Study on the effects of NaCl on the photosynthetic CO_(2) and water exchanges in bean leaves

The net photosynthetic rate of bean seedling was decreased by NaCl. Leaf stomatal conductance and transpiration rate were obviously decreased. In the younger leaf, the internal CO_(2) concentration was decreased by NaCl, the photosynthetic stomatal limitation increased by NaCl. In the older leaf, on the contrary, the former increased, the latter decreased. The water use efficiency in the younger leaf was increased by NaCl, while that of the old leaf decreased by NaCl. Under NaCl stress, the drop of stomatal conductance in the younger bean leaf was not necessarily induced by its water relation change.