Light response curves of a typical desert plant Nitraria tangutorum under four rain addition treatments ( +25% , 50% , 75% and 100% of local mean annual precipitation) were measured with Li-6400xt Portable Photosynthesis Analyzer at the eastern edge of the Ulanbuh Desert, Dengkou, Inner Mongolia. The photosynthesis curves of light intensity were simulated by non-rectangle hyperbolic function and the parameters of photosynthesis were calculated to explore light response characteristics of N. tangutorum to different rain addition treatments. The parameters include the maximum net photosynthetic rate (Amax) , apparent quantum yields (AQY) , dark respiratory rates (Rd) , light compensation points (LCP) and light saturation points (LSP). Under the controlled condition, the Amax, AQY, Rd, LCP and LSP are 13. 41 μmol ·m-2·s-1, 0. 029 mol·mol-1, 0. 61 μmol·m-2 · s-1, 20. 63 μmol·m-2 ·s-1 and 481. 85 μmol· m-2 ·s-1, respectively. The results show that the net photosynthetic rate (Pn) , transpiration rate ( Tr) , stomatal conductance (Gs) , the maximum net photosynthetic rate, apparent quantum efficiency and dark respiration rate increased, but the water use efficiency decreased with the rain addition treatments. Therefore, the rain addition changed the physiological characteristics and improved photosynthetic capacity level of TV. tangutorum in varying degrees. The results also show that stomatal conductance is the main factor limiting the photosynthetic rate at the stage of light saturation.%在乌兰布和沙漠东缘即内蒙古磴口县,利用Li-6400xt便携式光合测定系统分析仪测定不同增雨处理(4个增雨处理的增雨量分别是当地年降水量的25％、50％、75％和100％)条件下,典型荒漠植物白刺的光响应曲线,采用非直角双曲线模型对曲线进行拟合,计算最大净光合速率(Amax)、表观量子效率(AQY)、暗呼吸速率(Rd)、光补偿点(LCP)以及光饱和点(LSP)等生理参数,研究白刺光合生理特性对人工模拟增雨的响应.结果表明:对照的Amax、AQY、Rd、LCP和LSP分别为13.41 μmol·m-2·s-1、0.029 mol·mol-1、0.61 μmol·m-2·s-1、20.63 μmol·m-2·s-1和481.85 μmol· m-2·s-1.增雨使白刺的净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、Amax、AQY和Rd升高,使水分利用效率(WUE)降低.增雨处理在一定程度上改变白刺的光合生理特性,提高白刺的光合生产能力.对胞间CO2浓度和气孔限制值的变化分析表明:气孔因素是限制光饱和阶段光合速率的主要因素.
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