Influence of exogenously supplied KCl on water binding mode of durum wheat leaf segments

Durum wheat leaf segments (Triticum durum Desf.) were incubated in solutions of KCl to test the effect of selective accumulation of ions, on tissues affinity for water. This was estimated trough an indirect estimate of the average enthalpy of water sorption. Leaf segments were collected from well watered plants grown in a controlled environment and were incubated in different KCl solutions. As increasing concentrations of KCl were included in the medium accumulation of K+ and Cl− ions and changes in the water-binding mode of the leaf segments were observed. Large increases in tissue affinity for water appeared when KCl concentrations in the medium were between 20-30mM and 50mM. These findings were repeatable in leaf segments of plants that differed in both growth stage and genotype. Relationships between tissue affinity for water and tissue K+ and Cl− content were examined. Tissue affinity for water did not change until the concentration of K+ in the leaf tissues reached approximately 50-55 mg/g dry weight, where large increase in strength of water binding was observed. Above this threshold tissue affinity for water was low even if K+ content increased.