The mechanism of SO2-induced stomatal closure differs from O3 and CO2 responses and is mediated by non-apoptotic cell death in guard cells ($) (Plant Cell Environ)

Stomata opening and closing are regulated by guard cells. Airborne pollutants such as ozone, sulfur dioxide, and nitrogen dioxide cause stomatal closure. In this study, Lia Ooi et al. tried to understand the molecular mechanism of SO2-induced stomatal closure. SO2 is found in three forms in aqueous solution (H2CO3, HSO3, SO32-) and the authors showed that H2SO3 is responsible for the stomata closure. Interestingly, SO2 induces stomata closure using a different molecular mechanism than that used by O3 and CO2. The authors demonstrated that SO2-induced stomatal closure correlates with non-apoptotic cell death in guard cells. This study reveals a unique stress avoidance response of stomata against SO2 gas. (Summary by Arif Ashraf) Plant Cell Environ. 10.1111/pce.13406