Effects of Heavy Metals on Stomatal Movements in Broad Bean Leaves

Water Channels Are Involved in Stomatal Oscillations Encoded by Parameter‐Specific Cytosolic Calcium Oscillations

“…Whether before or after stomatal oscillation had been induced, the addition of HgCl 2 was able to almost completely inhibit the occurrence of stomatal oscillations and the inhibitory effect of HgCl 2 was abolished by ME (Figure 3). Considering the strong and specific inhibition of water channels by HgCl 2 (Daniels et al 1996;Zhang and Tyerman 1999;Clarkson et al 2000;Sun et al 2001;Yang et al 2004b), the results of the present study suggest that water channels in guard cell membranes function to regulate water fluxes during stomatal oscillation.…”

“…Compared with ion channels, water channels play more direct roles in stomatal movement and the control of water fluxes across guard cell membranes, which control the changes in guard cell volume (Yang et al 2002(Yang et al , 2004b(Yang et al , 2005. The inhibition of water channels by HgCl 2 directly led to the impairment of stomatal oscillation regardless of whether it was applied before or after the induction of stomatal oscillation (Figures 4, 5; Table 2).…”

“…Further studies have demonstrated that the impairment of water channel activity by HgCl 2 can almost completely inhibit stomatal movement (Sun et al 2001;Huang et al 2002;Yang et al 2002Yang et al , 2004b, proving the functional role of water channels in stomatal movement. During stomatal oscillation, water quickly and rhythmically moves across the guard cell membrane and the regulation of these water channels should account for this quick action.…”

“…For other treatments, the epidermis was incubated in buffers containing 0.5 mmol/L LaCl 3 , 2 mmol/L EGTA, or 5 mmol/L TEACl in place of HgCl 2 for 15 min. The addition of HgCl 2 has been proven to effectively inhibit water channels in many studies (Daniels et al 1996;Zhang and Tyerman 1999;Clarkson et al 2000;Sun et al 2001;Yang et al 2004b). LaCl 3 and TEACl are putative channel blockers for Ca 2+ and K + , respectively; EGTA is a known effective chelator of Ca 2+ .…”

“…Water channels are highly expressed in the plasma and vacuolar membranes of guard cells (Kaldenhoff et al 1995(Kaldenhoff et al , 1996Sarda et al 1997;Sun et al 2001). Experiments using HgCl 2 and β-mercaptoethanol (ME) treatment (as a functional inhibitor of water channels and its reversing agent, respectively) suggested the involvement of water channels in stomatal movement (Sun et al 2001;Huang et al 2002;Yang et al 2002Yang et al , 2004b. During stomatal oscillation, water quickly and rhythmically moves across the guard cell membrane.…”