Department of Plant Science, University of California, Riverside, California 92502.
Plant Physiol. 1975 Mar;55(3):455-9. doi: 10.1104/pp.55.3.455.
Leaf resistance of Sesamum indicum L. increased when the humidity gradient between leaf and air was increased, at moderate temperatures, even though calculated carbon dioxide concentrations within the leaf decreased slightly. Mesophyll resistance remained relatively constant when humidity gradients were changed, indicating that the increases in leaf resistance were mainly caused by reductions in stomatal aperture and that nonstomatal aspects of photosynthesis and respiration were not affected. Low carbon dioxide concentrations inside the leaf decreased but did not eliminate resistance response to the humidity gradient. Internal carbon dioxide concentrations had little effect on resistance in humid air but had moderate effects on resistance with large humidity gradients between leaf and air. Stomatal response to humidity was not present at high leaf temperatures. Effects of humidity gradients on photosynthetic and stomatal responses to temperature suggested that large humidity gradients may contribute to mid-day closure of stomata and depressions in photosynthesis.
当湿度梯度在适度温度下增加时，芝麻（Sesamum indicum L.）叶片的阻力增加，尽管叶片内的计算二氧化碳浓度略有下降。当湿度梯度发生变化时，叶肉阻力保持相对恒定，表明叶片阻力的增加主要是由于气孔开度减小引起的，光合作用和呼吸作用的非气孔方面没有受到影响。叶片内的二氧化碳浓度降低，但并未消除对湿度梯度的阻力响应。低二氧化碳浓度对湿度空气的阻力影响较小，但对叶片与空气之间湿度梯度较大的阻力影响较大。在高叶片温度下，没有发现气孔对湿度的响应。湿度梯度对光合作用和气孔对温度响应的影响表明，较大的湿度梯度可能导致中午气孔关闭和光合作用下降。
