Properties of potassium uptake by seedling roots of grape cultivars

Uptake rates of (⁸⁶Rb)K⁺ by seedling roots of six cultivars were measured and compared with K⁺ content of the root, K⁺ leakage, H⁺ efflux, and K⁺-ATPase activity of a partially purified plasmalemma fraction.Different cultivars showed significantly different rates of (⁸⁶Rb)K⁺ uptake. The uptake rates of the first (0–5 min) period did not correlate with K⁺ content of the seedling roots.The rates of uptake in the 10 to 30 min period, supposed to be active, were negatively correlated with K⁺ content of the root. Roots consistently leaked K⁺ during the first 5 min. This leakage was positively correlated with the endogenous K⁺ content of the tissue.H⁺ efflux was significantly different among the cultivars and correlated with the K⁺-ATPase activity of a microsomal fraction partially purified on discontinuous (18/34%) sucrose gradient. The relationships among transport parameters are discussed.Part of the present research was carried out at the Department of Agricultural Biotechnology of University of Padova, Italy.Part of the present research was carried out at the Department of Agricultural Biotechnology of University of Padova, Italy.