Protective Effect of External Ca^<2+> on Elongation and the Intracellular Concentration of K^+ in Intact Mung Bean Roots under High NaCl Stress

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The effects of Ca^<2+> in the external medium on intact mung bean roots under high NaCl stress were investigated. With increasing external concentrations of NaCl, mung bean roots showed suppression of elongation and a decrease in the intracellular concentration of K^+. Addition of Ca^<2+> to the external medium alleviated the inhibition of root elongation under the high NaCl stress and maintained a high intracellular concentration of K^+ in the elongating region of the roots. This counter effect of Ca^<2+> against the NaCl stress on roots was correlated with the ratio of [Ca^<2+>]/[Na^+]^2 in the external medium. A value above 5.0 × 10^<-4> mM^<-1> resulted in almost complete recovery of root elongation under various high concentrations of NaCl. Root elongation for 24 h under NaCl stress was correlated with the extent to which the intracellular concentration of K^+ was in excess of 10 mM. Maintenance of an adequate concentration of K^+ in root cells is essential for root elongation under salt stress. These findings indicate that Ca^<2+> prevents the leakage of intracellular K^+ and thereby supports the elongation of roots under salt stress.
日本植物生理学会の論文