Effect of aluminum on potassium uptake by red spruce seedlings

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Abstract
Potassium uptake by roots of intact red spruce seedlings exposed to 0, 1, and 4 mg∙L−1 Al3+ was determined using kinetic analysis. Uptake parameters Vmax and Km were estimated by nonlinear least-squares analysis of K+ absorption data fitted to a combined active and linear uptake model. Roots treated with 1 mg∙L−1 Al exhibited enhanced potassium uptake for up to 72 h of aluminum exposure. K+ uptake in the presence of 4 mg∙L−1 Al also increased but was influenced by the duration of exposure to Al in solution. Comparison of kinetic parameters revealed an increase in Vmax in roots treated with aluminum. Km in both 1 and 4 mg∙L−1 aluminum treatments varied consistently with duration of exposure, characterized by an initial decrease in apparent carrier-site affinity followed by Km values trending toward control levels. These changes are hypothesized to result from a combination of physical and physiological changes in red spruce seedling roots induced by Al3+ in solution.