Fc Induced Stomatal Opening Up And Defend The Cell H <sub> 2 </ Sub> The O <sub> 2 </ Sub> Relations Research

Previous studies have shown that fusicuccin(FC) can promote transpiration, seed germination, cell elongation, the development of coleoptile and leaf generation. FC can also induce cell program death. Moreover, studies shows that darkness- and ABA-inducd stomatal closure were mediated by the increase of H₂O₂ in guard cell, FC promote stomatal open by activating plasma membrane H⁺-ATPase. However, the relationship between FC-induced stomatal open and the change of H₂O₂ level in guard cell remains unclear. In the present study, the relationship between the change of H₂O₂ levels in guard cells of Vicia faba and FC-induced stomatal open and the action mechanism of FC were investigated by means of laser scanning confocal microscopy technique and the epidermal strip bioassay.The main results are as followed:1. Epidermal strips were treated with FC, ASA (an important reducing substrate for H₂O₂ removal), DPI(an inhibitor of the H₂O₂-generating enzyme NADPH oxidase) in darkness for 3h, we found that like ASA and DPI, FC induce stomatal open, indicate that FC-induced stomatal open is related to the decrease of H₂O₂ level in guard cell, we used H2DCF-DA, a specific probe for intracellular H₂O₂, to measure H₂O₂ levels directly in guard cells to determine whether or not FC-induced stomatal open is accompanied by a decrease of H₂O₂ levels in darkness. Our results provide evidence that like ASA and DPI, FC reduce H₂O₂ levels in darkness.2. Epidermal strips were treated with exogenous H₂O₂, FC, ASA, DPI, H₂O₂+ FC, H₂O₂+ ASA, H₂O₂+ DPI in light for 3h, we found that exogenous H₂O₂ remarkably induce stomatal closure. Like ASA, FC can reverse exogenous H₂O₂-induced stomatal closure, but DPI couldn't. The results suggest that FC can abolished H₂O₂ in guard cell we used H₂DCF-DA, a specific probe for intracellular H₂O₂, to further clarify whether FC can affect exogenous H₂O₂-induced DCF fluorescence. Our results showed that FC can scavenge H₂O₂.3. Epidermal strips were treated in darkness alone for 3h, then these epidermal strips were treated with FC, ASA, DPI in darkness for another 1, 3h, we found that darkness remarkably induced the stomatal closure. Like ASA, FC can reopen the stomata that had been closed in darkness, but DPI couldn't. The results suggest that FC can abolished H₂O₂ in guard cell, so reopened the stomata that had been closed in darkness. The effects of FC on the levels of H₂O₂ generated in guard cells held in the dark were also measured. The results showed that FC can scavenge H₂O₂.Taken together our results indicate that FC probably reduce the levels of H₂O₂ in guard cells by scavenging, inducing stomatal open in darkness.