Nocturnal stomatal conductance responses to rising [CO2], temperature and drought

• Published in: The New phytologist 2012-03, Vol.193 (4), p.929-938
• Main Authors: Zeppel, Melanie J. B., Lewis, James D., Chaszar, Brian, Smith, Renee A., Medlyn, Belinda E., Huxman, Travis E., Tissue, David T.
• Format: Article
• Language: English
• Subjects: Ambient temperature; Atmospheric models; Carbon Dioxide; Climate; Conductance; Drought; drought mortality; Droughts; Ecosystem; elevated CO2; elevated temperature; Environment; Eucalyptus; Eucalyptus - physiology; Eucalyptus sideroxylon; Fluxes; Herbivores; Leaf area; Moisture content; night‐time stomatal conductance; nocturnal fluxes; Plant Stomata - physiology; Plants; Prediction models; pre‐industrial CO2; Resistance; Soil; Soil temperature regimes; Soil water; Soil water potential; Stomata; Stomatal conductance; Temperature; Tree physiology; Water; Water consumption; Water loss; Water potential; Water resources; Water temperature
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/j.1469-8137.2011.03993.x

The response of nocturnal stomatal conductance (g s,n) to rising atmospheric CO2 concentration ([CO2]) is currently unknown, and may differ from responses of daytime stomatal conductance (g s,d). Because night-time water fluxes can have a significant impact on landscape water budgets, an understanding of the effects of [CO2] and temperature on g s,n is crucial for predicting water fluxes under future climates. Here, we examined the effects of [CO2] (280, 400 and 640 μmol mol−1), temperature (ambient and ambient + 4°C) and drought on g s,n, and g s,d in Eucalyptus sideroxylon saplings. g s,n was substantially higher than zero, averaging 34% of g s,d. Before the onset of drought, g s,n increased by 85% when [CO2] increased from 280 to 640 μmol mol−1, averaged across both temperature treatments. g s,n declined with drought, but an increase in [CO2] slowed this decline. Consequently, the soil water potential at which g s,n was zero (Ψ0) was significantly more negative in elevated [CO2] and temperature treatments. g s,d showed inconsistent responses to [CO2] and temperature. g s,n may be higher in future climates, potentially increasing nocturnal water loss and susceptibility to drought, but cannot be predicted easily from g s,d. Therefore, predictive models using stomatal conductance must account for both g s,n and g s,d when estimating ecosystem water fluxes.