镧对蚕豆叶肉细胞质膜外向钾通道作用研究

稀土元素对植物有许多生物效应，包括促进作物增产、促进种子萌发和苗期的生长等．稀土可提高植物叶绿素含量和净光合作用速率，同时提高幼苗抗旱性；La^3 还可对干旱胁迫下小麦幼苗叶片的伤害具有保护作用，然而，稀土元素对植物的这些生物效应的作用机理还不很清楚．

Effects of La3+ on Outward K+ Channels at Plasma Membrane in Vicia Mesophyll Cells

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.