EFFECTS OF POTASSIUM-DEFICIENCY ON WATER RELATIONS AND PHOTOSYNTHESIS OF THE TOMATO PLANT

Potassium deficient (-K) and potassium sufficient (+K) plants were exposed to four days of water stress. Well watered -K and +K plants had comparable rates of transpiration. But +K plants had a larger leaf area and depleted the soil moisture to a greater extent on day 1 of stress. For days 2 and 3 their transpiration rate, leaf water potential and relative water content fell below those of -K plants. Well watered -K plants had a significantly lower rate of photosynthesis than +K plants. Photosynthesis of -K plants was more sensitive to reduction in plant water potential than that of +K plants. Reduction of photosythesis in -K leaves was due to impairment of photosynthetic capacity and not to stomatal closure. Growth was significantly reduced in -K plants. © 1990 Kluwer Academic Publishers.