Decoupling between stomatal conductance and photosynthesis occurs under extreme heat in broadleaf tree species regardless of water access

© 2023 The Authors. Global Change Biology published by John Wiley & Sons Ltd.

Bibliographische Detailangaben
Veröffentlicht in:Global change biology. - 1999. - 29(2023), 22 vom: 12. Nov., Seite 6319-6335
1. Verfasser: Marchin, Renée M (VerfasserIn)
Weitere Verfasser: Medlyn, Belinda E, Tjoelker, Mark G, Ellsworth, David S
Format: Online-Aufsatz
Sprache:English
Veröffentlicht: 2023
Zugriff auf das übergeordnete Werk:Global change biology
Schlagworte:Journal Article Australia drought heat tolerance heatwave stomata transpirational cooling urban trees vapor pressure deficit
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520 |a High air temperatures increase atmospheric vapor pressure deficit (VPD) and the severity of drought, threatening forests worldwide. Plants regulate stomata to maximize carbon gain and minimize water loss, resulting in a close coupling between net photosynthesis (Anet ) and stomatal conductance (gs ). However, evidence for decoupling of gs from Anet under extreme heat has been found. Such a response both enhances survival of leaves during heat events but also quickly depletes available water. To understand the prevalence and significance of this decoupling, we measured leaf gas exchange in 26 tree and shrub species growing in the glasshouse or at an urban site in Sydney, Australia on hot days (maximum Tair  > 40°C). We hypothesized that on hot days plants with ample water access would exhibit reduced Anet and use transpirational cooling leading to stomatal decoupling, whereas plants with limited water access would rely on other mechanisms to avoid lethal temperatures. Instead, evidence for stomatal decoupling was found regardless of plant water access. Transpiration of well-watered plants was 23% higher than model predictions during heatwaves, which effectively cooled leaves below air temperature. For hotter, droughted plants, the increase in transpiration during heatwaves was even more pronounced-gs was 77% higher than model predictions. Stomatal decoupling was found for most broadleaf evergreen and broadleaf deciduous species at the urban site, including some wilted trees with limited water access. Decoupling may simply be a passive consequence of the physical effects of high temperature on plant leaves through increased cuticular conductance of water vapor, or stomatal decoupling may be an adaptive response that is actively regulated by stomatal opening under high temperatures. This temperature response is not yet included in any land surface model, suggesting that model predictions of evapotranspiration may be underpredicted at high temperature and high VPD 
650 4 |a Journal Article 
650 4 |a Australia 
650 4 |a drought 
650 4 |a heat tolerance 
650 4 |a heatwave 
650 4 |a stomata 
650 4 |a transpirational cooling 
650 4 |a urban trees 
650 4 |a vapor pressure deficit 
700 1 |a Medlyn, Belinda E  |e verfasserin  |4 aut 
700 1 |a Tjoelker, Mark G  |e verfasserin  |4 aut 
700 1 |a Ellsworth, David S  |e verfasserin  |4 aut 
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773 1 8 |g volume:29  |g year:2023  |g number:22  |g day:12  |g month:11  |g pages:6319-6335 
856 4 0 |u http://dx.doi.org/10.1111/gcb.16929  |3 Volltext 
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