干旱与正常供水条件下小麦光合午休及其机理的研究

A Study on Photosynthetic Midday Depression of Wheat and Mechanism under Drought and WellWatered Conditions

在小麦生育后期测定了干旱与正常供水条件下旗叶光合速率及其相应指标的日变化。结果表明，两处理条件下小麦午休开始的时间相同，午休的发生皆以气孔限制为肇端，非气孔限制随后才参与进来，但由于干旱胁迫使小麦光合机构受到一定程度的损伤（光合速率、气孔导度皆降低，细胞间隙ＣＯ２浓度升高），而使干旱条件下的小麦午休在降低的光合水平上进行。干旱胁迫使午休程度加重，通过气孔限制与非气孔限制在午休光合下降中所占比例的计算，表明这主要由气孔限制加剧引起。

The diurnal variations of photosynthetic rate and the corresponding parameters of wheat flag leaves were measured under drought and normal irrigating conditions during grainfilling stage.When plants were subjected to water stress, net photosynthetic rate and stomatal conductance decreased,while intercellular CO2 concentrations increased,suggesting that the photosynthetic organ was damaged in some extent.So the midday depression occured at a lower level of photosynthesis. However, the midday depression in both water stress and normal irrigating plants began at the same time, and was originated through stomatal limitation. But the degree of midday depression became higher under drought conditions which was mainly caused by severe stomatal limitation.