Towards understanding stomatal decoupling under extreme heat: integrating stomatal kinetics, leaf light responses, and the role of stomatal versus cuticular conductance

Stomatal decoupling at high leaf temperature occurred in two of four tree species, including the most anisohydric species, but not in a vulnerable rainforest species.

• Why it matters: Hotter drought events are linked to unprecedented forest dieback, yet the mechanisms and species variability behind stomatal decoupling at high Tleaf remain unclear.
• What they did: In a glasshouse experiment, heat and drought stress were imposed on two rainforest and two semi-arid tree species while measuring thermal and hydraulic balance, plus light- and dark-driven stomatal kinetics at 25°C versus 34°C.
• The result: Accelerated leaf water loss occurred mainly through open stomata rather than the cuticle, and at 34°C light-induced opening was up to two times faster while dark-induced closing was 14 minutes slower on average.