Reduced photosynthetic dark reaction triggered by ABA application increases intercellular CO2 concentration, generates H2O2 and promotes closure of stomata in ginger leaves

Abstract

Exogenous abscisic acid application decreased stomatal conductance (Gs), net photosynthetic rate (Pn), photorespiration rate (Pr), carboxylation efficiency (CE), and actual photochemical efficiency (ΦPSII) but increased the Mehler reaction, antioxidant enzyme activities and H2O2 content in ginger leaves. The observed reopening of the stomata triggered by varying concentrations of external CO2 indicates that increased intercellular CO2 concentration (caused by decreased photosynthetic dark reaction activity) promotes stomatal closure under ABA content regulation. By comparing the relationships between H2O2 content, stomatal conductance and ABA content under well-watered conditions compared to osmotic drought stress conditions, we concluded that increased H2O2 content caused by exogenous ABA application also promoted stomata closure in ginger leaves. Thus, CO2 and H2O2 signalling promote more complete stomatal closure under the influence of ABA in ginger leaves.