Acclimation of Soybean Plants to Water Deficit : VI. Analysis of regulation of tissue potassium concentration in leaves and stems

Abstract

Changes in potassium (K) concentration (tissue water basis) of various plant parts caused by the soil water deficit were analyzed from their water and K content (dry weight basis). When soil water content (SWC) decreased, K concentration of leaves in all positions and of all parts of stem increased rapidly and was kept high as far as SWC remained low. The cause of this increase changed with time and differed among plant parts. A rapid decrease in tissue water content resulted in an increase in the K concentration of both stem and leaf at the first step of the soil water dificits. After, the period of the water dificits lasted more, K content of the leaf of water stressed plants became higher than that of the control, and this became the major cause of the higher K concentration. On the other hand, the reduction of tissue water content was still the major cause of higher K concentration in the stem. It was suggested that the stem and the root had a role of a reservoir for K, and K concentration of leaves was preferentially regulated at a favorable level at an expense of stem and root K when the period of soil water deficits extended.