Water Stress, Water Use Efficiency, Carbon Isotope Discrimination and Leaf Gas Exchange Relationships of the Bush Bean

Water use efficiencies for the whole plant (WUE₁) and single leaves (WUE₁) were studied in a greenhouse as a function of soil moisture during four phenological stages of bush bean growth. WUE₁ increased significantly with soil moisture stress and attained its maximum value before the flowering stage. WUE₁ and WUE₁ were linearly related ( r = 0.92), and WUE₁ was correlated with the transpiration rate ( r = -0.87), stomatal conductance ( r = -0.80) and photosynthetic rate ( r = 0.81). Carbon isotope discrimination.), decreased as soil moisture decreased, and) was negatively correlated with both WUE₁ ( r = -0.92) and WUE₁ ( r = -0.88). There were significant differences in leaf N among water regimes.