Authors
Schuler, P., Didion-Gency, M., Bortolami, G., Juillard, T., Hoch, G., Bachofen, C., Kahmen, A.
Abstract
Photosynthetic assimilation (Anet) and stomatal conductance (gs) are usually strongly coupled, but this relationship is decreased or even lost at high temperatures (Tair). The contributions of environmental drivers (Tair, vapour pressure deficit (VPD), and soil moisture) in interaction with the physiological mechanisms behind this process are still unclear. We exposed saplings of three temperate and tropical species to rising Tair (20 to 40{degrees}C) at low (1.2 to 1.9 kPa) and increasing VPD (1.1 to 5.6 kPa), and at stable Tair (35{degrees}C) to increasing VPD (1.4 to 4.3 kPa) under well-watered or chronic soil drought conditions (10%). Anet, gs, and transpiration (E) in the light and the dark and leaf thermoregulation were tracked throughout the experiment. When VPD remained low, gs continued to increase while Anet decreased at Tair > 35{degrees}C, leading to stomatal decoupling. In contrast, under rising VPD, trees maintained the coupling between Anet and gs at high Tair. While a decoupling of Anet and gs only occurred when VPD was low, Anet and E decoupled under both VPD regimes at high Tair. Our results indicate that, since gs and VPD collectively drive E, stomatal decoupling is needed to increase E when VPD is not sufficiently high.
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bioRxiv
The authors list and abstract were imported from bioRxiv on 05 Nov 2025.
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