【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.更多还原