Interactive effect of aluminum and calcium on root growth of Larix decidua and two co‐occurring acidophilous grasses

Abstract

Responses of three wild plant species (Larix decidua, Calamagrostis epigejos and C. villosa) to elevated aluminum concentrations were studied in a hydroponic system and in a soil suspension culture. Ameliorative effect of increasing Ca²⁺ level in the root environment was also tested. The results expressed as dependence of root elongation rate (RER) on Ca/Al molar concentration ratio in the solution revealed much higher sensitivity of the tree seedlings (Larix decidua) to the adverse conditions of acidic soils in comparison to the grasses. The RER declined to one half of its maximum value at the ambient Ca/Al ratio of about 1.0 in Larix decidua and at about 0.5 in Calamagrostis epigejos. No significant inhibition of RER was found for C. villosa in the range of ambient Al³⁺ and Ca²⁺ concentrations tested. The interspecific differences in aluminum toxicity were confirmed by calculated values of index of tolerance.

Measurement of RER of Larix decidua growing in aerated soil suspensions revealed significant rhizotoxicity of soil samples collected in the acidified sites of the Beskydy Mts. (Czech Republic). A synergic negative effect of elevated concentrations of Al³⁺ and deficiency of Ca²⁺ in the soil on root growth was obvious, but not sufficient to explain fully the strong inhibitory effect of soil suspensions.

Keywords:

• Larix decidua
• calamagrostis
• aluminum
• calcium
• soil acidity