摘要： 本文研究了土壤干旱对小麦叶片渗透调节和光合作用的影响。小麦叶片水势、相对含水量、饱和渗透势、光合速率、蒸腾速率和气孔导度随土壤干旱程度加剧呈现出先缓降后陡降的趋势, 其变化的土壤相对含水量阈值相同。小麦旗叶的渗透调节能力约为0.5MPa, 不同叶位叶片渗透调节能力不同, 其强弱顺序为旗叶>；倒二叶>；倒三叶。干旱使叶片膨压丧失时的渗透势从正常水分处理的-1.61MPa降到-2.33MPa, 弹性模量从5.74MPa增加到6.35MPa。干旱条件下的光合速率、气孔导度、气孔限制值和叶片光合放氧能力都下降, 而细胞间隙CO₂含量增加, 说明光合速率的降低是非气孔因素即叶肉细胞光合活性限制的结果。

关键词: 土壤干旱, 渗透调节, 气孔因素, 非气孔因素

Abstract: The effect of soil drought on osmotic adjustment and photosynthesis of winter wheat leaves was reported in this paper. In stressed plants, leaf water potential, relative water content, osmotic potential at full turgor, photosynthetic rate, transpiration rate and stomatal conductance decreased only after the soil relative water content fell below the critical level(40%). The degree of osmotic adjustment was 0.5 MPa in wheat flag leaf. The adjustment ability declined with lowering of leaves in position. The osmotic potential value in stressed leaves significantly dropped due to drought(from -1.23 MPa at full turgor to -2.33 MPa at zero turgor), but that of control leaves decreased from -1.23MPa to -1.61 MPa. Modulus of elasticity for the stressed plants increased from 5.74 MPa to 6.35 MPa, Under moderate and serious soil drought photosynthetic rate, stomatal conductance, relative stomatal limitation to photosynthesis and oxygen evolution in leaf blades declined, but intercellular CO₂concentration increased. The results showed that decrease in photosynthetic rate is mainly due to nonstomatal factor.

Key words: Soil drought, Osmotic adjustment, Stomatal factor, Nonsto-matal factor