Stomatal movements are involved in elevated CO₂‐mitigated high temperature stress in tomato

Abstract

Climate changes such as heat waves often affect plant growth and pose a growing threat to natural and agricultural ecosystems. Elevated atmospheric CO 2 can mitigate the negative effects of heat stress, but the underlying mechanisms remain largely unclear. We examined the interactive effects of elevated CO 2 (eCO 2 ) and temperature on the generation of the hydrogen peroxide (H 2 O 2 ) and stomatal movement characteristics associated with heat tolerance in tomato seedlings grown under two CO 2 concentrations (400 and 800 µmol mol −1 ) and two temperatures (25 and 42°C). eCO 2 ameliorated the negative effects of heat stress, which was accompanied by greater amounts of RESPIRATORY BURST OXIDASE 1 ( RBOH1 ) transcripts, apoplastic H 2 O 2 accumulation and decreased stomatal aperture. Silencing RBOH1 and SLOW-TYPE ANION CHANNEL , impeded eCO 2 ‐induced stomatal closure and compromised the eCO 2 ‐enhanced water use efficiency as well as the heat tolerance. Our findings suggest that RBOH1 ‐dependent H 2 O 2 accumulation was involved in the eCO 2 ‐induced stomatal closure, which participate in maintaining balance between water retention and heat loss under eCO 2 concentrations. This phenomenon may be a contributor to eCO 2 ‐induced heat tolerance in tomato, which will be critical for understanding how plants respond to both future climate extremes and changes in CO 2 .