Determining stomatal response to vapour pressure deficit from gas exchange measurements: conceptual and methodological challenges
Researcher:
Ferrio Díaz, Juan Pedro
Congress:
XVI Simposio Internacional Hispano-Portugués de Relaciones Hídricas en Plantas
Participation type:
Comunicación oral
Other authors:
Ferrio JP. (speaker), Peguero-Pina JJ., Sancho-Knapik D., Gil-Pelegrín E., López-Ballesteros A., Nadal M., Gil-Pelegrín E.
Year:
2024
Location:
Zaragoza
Publication:
Ferrio JP. (speaker), Peguero-Pina JJ., Sancho-Knapik D., Gil-Pelegrín E., López-Ballesteros A., Nadal M., Gil-Pelegrín E. "Determining stomatal response to vapour pressure deficit from gas exchange measurements: conceptual and methodological challenges". XVI Simposio Internacional Hispano-Portugués de Relaciones Hídricas en Plantas. 14-16 Feb 2024.
The worldwide increase in air temperature implies an exponential increase in atmospheric vapour pressure deficit (VPD). Plants typically respond to increasing VPD with a decrease in stomatal conductance (gs) at a pace that varies with the water-use strategy of each species. Inferring these responses from field-based measurements is complex due the interaction of VPD with multiple factors, such as soil water content or light. Besides, the physiological response is driven by the leaf-to-air VPD (VPDleaf), which depends not only on atmospheric VPD, but also on leaf temperature. Alternatively, manipulative experiments using gas exchange devices represent a simple approach to isolate the response of stomatal conductance (gs) to VPDleaf from other environmental variables, but these face some methodological limitations. Firstly, the conditions inside the leaf cuvette are modulated by the leaf, with transpiration partially compensating for the increase in VPD. Secondly, the conditions in the cuvette cannot replicate open-air conditions, mainly through the effect of light quality (short-wave/long-wave ratio) and boundary layer on leaf temperature. In this work, we built empirical models of stomatal response to VPDleaf in a selection of oak species with contrasting water-use response and leaf shape. These models were used in combination with leaf energy-balance models to assess the response of VPDleaf and gs to varying conditions in the cuvette (flow, PAR, temperature, humidity) and in the input reference air (temperature, humidity). This will allow to define the optimal set-up to achieve a wide range of VPDleaf for different species. We also compared the VPDleaf response to the same range of air temperatures and humidity under cuvette and open-air conditions, to assess to what extent the differences in radiation and leaf boundary layer modify the expected plant response.
The worldwide increase in air temperature implies an exponential increase in atmospheric vapour pressure deficit (VPD). Plants typically respond to increasing VPD with a decrease in stomatal conductance (gs) at a pace that varies with the water-use strategy of each species. Inferring these responses from field-based measurements is complex due the interaction of VPD with multiple factors, such as soil water content or light. Besides, the physiological response is driven by the leaf-to-air VPD (VPDleaf), which depends not only on atmospheric VPD, but also on leaf temperature. Alternatively, manipulative experiments using gas exchange devices represent a simple approach to isolate the response of stomatal conductance (gs) to VPDleaf from other environmental variables, but these face some methodological limitations. Firstly, the conditions inside the leaf cuvette are modulated by the leaf, with transpiration partially compensating for the increase in VPD. Secondly, the conditions in the cuvette cannot replicate open-air conditions, mainly through the effect of light quality (short-wave/long-wave ratio) and boundary layer on leaf temperature. In this work, we built empirical models of stomatal response to VPDleaf in a selection of oak species with contrasting water-use response and leaf shape. These models were used in combination with leaf energy-balance models to assess the response of VPDleaf and gs to varying conditions in the cuvette (flow, PAR, temperature, humidity) and in the input reference air (temperature, humidity). This will allow to define the optimal set-up to achieve a wide range of VPDleaf for different species. We also compared the VPDleaf response to the same range of air temperatures and humidity under cuvette and open-air conditions, to assess to what extent the differences in radiation and leaf boundary layer modify the expected plant response.