Effects of La3+ on inward K+ channels at plasma membrane in guard cells

Abstract

The effects of La 3+ on inward K + channels at plasma membrane in vicia guard cells are inves-tigated using the whole-cell patch-clamp recording mode. It is shown that La 3+ on both sides of plasma membrane blocks inward K + currents in a concentration-dependent manner, indicating that La 3+ binding sites may exist on both sides of plasma membrane in guard cells in vicia. The dose response is fitted by the Michaelis-Menten relation characterized by an inhibitor constant Ki of 2.56±0.25 μmol·L −1 (outside membrane) and (1.18±0.11)×10 −15 mol·L −1 (inside membrane). Intracellular La 3+ has much stronger inhibitory effect on inward K + currents than extracellular La 3+ does, suggesting there may exist stronger binding sites inside membrane than outside membrane. Since ion channel activities of guard cells directly affect plant stomatal movement and water status, our results imply that rare earth elements might have potential practical values in regulating plant water status and strengthening plant drought endurance.