The Role Of NO And H₂O₂ In The Indirect Of UV-B Radiation Stomatal Movement Of Vicia Faba Leaves And ABA-inhibition Stomata Opening

A large body of evidence has established that nitric oxide (NO) and hydrogen peroxide (H₂O₂) function as signaling molecules mediates reponses to abiotic and biotic stress, which regulated many process of development, physiology and metabolism in plant. Unique morphology character and physiology action of guard cell make it unique signal transduction tool that provide an elegant system to dissect an intricate network of signaling pathways, so there are increasingly concerns about NO and H₂O₂ is involved in signaling transduction of stomatal movement. Enhancement of UV-B radiation is one of environmental problem, which is drew great attention recently. UV-B radiation has direct and indirect effect on stomatal movement. Our previous experiment has established that both NO and H₂O₂ are involved in the direct effect of UV-B radiation-induced stomatal closure.but it is still unclear whether NO and H₂O₂ mediated the indirect effect of UV-B-induced stomatal closure. It is well known that ABA is one of the most studied phytohormones due to its key participation in different physiological events in plant. ABA can inhibit the stomatal opening, additionally induced stomata closure. Recently, there are a large body of reports about mechanism of ABA-induced stomatal closure, moreover it has established that NO and H₂O₂ function as signaling molecular in the ABA-induced stomatal closure. But there is little information available whether NO and H₂O₂ also mediate ABA inhibition of stomata opening. The present experiments, using intact leaves of vicia faba L., epidermal strip bioassay, laser-scanning confocal microscopy and portable photosynthesis system, we investigate the role of NO and H₂O₂ in the indirect effects of UV-B radiation on stomatal movement of vicia faba L. and ABA inhibition of stomata opening. The main results are as follows:The results showed that when the fourth leaf pair of broad bean (Vicia faba) plants was suddenly exposed to 0.2 W·m^-2 UV-B radiation, not only the stomata conductance and aperture were reduced significantly, but also the mesophyll photosynthetic activity were decreased. However, when the isolated epidermal strips were exposed to the same dose of UV-B radiation, the stomata movement was not affected. These results indicated that 0.2 W·m^-2 UV-B radiation regulated stomatal movement of intact leaves through an...