Effects of La³⁺ and Eu³⁺ on outward potassium channels in Vicia guard cells

Abstract

Effects of La³⁺ and Eu³⁺ on outward potassium channels (K ⁺_out ) in Vicia guard cells have been studied by patch clamping technique. Extracellular La³⁺ inhibited K ⁺_out currents with a half-inhibition concentration (IC₅₀) of 81 µmol·L⁻¹. Interestingly, intracellular La³⁺ activated K ⁺_out currents at a free concentration of 1.13 × 10⁻¹⁴ mol·L⁻¹, and inhibited K ⁺_out currents at a free concentration of 5.86 × 10⁻¹⁴ mol·L⁻¹. Extracellular Eu³⁺ also activated K ⁺_out currents at concentrations of 10 µmol·L⁻¹ and 50 µmol·L⁻¹, and inhibited K ⁺_out currents at concentrations of more than 1 mmol·L⁻¹. The effects of La³⁺ and Eu³⁺ on K ⁺_out currents may contribute to regulation of the plant water status, which may be one of the mechanisms of the biological effect of rare earth elements.