Applications to the EnvEast Doctoral Training Partnership are now closed.
Below you can browse some of the PhD projects we have previously funded; if you would like to be informed when applications open, or if you have any questions about EnvEast and our application process, please email us.
Projects previously funded by EnvEast
Stomatal-based systems analysis of water use efficiency (CASE award with Forest Research)
Dr Tracy Lawson
School of Biological Sciences, University of Essex
Stomata are pores that provide the major route for gaseous exchange across the impermeable cuticle of leaves and stems (Hetherington & Woodward 2003). They open and close to balance the requirement for CO2 entry for photosynthesis against the need to maintain leaf hydration by reducing transpiration of water vapour. Stomata exert major controls on the water and carbon cycles of the world and can limit photosynthetic rates by 50% or more when demand exceeds water supply. Significant reductions in the efficiency of water use (WUE) by plants (=carbon fixed in photosynthesis/water transpired) is thought to arise because stomatal response is slow compared to photosynthesis in the face of environmental fluctuations, especially light. Improving water use efficiency should be possible without a cost to carbon assimilated if the speed of stomatal responsiveness can be enhanced (Lawson et al, 2011; 2012).
Plants including trees are subjected to fluctuating environmental conditions, for example light changes on a time scale of seconds to minutes, due to cloud cover or self-shading from leaves higher up in the canopy. Both photosynthesis and stomata respond to these changes in light and this results in lags in stomatal behaviour that could permit more water loss than is necessary (relative to carbon gain) when light is reduced, or lags that limit carbon assimilation when sun flecks provide more light than the plant can utilise due to restricted stomatal conductance and therefore CO2 influx. These spatial and temporal dynamics in CO2 and H2O fluxes, when scaled up, have important implication not only for plant water use efficiency but for carbon sequestration and local hydrological scenarios.
This project will aim to establish and validate assimilation and WUE at leaf and whole-plant levels, by assessing leaf stomatal responses and kinetics in native woodland trees to short-term fluctuations in light, humidity and CO2 concentration. Scaled canopy level gas exchange measurements will be undertaken using eddy covariance and sap flow techniques that will examine day to day changes in canopy sink strength & evaporative demand. This work will contribute directly to extending the capacity of existing canopy models providing a scaled gas exchange model that will incorporate impacts of climate change on dynamic processes. This will facilitate predictions of transpiration, carbon sequestration and WUE with the incorporation of CO2 uptake & transpiration dynamics in order to provide data on the essential local carbon and hydrological fluxes.
- Start date 1 October 2014