SA对蚕豆气孔运动和保卫细胞质膜K+通道的影响

Effect of Salicylic Acid on Stomatal Movement and K+ Channel on Plasma Membrane of Guard Cell in Vicia faba L.

水杨酸（salicylic acid，SA）作为植物体内一种内源信号分子，具有多种生理功能，尤其与通过诱导气孔关闭提高植物的抗病性密切相关。以蚕豆气孔为材料，利用表皮条生物分析、膜片钳等手段研究表明，SA浓度在1～1000μmolL^-1时诱导的气孔关闭具有可逆性，而10mmolL^-1时导致的气孔关闭不可逆；20UmL^-1的过氧化氢酶（catalase，CAT）与SA共同处理时可逆转SA诱导气孔关闭作用的83％～90％。以2步酶解法分离蚕豆保卫细胞原生质体并记录在不同处理条件下全细胞内向K^＋电流的变化。胞外100μmolL^-1 SA处理后20min可抑制内向K^＋电流的70％左右；同样，10μmolL^-1 H2O2处理后20min可抑制K^＋电流的47％。电极液中20UmL^-1的CAT可逆转SA抑制全细胞内向K^＋电流的52％左右，表明CAT可不同程度地逆转SA对保卫细胞内向K^＋电流的抑制作用，暗示H2O2可能通过抑制质膜内向K^＋电流而介导SA诱导的气孔关闭过程。

Salicylic acid（SA） is an endogenous signal compound with many functions especially in disease-resistance in plants. Previous studies have suggested that SA can inhibit catalase（CAT）, resulting in elevated levels of H2O2, which activate defense responses in plants. At present, it is accepted that H2O2 may be a new singal performing general functions in plant physiological processes. In this experiment, SA induced stomatal closure with a concentration-dependent manner, the changes in stomata apertures were reversible when the concentration of SA was 1 - 1 000μmol L^-1, but irreversible when the concentration of SA was 10 mmol L^- 1. The treatment with SA and CAT of 20 U mL^- 1 reversed the SA-induced stomatal closure by 83 % - 90%. The protoplasts of guard cells in Viciafaba L were isolated by two-step enzyme digestion. The voltage-dependent K^＋ -selective channels in the plasma membrane were recorded by whole-cell configuration. The current recorded should be carried by K^＋ based on the two results below： one was the determination of reversal potential and the other was the whole-cell current which was rapidly blocked by external 1 mmol L^-1 of Ba^2＋ . The whole-cell inward K^＋ currents were inhibited by 70% at 20 rain after treated by SA 100μmol L^-. Similarly, 10μmol L^-1 H2O2 inhibited inward K^＋ currents by 47% at the same time. But intracellular application of CAT abolished SA-inhibited inward K^＋ current by 52%. This indicated that H2O2 mediated SA-induced stomatal closure by inhibiting inward K^＋ channels on plasma membrane.