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以盆栽棉花 (中棉 2 3号 )做为供试材料 ,通过人工遮荫 ,设计了 3种遮荫水平 (不遮光 (CK ) ,遮光 75 %(DN) ,遮光 40 % (SN )和高、中、低 3种水分组合处理 ,其土壤含水量分别为田间持水量的 85 %～ 10 0 % (高水分 ,HW )、65 %～ 85 % (中水分 ,MW )和 45 %～ 65 % (低水分 ,LW ) 探讨了土壤水分和遮荫水平共同作用对棉花苗期至蕾期中午的气孔导度、净光合速率、蒸腾速率和叶水势等的影响 高水分下 ,DN和SN的气孔导度比对照分别增加 16 69%和 2 8 0 1% ,净光合速率分别减少 45 74%和 2 0 5 4% ,中水分下 ,DN和SN的气孔导度分别增加2 8 86%和 2 3 2 8% ,净光合速率分别减少 3 1 97%和 1 64 % ,低水分下三者气孔导度没有显著差异 ,但DN和SN的净光合速率比对照分别减少 46 2 2 %和 13 45 % ;相同水分条件下 ,DN和SN的气孔导度不存在显著差异 ,但DN和SN的净光合速率差异显著 (低水分下除外 ) 回归分析表明 ,气孔导度随叶 -气水汽压差 (VPD)的增加而下降 ,且与净光合速率表现出较弱的相关性 土壤不分与遮荫水平对叶片蒸腾速率和叶水势的影响很小 ,CK、DN和SN之间不存在显著差异 除中水分下SN的胞间CO2 浓度 (Ci)与对照相比没有显著变化外 ,其它组合下的Ci均比对照显著增加
Three kinds of shading levels (CK, 75% (DN), 40% (SN) and high shading) were designed with potted cotton (Zhongmian No.23) , Medium and low water, the soil water content was 85% ~ 100% (high water content, HW), 65% ~ 85% (middle water content, MW) and 45% ~ 65% (Low Water, LW) The effects of soil moisture and shading on the stomatal conductance, net photosynthetic rate, transpiration rate and leaf water potential at seedling stage to bud stage at noon were studied. Compared with the control, the conductance increased by 16 69% and 2801%, and the net photosynthetic rate decreased by 45 74% and 20 05% respectively. Under medium water, the stomatal conductance of DN and SN increased by 2 866% and 2% The net photosynthetic rate decreased by 3197% and 164%, respectively. There was no significant difference in stomatal conductance under low water conditions, but the net photosynthetic rate of DN and SN decreased by 46.22% and 1345, respectively %. Under the same water conditions, there was no significant difference in stomatal conductance between DN and SN, but there were significant differences in net photosynthetic rate between DN and SN (except for low water) regression The results showed that stomatal conductance decreased with the increase of VPD and showed a weak correlation with net photosynthetic rate. The effects of irrigating and shading levels on leaf transpiration rate and leaf water potential were small , There was no significant difference between CK, DN and SN except for the intercellular CO2 concentration (Ci) under SN in water compared with the control, Ci in other combinations was significantly increased compared with the control