University of Wisconsin, Madison, Wisconsin 53706.
Plant Physiol. 1969 Nov;44(11):1547-52. doi: 10.1104/pp.44.11.1547.
Concurrent measurements of abaxial and adaxial stomatal resistance and leaf-water potentials of snap beans (Phaseolus vulgaris L.) in the field and growth chamber show that the stomata on the 2 surfaces of the leaflet react differently to water deficit. The stomata on the abaxial surface, which are about 7 times more numerous than on the adaxial surface, are not significantly affected at leaf-water potentials greater than -11 bars, but with further decrease in leaf-water potential, the resistance rapidly increases. On the other hand, the resistance of the adaxial stomata increases sharply at a leaf-water potential of about -8 bars and is constant at higher water potentials. The average stomatal resistance for both surfaces of the leaf, which is the major diffusive resistance to water vapor, to a first approximation acts as an on-off switch and helps prevent further decline in leaf-water potential. The relation between the leaf-water potential and the stomatal resistance links the soil-water potential to the transpiration stream as needed for soil-plant-atmosphere models.
田间和生长室中对菜豆（Phaseolus vulgaris L.）小叶的下表皮和上表皮的气孔阻力和叶片水势的同步测量表明，叶片两面的气孔对水分亏缺的反应不同。下表皮上的气孔数量约为上表皮的 7 倍，在叶片水势大于-11 巴时，下表皮上的气孔没有受到明显影响，但随着叶片水势的进一步降低，阻力迅速增加。另一方面，上表皮气孔的阻力在叶片水势约-8 巴时急剧增加，在较高水势时保持不变。叶片两面的平均气孔阻力是水蒸气的主要扩散阻力，它首先起到通断开关的作用，有助于防止叶片水势进一步下降。叶片水势与气孔阻力之间的关系将土壤水势与蒸腾流联系起来，这是土壤-植物-大气模型所需要的。
