Diao, Haoyu, Cernusak, Lucas A., Saurer, Matthias, Gessler, Arthur, Siegwolf, Rolf, and Lehmann, Marco m. (2024) Dry inside: progressive unsaturation within leaves with increasing vapour pressure deficit affects estimation of key leaf gas exchange parameters. New Phytologist, 244 (4). pp. 1275-1287.

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Abstract

Climate change not only leads to higher air temperatures but also increases the vapour pressure deficit (VPD) of the air. Understanding the direct effect of VPD on leaf gas exchange is crucial for precise modelling of stomatal functioning.

We conducted combined leaf gas exchange and online isotope discrimination measurements on four common European tree species across a VPD range of 0.8–3.6 kPa, while maintaining constant temperatures without soil water limitation. In addition to applying the standard assumption of saturated vapour pressure inside leaves (ei), we inferred ei from oxygen isotope discrimination of CO2 and water vapour.

ei desaturated progressively with increasing VPD, consistently across species, resulting in an intercellular relative humidity as low as 0.73 ± 0.11 at the highest tested VPD. Assuming saturation of ei overestimated the extent of reductions in stomatal conductance and CO2 mole fraction inside leaves in response to increasing VPD compared with calculations that accounted for unsaturation. In addition, a significant decrease in mesophyll conductance with increasing VPD only occurred when the unsaturation of ei was considered.

We suggest that the possibility of unsaturated ei should not be overlooked in measurements related to leaf gas exchange and in stomatal models, especially at high VPD.

Item ID:	85407
Item Type:	Article (Research - C1)
ISSN:	1469-8137
Copyright Information:	© 2024 The Author(s). New Phytologist © 2024 New Phytologist Foundation. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
Funders:	Australian Research Council (ARC)
Projects and Grants:	ARC DP210103186
Date Deposited:	08 May 2025 02:11
FoR Codes:	31 BIOLOGICAL SCIENCES > 3108 Plant biology > 310899 Plant biology not elsewhere classified @ 100%
SEO Codes:	28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280102 Expanding knowledge in the biological sciences @ 40% 19 ENVIRONMENTAL POLICY, CLIMATE CHANGE AND NATURAL HAZARDS > 1905 Understanding climate change > 190599 Understanding climate change not elsewhere classified @ 60%
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