The effect of foliar-applied magnesium on root cell membrane H+-ATPase activity and physiological characteristics of sugar beet

The aim of this study was to investigate the effect of foliar application of Mg on the leaf-to-root translocation of sugar and ATPase activity in the roots of sugar beet (Beta vulgaris L. Jolgeh). Furthermore, the effect of Mg on H+ secretion from the roots into the surrounding solution and solubility of Fe(OH)(3) (s) was investigated. Two Mg fertilizer sources i.e., MgSO4 and Mg-lysine complex (Mg-Lys) were used. A group of plants received only lysine (Lys) and a control treatment free of Mg and Lys was used. Foliar Mg spray significantly increased Fe(OH)(3) (s) solubilization in the root environment, at least in part due to higher passive H+ transport from the roots into the solution. The active transport of H+ and root activity of ATPase was significantly lower in the plants receiving Mg in comparison with those not receiving Mg. In contrast, the passive transport of H+ was higher in the Mg treatments as compared with the control. Our results suggest that foliar applied Mg can moderate the root activity of ATPase pump but it may affect Fe solubility in the root media by enhancing the passive H+ permeation across plasma membrane.