曲线,水分利用效率(WUE)变化无明显规律性.胡杨与灰杨12:00后Pn的下降主要取决于非气孔因素限制.胡杨Pn、WUE高于灰杨,而Tr低于灰杨,表明胡杨属高光合、低蒸腾、高WUE型树种,灰杨属低光合、高蒸腾、低WUE型树种.胡杨、灰杨枝水势(Ψw)、清晨与正午水势日进程均呈"V"字型曲线,胡杨水势日变幅、正午水势月变幅均小于灰杨,但两树种水势间无显著差异.胡杨与灰杨具有较强的水分吸收和减少水分丧失的能力,但胡杨调节气孔导度(Gs)控制蒸腾失水的能力较强,对干旱环境表现出更强的生态适应性,从而导致两树种产生了种群地理分化.

The photosynthetic and water physiological characteristics of Populus euphratica and Populus pruinosa in the upper reaches of Tarim River

Populus euphratica Oliv. And Populus pruinosa Schrenk. Distributed widely in the upper reaches of Tarim River, China.P. Euphratica played important roles in controlling the structure, function and sustainability of the ecosystems in Tarim basin because it had strong ability to survive in the desert. However, the population of P. Euphratica was declined due to excessively exploite soil and water resources by human beings. This result dangered directly sustainable development of oasis′ agriculture and ecological balance. Photosynthetic and water physiological characteristics of P.euphratica and P.pruinosa were revealed to illuminate their ecological adaptation, and supply theoretical base to utilize rationally resources, protect dominant population and restore degraded ecosystem. We measured the diurnal courses of gas exchange using Li-cor 6400(LICOR,USA)once every two hours from 8:00am to 20:00pm in different months and water potential with pressure chamber(SKPM1400, UK)under natural condition,2006,and got data on net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), intercellular CO_2 concentration (Ci), photosynthetic photon flux density (PPFD), leaf-to-air vapor pressure deficit (VPD), air to temperature (T_a),WUE was calculated by Pn/Tr. The results showed diurnal courses of P_n and Tr of P.euphratica and P.pruinosa were single peak curve in growth season except for August, but WUE were not significant variable regulation. Based on the analysis of stomatal limitation of photosynthesis using two criteria (Ci and Ls)suggested by Farquhar and Sharkey, it showed that the predominant cause of restricting P_n was non-stomatal limitation after 12:00. Compared with two plants, P.euphratica displayed the higher WUE because of its higher P_n and lower Tr, P.pruinosa displayed the lower P_n and WUE and the higher Tr. In the interval between of gas exchange measurements, we measured the water potential once every two hours. The diurnal courses of water potential and predawn, midday water potential were 'V' curve, daily variation range of water potential and monthly variation range of midday water potential of P.euphratica were the lower than that of P.pruinosa and water potential was not significant difference between two tree species. Both P.euphratica and P.pruinosa had the ability to endure drought with very low (more negative) water potential (Ψ_w) while P.euphratica had stronger ability to adjust stomatal conductance and decrease water loss according to degree of drought. Thus P.euphratica had better ecological adaptability and led to different population distribution.