Stomatal closure in sweet potato leaves induced by sulfur dioxide involves H<sub>2</sub>S and NO signaling pathways

Abstract

Sulfur dioxide (SO2) is a well-known and widespread air pollutant but it also acts as signaling molecule in various processes in animals. However, there is limited information on the role of SO2 in plants except of its toxicity. Here we studied the role of SO2 on stomatal movements in sweet potato (Ipomoea batatas) leaves. SO2, generated by Na2SO3/NaHSO3 solutions, was applied on epidermal strips. We found that the SO2 donor induced stomatal closure in a dose-dependent manner. Rapid increases in endogenous hydrogen sulfide and nitric oxide content levels were observed in leaves after the treatment with the SO2 donor. The SO2-induced stomatal closure was reversed by the H2S scavenger hypotaurine and the NO-specific scavenger cPTIO. Our results indicate that the SO2-induced stomatal closure was likely mediated by the H2S and NO signaling pathways.