H2O2 mediates ExtCaM-induced V. faba stomatal closure. A, Effect of 5 × 10−5 m H2O2 in MES buffer on stomatal closure within 2 h. Control indicates no addition of H2O2 except MES buffer. B, Effects of DPI or CAT on stomatal closure-induced by CaM for 2 h. Control, Open stomata were kept in MES buffer under light for 2 h, then the stomatal aperture was treated as 100%; CaM, open stomata were treated with 10−8 m CaM solution; CaM + CAT, open stomata were treated with 100 units/mL CAT plus 10−8 m CaM; CaM + DPI, open stomata were kept in 10 μm DPI plus 10−8 m CaM. Each assay was repeated three times. The data were presented as mean ± se (n = 150).