| Stomata in the leaf epidermis is responsible for regulating air exchange between plant and atmosphere. Guard cell regulates photosynthesis and transpiration, which play important roles in plant metabolism.Exogenous stimuli regulated stomata1movements resulting from volume changes of guard cells, which depend on ion transportation. Hence, signal transduction in guard cells has a close relation with stomatal movement.H+-ATPase in plasma membrane can be activated by exogenous stimuli through signaling molecules in plasma membrane. Then accelerated H+-efflux leads plasma membrane hyperpolarization and ion concentration cytoplasm changing. Finally stomatal movement (opening or closing) is induced.It has been suggeseted that proton pump is an positive regulator which accommodates stomatal movement by enhancing Ca2+ concentration.In order to verify signal transduction pathway of PM H+-ATPase participated stomatal opening, apertures of stomata and cytosolic Ca2+ concentration in guard cells was inveatigated by using epidermal strip as material. Results showed that agonist of H+-ATPase (fusicoccin, FC) lead stomatal opening. Ca2+ permeable channel in plasma membrane which was sensitive to nifedipine may be possibly involved in FC induced stomatal opening. K+ channels in plasma membrane was also involved in FC induced stomatal opening. Cytosolic calcium concentration increased after FC stimulation, calcium signal may possibly participated in FC induce stomatal movements.Extracellular CaM has various biological functions and its activity is regulated by lots of agents. Increasing of [Ca2+]cyt can be induced by Extracellular CaM. It has been reported that the Ca2+ channel in the plasma membrane is activated by CaM, and then induce Ca2+ efflux. Here, by using NADPH mutant, we demonstrated that ROS is involved in Extracellular CaM (ExtCaM) induced stomatal closure. Guard cell outward rectifying K+ channel GORK is also involved in Extracellular CaM induced stomatal closing.
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