春玉米苗期光合速率、蒸腾速率及气孔导度对土壤干旱的反应

为深入探索东北地区土壤水分含量变化对春玉米光合作用、蒸腾速率和气孔导度的影响，揭示玉米苗期干旱减产的生理机制，2010年春季在东北地区中部开展分期播种与土壤水分处理试验，进行土壤湿度、玉米苗情、净光合速率(NPn)、蒸腾速率(Tr)、气孔导度(Gs)等观测，分析它们之间的关系。结果表明，春玉米苗期叶片NPn、Tr和Gs与土壤水分变化之间分别呈二次函数关系，0~20 cm深土壤湿度在19.5%以上时，玉米叶片气孔导度大，光合作用和蒸腾作用旺盛；土壤湿度在19.0%以下，随着土壤湿度下降，NPn和Tr近于线性下降，土壤湿度每降低1个百分点，NPn和Tr分别下降1.6 μmol/(m2.s)和0.5 mol/(m2?s)。玉米叶片Tr和Gs与NPn的关系为线性函数，Gs和Tr每降低1 mol/(m2?s)和1 mmol/(m2?s)，NPn分别下降0.89和3.09 μmol/(m2?s)。玉米苗在干旱胁迫下气孔关闭，蒸腾作用减弱，使光合速率快速下降，进而抑制玉米营养生长，最终导致减产。

Response of Spring Maize Photosynthetic Rate, Transpiration Rate, Conductance on Soil Drought in Seedling stage

In order to explore the impact of soil moisture content on photosynthesis, transpiration rate and stomatal conductance of spring maize in northeast China, and reveal the physiological mechanism of yield reduction due to drought, water stress and interval sowing field experiments were carried out in the spring of 2010 in the northeast central area，the soil moisture, photosynthesis rate (NPn), transpiration rate (Tr) and stomatal conductance (Gs) of the maize seedling were observed, and the relationship between these factors was analyzed. The results showed that, there was quadratic function relation between soil moisture and maize Seedling NPn, Tr and Gs, respectively. When 0-20 cm soil moisture was over 19.5%, maize leaf stomatal conductance was higher and photosynthesis and transpiration rate was exuberant. When the soil moisture was under 19.0%, the NPn and Tr decreased linearly with declining soil moisture content, with every 1% decrease in the soil moisture content, NPn and Tr decreased 1.6 μmol/(m2?s)and 0.5 mol/(m2?s) respectively. The relation between Tr, Gs and NPn was linear function respectively, with Gs and Gs decreased 1 mol/(m2?s) and 1 mmol/(m2?s) respectively, the NPn decreased 0.89 and 3.09 μmol/(m2?s) respectively. Under soil drought stress, the maize leaf stomata closed and transpiration rate decreased, which lead to fast degradation of photosynthetic rate, furthermore inhibited maize growth and caused yield reduction.