Benzatone-induced stomatal movement in epidermal peels from Chenopodium album L. II. Characterization of the response to different concentrations of KCL and CO2

Stomatal movement in abaxial epidermal peels of Chenopodium album L. in response to KCl and CO2has been investigated in the presence or absence of the herbicide bentazone. In darkness, minimal stomatal opening was observed at 500 μ l l-1CO2and low exogenous KCl concentrations, whilst considerable stomatal opening occurred at 50 and 100 x 10-3M KCl, as reported with other species. 10-4M Bentazone modified this response to produce wide opening at 0 to 10 x 10-3M KCl and inhibit opening at high KCl concentrations. This observation demonstrates the importance of exogenous KCl concentration in studies of the stomatal activity of metabolic inhibitors. In light, maximum stomatal opening was observed at 50 μ l l-1CO2with only 5 x 10-3M KCl but was gradually negated by increases in CO2concentration up to 5000 μ l l-1. Furthermore, stomatal opening induced by 100 x 10-3M KCl in darkness was also inhibited by increased CO2concentrations. In the presence of bentazone C. album stomatal responses to ambient CO2concentrations were markedly altered. However, as with the response to light and KCl, the effect of this herbicide was reduced by increasing CO2concentrations. It is suggested that bentazone may effect C. album stomatal movement by disrupting guard cell ion transport and that CO2may directly control this process.