土壤水分胁迫对冬小麦旗叶光合特性的影响

Effect of Water Stress on Photosynthetic Characteristics of Flag Leaves in Winter Wheat

以土壤水分适宜做对照(CK),轻度水分胁迫(50%～70%)、中度水分胁迫(小于50%)3种处理在河北固城可控式土壤水分试验场,选择冬小麦灌浆初期的晴朗天气,采用Li-Cor 6400便携式光合作用仪,观测了3种处理的冬小麦旗叶光合作用参数的日变化。试验结果表明:土壤水分适宜时冬小麦旗叶净光合速率的日变化为"单峰型",未出现明显的"午休"现象,水分胁迫的处理都呈"双峰型",中度胁迫反而比轻度胁迫光合"午休"要短2h;3种处理的蒸腾速率日变化都呈"双峰型",气孔导度是反映叶片气体交换的重要指标,蒸腾速率与气孔导度成极显著正相关;土壤水分适宜或土壤干旱时冬小麦旗叶对环境变化的应变性较迟钝;轻度水分胁迫时冬小麦旗叶净光合速率比CK高2.8%～9.0%,蒸腾速率与CK基本相近,水分利用效率(WUE)比CK高10.6%～12.9%,这可能是一定程度的水分胁迫下冬小麦节水增产的生理调节机理。

Photosynthetic measurements were taken in the water controllable field at Gucheng,Hebei Prvince when winter wheat was in the early milk stage,and different water controls were designed for no water stress（CK）,low water stress （soil moisture 50% to 70%） and high water stress （soil moisture under 50%）. Diurnal changes of photosynthetic parameters of flag leaves in winter wheat were measured by Li-cor6400 under CK and different water stress conditions in shining days.The main results are：（1） Diurnal change of the net photosynthetic rate of flag leaves showed a single-peak type and there occurred no ＂noon-break＂ under CK conditions. Contrarily,all the diurnal changes of the net photosynthetic rate of flag leaves under different water stress conditions showed the double-peak type,and the noon break in winter wheat under the high water stress condition shortened for 2 hours compared with that under low water stress condition.（2） Diurnal changes of transpiration rate all showed the double-peak type under three water controls,and there was obviously positive correlation between transpiration rate and stomatal conductance.The feedback sensitivity of flag leaves kept at a low-level when winter wheat was in the appropriate soil moisture （CK） and soil drought （soil moisture under 50%） conditions.（3） The net photosynthetic rate of flag leaves and the water-use efficiency （WUE） under low water stress condition were over 2.8% to 9.0% and 10.6% to 12.9% higher than that under the CK condition respectively,which may explain the phenomena that the high yield of winter wheat can be gained at a water stress condition.