Effects of calcium on growth and leaf ion concentrations of Gossypium hirsutum grown in saline hydroponic culture

Abstract

The optimum Ca²⁺ concentration for growth of cotton (Gossypium hirsutum cv. Acala SJ-2) was in the range 1 to 15 mol m⁻³ for plants growing in hydroponic culture with 100–150 mol m⁻³ NaCl. Most saline (but not sodic) soils contain higher Ca²⁺ concentrations. CaCl₂ was inhibitory to the growth of cotton above 20–50 mol m⁻³. Increasing concentrations of Ca²⁺ in the range 0–2 mol m⁻² drastically reduced Na⁺ accumulation in the leaves. As CaCl₂ concentrations were increased above the optimum for growth there was a further reduction in leaf Na⁺ accumulation, but this was more than offset by increased leaf Ca²⁺ and Cl⁻ concentrations. Leaf K⁺ concentrations were not much affected by changes in external CaCl₂ concentrations. The response of Mg²⁺ varied from an increase to a decrease with increasing external CaCl₂ and was influenced by nutritional status. There was no evidence that high Ca²⁺ caused a deficiency of Mg²⁺ in cotton. Except for Cl⁻, whose concentrations tended to decrease initially and then increase as the CaCl₂ concentration increased, the anions were largely unaffected by changes in external CaCl₂.