Abscisic Acid and Transpiration in Leaves in Relation to Osmotic Root Stress

Abstract

The adaptive response of plants to a decrease in osmotic potential of the root medium involves adjustments that facilitate the maintenance of their water balance. Thus Bernstein (2, 3) showed that turgor pressure may be maintained under salinization through a decrease in the osmotic potential of the whole plant. However, actual turgor may also be maintained by a decrease in transpirational water loss. Indeed, the turgor of salinized cotton plants was even higher than the controls accord- ing to Gale et al. ( They observed lower transpiration rates both in cotton and bean plants which had undergone complete osmotic adjustment and in onion plants which exhibited only partial osmotic adjustment. They con- cluded that salinity affected stomatal aperture by a mechanism other than reduced turgor.