SUPEROXIDE ANION REGULATES THE K+ CHANNEL ACTIVITY AND STOMATAL MOVEMENT BY INCREASING GUARD CELL CYTOSOLIC FREE CALCIUM IN Vicia faba L
超氧阴离子通过提高[Ca2+]cyt调节保卫细胞K+通道和气孔运动

It is well known that the activated oxygen species, acting as signaling molecules, regulate various biological processes. Here using an epidermal strip bioassay, Laser Scanning Confocal Microscope and patch clamp technique. The first evidence that superoxide anion involves in K+ channel activity and stomatal closure was provided by increasing the guard cell cytosolic free calcium (cyt) in Vicia faba. The results indicate that 10-3~10-7 mol/L methyl viologen, which could generate superoxide anion, induce stomatal closure and inhibit stomatal opening. The effect of lower concentration(10-5~ 10-7 mol/L)methyl viologen-induced stomatal closure can be abolished partly by 2 mmol/L EGTA(chelator of Ca2+)?ascorbic acid and catalase. The cyt of guard cells was increased by 10 -7mol/L of methyl viologen. In addition, the inward K+ channel current in plasma membrane of guard cell was decreased after 15 min by adding 10 -7mol/L of methyl viologen. However, the decrease of K+ current induced by superoxide anion was blocked by adding 2 mmol/L EGTA, implying the inhibition of K+ channel activity resulting from Ca2+ signaling. This suggests that the mechanism of superoxide anion induced stomatal closure is mainly due to inhibition the K+ channel activity, which Ca2+ signal invoveld.