蚕豆气孔运动中水通道和离子通道的作用和地位的探讨

 用不同浓度HgCl2、LaCl3和TEACl (Tetraethylammonium chloride)处理蚕豆(Vicia faba)叶片下表皮条，发现HgCl2能显著抑制气孔开闭，Ca2+通道阻塞剂LaCl3或K+通道阻塞剂TEACl处理也都有一定程度的抑制。三者的作用效果HgCl2>>LaCl3>TEACl。用HgCl2+LaCl3、HgCl2+TEACl或HgCl2+LaCl3+TEACl处理，则气孔开闭运动几乎完全被抑制。表明：蚕豆气孔运动中，保卫细胞胀缩主要是水通道直接参与保卫细胞与叶肉细胞间水流的调节引起的，离子通道起间接次要作用，二者共同引起保卫细胞体积变化而导致气孔开闭。

FUNCTIONS AND ROLES OF THE CHANNELS IN BROADBEAN STOMATAL MOVEMENTS

A network of ion channels, which controls stomatal movements, has been well characterized in the plasma and vacuolar membranes of guard cells. However, it is still not clear how water flows through the membranes to regulate guard cell volumes. Water channels, which can specifically and quickly promote the transportation of water, have been found in the plasma and vacuolar membranes of guard cells. It is suggested that water may flow through water channels during stomatal movements and water channels may be involved in stomatal movements with ion channels. Broad bean (Vicia faba L.) was grown in pots and watered every three days to keep the soil moisture level at 80%±5% soil water capacity. Three-week-old fully expanded leaves were harvested. The abaxial epidermis was peeled off and soaked in the MES/KOH buffer containing different salts in different concentrations. Stomatal movements and states were observed and open stomata/total stomata ratios recorded from randomly selected fields under the microscope. Stomatal movements appeared to be inhibited by the addition of HgCl2 at 0.8 mmol·L-1 concentration, while LaCl3 (at 0.5 mmol·L-1) or TEACl (at 5 mmol·L-1) (Tetraethylammonium chloride) had little effect. The effect of HgCl2 could beneutralized by 5 mmol·L-1 β-mercaptoethanl (ME). Stomatal movements were almost completely inhibited under HgCl2+LaCl3, HgCl2+TEACl, or HgCl2+LaCl3+TEACl treatments LaCl3, as Ca2+ channel blocker, could affect stomatal movements by the inhibition of the changes of guard cell cytosolic Ca2+ concentration or the blockage of Ca2+ signal transduction pathway. TEACl, as K+ channel blocker, inhibited the changes of guard cell cytosolic K+ concentration to affect stomatal movements. HgCl2 affected stomatal movements by the inhibition of water channels. All of them were involved in the regulations of water fluxes between guard cells and mesophyll cells directly or indirectly and affected stomatal movements significantly. Data appeared that they affected stomatal movements by HgCl2>>LaCl3>TEACl. Above results suggested that the environmental factors might affect stomatal movements in two ways: i) water channels activities were regulated and water flowed quickly across the membranes to control guard cell volumes. Some special stomatal movements, such as stomatal oscillation, could happen in this way; ii) ion channels activities were regulated and ions flowed across the membranes to change the osmotic or water potentials. Here water flows were transported with ion fluxes by co-transport or anti-transport. Previous studies have proposed pathways for regulating stomatal movements from the point of view of ions. However, from our study, it is evident that water channels may play an important part in regulating stomatal movements.