Effect of salt and soil water status on transpiration ofSalsola kaliL.

Transpiration of Salsola kali L. plants, grown in small pots under controlled environmental conditions, was followed through a drying cycle of the soil. Three different nutrient solutions were used during the preconditioning growth period: control (C), half‐strength Hoagland's nutrient solution; C plus 150mol m −3 NaCl; and C plus 150mol m −3 KCl. Soil water content at saturation at the beginning of the drying cycle was 20% (w/w). Both NaCl and KCl treatments modified the plants' response to changes in soil water status. The control plants transpired twice as much (per unit leaf dry weight) as the salt‐treated plants, even when the soil was at maximal water capacity. Transpiration of the control plants remained high, until the soil water content declined to 5%. After that stage the stomata of these plants closed abruptly. Transpiration of the salt‐treated plants started decreasing when the soil water content was approximately 16%, and did so gradually until all the available water was depleted. When transpiration was plotted against soil water potential a sharp decline in the transpiration of control plants was observed with the soil water potential decreasing from ‐0.04 to ‐1.2MPa. Transpiration of the salt‐treated plants decreased gradually over a wide range of soil water potential (−0.8 to −7.0MPa).