Abstract: The effects of La ³⁺ on outward K⁺ channels at plasma membrane in vicia mesophyll cells were studied by using the whole-cell patch-clamp recording mode. It was shown that La ³⁺ on both sides of plasma membrane blocked outward K⁺ currents in a concentration-dependent manner. The dose response was fitted by the Michalis-Menten relationship characterized by an inhibitory constant K i of (76.59±9.28) μmol/L(outside membrane) and (5.80±0.62)×10^-15 mol/L(inside membrane) respectively, suggesting that intra-cellular La ³⁺ had a stronger inhibitory effect on outward K⁺ currents than extra-cellular La ³⁺ did. Since K⁺ remains the dominant osmoticum in mesophyll cells, the inhibition of outward K⁺ currents by La ³⁺ may contribute greatly to preventing the K⁺ loss and promoting turgor maintenance. These results implied that rare earth elements might have potential practical values in regulating plant water status and strengthening plant drought endurance.

Key words: Whole-cell patch-clamp, Mesophyll cell, Outward K⁺ channels, La ³⁺