肥披碱草叶片光合特性研究

Study on the Photosynthetic Characteristics of Elymus excelsus

以大田生长的肥披碱草为试验材料,利用Li-6400型光合作用测定系统监测其叶片光合生理生态特性及其环境因子日变化,并利用相关分析和逐步回归分析法探讨了净光合速率和蒸腾速率与生理生态因子间的关系.结果表明:(1)肥披碱草叶片的净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs)的日变化均呈双峰曲线,具有明显的光合午休"现象;叶片水气压亏缺(VPD)和Tr及Gs的峰值出现时间不同步,胞间CO2浓度(Ci)不随气孔的降低而减小,抑制其光合速率的因子为非气孔限制;水分利用率(WUE)的变化呈单峰型,并且其上午WUE明显高于下午.(2)自然条件下,影响肥披碱草叶片Pn的主要因子是Tr和Ca(大气CO2浓度),影响Tr的主要因子是Gs和Ta(气温).(3)在干旱与半干旱自然条件下,肥披碱草的光补偿点(12.45μmol·m-2·s-1)、光饱和点(1 750μmol·m-2·s-1)、最大净光合速率(65.125μmol·m-2·s-1)、表观光量子效率(0.128 9μmol·mol-1)都较高,表现出较强的光环境的适应性和光能利用能力,是典型的阳性植物.

The ecophysiological photosynthetic characteristics of Elyrnus excelsus leaves and their environmental factors were measured using Li-6400 portable photosynthesis system. The relationship between the net photosynthetic rate （Pn） and leaf transpiration （Tr） and its physio ecological factors were studied by correlation and stepwise regression equation. The results showed that： （1） the diurnal change of Pn presented a bimodal pattern,and had a clear midday depression. The diurnal variation patterns of Tr and stomatal conductance （Gs） were also bimodal. The peak values of water deficit （VPD）,Gs and Tr appeared asynchronous. Intercellular CO2 concentration （Ci） did not decrease with the dropping of stomatal conductance. The mainly controlling factor of photosynthetic rate was non-stomatal limitation. The diurnal variation of water use efficiency （WUE） was one-peak curve,and the WUE of morning was significantly higher than that of the afternoon. （2）Under the natural condition, Tr and Ca （air CO2 concentration） were the key factors that affected the changes of Pn and the main factors that affected Tr were Gs and Ta（air tempreture）. （3）The light compensation point （LCP） of photosynthesis of Elymus excelsus in leaves was 12.45 μmol·m^-2 · s^- 1. The light saturation point （LSP） of photosynthesis was 1 750 μmol·m^-2 ·s^-1 ,the maximum Pn was 65. 125 μmol · m^-2 · s ^-1. The apparent quantum yield was 0. 128 9 μmol · mol. Elymus excelsus is adaptable widely to photo flux density and is a typical heliophyte.