CO_2浓度升高对极端干旱区多枝柽柳叶片水分利用效率的影响

Responses of water use efficiency of Tamarix ramosissima Ledeb leaf to elevated CO_2 concentration

采用美国Li-COR公司生产的LI-6400便携式光合作用测量系统,在2008和2009年生长季节对极端干旱区额济纳绿洲多枝柽柳(Tamarix ramosissima Ledeb.)叶片的净光合速率(Pn)与蒸腾速率(Tr)、胞间CO2浓度(Ci)随光照强度的变化。结果表明:胞间CO2浓度(Ci)随光照强度增强而减小;净光合速率(Pn)与蒸腾速率(Tr)均随光照强度增强而增大。在达到光饱和点后净光合速率(Pn)随光照强度增强而逐渐减小;水分利用效率(WUE)随光照强度增强呈先增大,达到最大值后又逐渐减小。蒸腾速率(Tr)和胞间CO2浓度(Ci)随CO2浓度升高而增大;净光合速率(Pn)和水分利用效率(WUE)在CO2浓度为200~600μmol/mol时随CO2浓度升高而增大,当CO2浓度升高至1 000μmol/mol时,水分利用效率(WUE)先增大后减小。

Interactive effects of elevated atmospheric CO2 concentration and water use efficiency(WUE) on terrestrial ecosystems play an important role in global carbon cycling.A large number of studies have been carried out on the relationship between the dynamics of elevated atmospheric CO2 concentration and related factors,but few studies have been done in these areas.Therefore,our objective is to conduct an experiment to improve our understanding with elevated atmospheric CO2 concentration and the characteristics of water use efficiency about Tamarix ramosissima Ledeb in extreme arid region.on early May to late November 2008 and 2009,the branches were put at the same height,and the changes of the net photosynthesis rate(Pn),transpiration rate(Tr),intercellular CO2 concentration(Ci) of Tamarix ramosissima Ledeb leaf with light intensity were measured under different CO2 concentration with a LiCor 6400 Portable Photosynthesis System;the response to CO2 enrichment was also compared.The results show that with enhanced light intensity,intercellular CO2 concentration(Ci) decreases;net photosynthesis rate(Pn) and transpiration rate(Tr) increase first,then gradually decrease after leaf get to light saturation point;water use efficiency(WUE) also increases first,but it gradually decreases after it reaches max value.With elevated CO2 concentration,transpiration rate(Tr) and intercellular CO2 concentration(Ci) increasing,net photosynthesis rate(Pn) and water use efficiency(WUE) increase when CO2 concentration elevates from 200 to 600 μmol/mol,and when CO2 concentration elevates to 1 000 μmol/mol,water use efficiency(WUE) increases first and then gradually decreases.The study results would do great help in the evaportranspiration modeling of terrestrial ecosystem carbon and water balance about Tamarix ramosissima in extreme arid region.