Role And Relationship Of H₂O₂, NO, Ca～(2+) And PK In Light/Dark-regulated Stomatal Movement In Vicia Faba

The previous researches had showed the role and relationship of H₂O₂, NO, Ca²⁺, PK and other signals in ABA-induced stomatal movement. Although light and dark were the most important environmental factors that affected stomatal movement, there was little information available about the role and relationship of those signals in light/dark-regulated stomatal movement. In order to integrate an intricate network of signaling pathway in guard cells and develop the mechanisms of stomatal movement, the present investigation was to study the role and relationship of H₂O₂, NO, Ca²⁺and PK in light/dark-regulated stomatal movement in Vicia faba by epidermal strip bioassay and laser-scanning confocal microscopy.The results were as followed:1. Exogenous Ca²⁺ reduced stomatal aperture significantly in light, but it had no obvious effect on stomatal aperture in dark. EGTA (Ca²⁺ chelator) and LaCl_. (Ca²⁺ channels inhibitor) had no obvious effect on stomatal aperture in light, yet both increased stomatal aperture evidently in dark. The results above indicated that light decreased but dark increased the intracellular level of Ca²⁺ in guard cells.2. Exogenous H₂O₂ reduced stomatal aperture significantly in light, but it had no obvious effect on stomatal aperture in dark. It suggested that the level of H₂O₂ was low in light and was high in dark. Both in light and dark, EGTA and LaCl₃ could reverse H₂O₂-induced in light or dark-induced stomatal closure but could not decrease the level of H₂O₂ in the guard cells. However CAT (H₂O₂ scavenger), Vc(substrate for H₂O₂ removal) and DPI (an inhibitor of superoxide generating NADPH oxidases) could not reverse Ca²⁺-induced stomatal closure. It indicated that Ca²⁺ may function in the downstream of H₂O₂ in light/dark-regulated stomatal movement.3, SNP(exogenous NO donor) reduced stomatal aperture significantly in light, but it had no obvious effect on stomatal aperture in dark. It suggested that the level of NO was low in light and was high in dark. Both in light and dark, EGTA and LaCl₃ could reverse SNP-induced in light or dark-induced stomatal closure but could not decrease the level of NO in the guard cells; However c-PTIO (NO scavengers) and L-NAME (NO synthase inhibitor) could not reverse Ca²⁺-induced stomatal closure. It indicated that Ca²⁺ may function in the downstream of NO in light/dark-regulated stomatal...