苏打盐碱胁迫下羊草光合速率日变化及其与影响因子的关系

采用Li-6400型光合作用测定系统对苏打盐碱化草地羊草光合速率和蒸腾速率的日变化进行测定，并对影响羊草光合和蒸腾速率的诸因子间相互关系进行了分析。结果表明，羊草光合速率和蒸腾速率日变化均呈“双峰”曲线，在苏打盐碱胁迫下，“双峰”出现时间提前。羊草光合速率日变化与蒸腾速率日变化间呈极显著正相关（r=0．9323，P〈0．01），水分利用效率在1d中基本保持不变。影响羊草光合作用和蒸腾作用的诸因子间都具有显著的相关性，但水分利用效率与气温、叶温的相关性不显著。羊草具有较高的水分利用效率，并且受温度的影响较小，这是羊草适应松嫩平原干旱气候和土壤苏打盐碱化胁迫的重要生理机制。

Relationship Between Diurnal Changes of Photosynthetic Rate and Affecting Factors of Leymus chinensis Under Saline Sodic Stress

Diurnal changes of photosynthetic rate and transpiration rate of Leymus chinensis were investigated by Li-6400 in saline sodic grassland, and relationship among the factors affected Pn and Tr was analysised. The results showed that change of photosynthetic rate and transpiration rate all was a double-peak curve in a day under saline-sodic stress, and the time appeared double peak was headed. The relationship between diurnal change of photosynthetic rate and transpiration rate of Leymus chinensis indicated highly significantly positive correlation （r=-0.932 3, P〈0.01 ）, and water use efficiency of Leymus chinensis was basically unchanged in a day. There were a significantly correlation among the factors affected Pn and Tr, but the relationship between WUE and temperature was not significantly. High WUE was an important physic-ecological mechanism of Leymus chinensis adapting to conditions of arid climate and saline-sodic soils.