Research Details: Stomatal physiology - Climate change and increasing global population is intensifying the need to find suitable crop plants for sustainable food and fuel production for future generations. Drought conditions and reduced water availability severely impact plant productivity and are considered a global threat to world food security. Stomata and their function therefore play a central role in determining the amount of carbon gained per unit water lost, known as plant “water use efficiency” and consequently have significant implications for crop yields, as well as global hydrological and carbon cycles. Stomata must ensure an appropriate balance between CO2 demands for photosynthesis and water loss through transpiration by correlating stomatal conductance with mesophyll photosynthetic rates. The underlying mechanisms and signals that promote this relationship are currently unknown. Stomata and photosynthesis respond to a number of environmental cues, however responses are not synchronized, with stomatal adjustments generally an order of magnitude slower than mesophyll responses. The resulting disconnection between stomatal conductance and photosynthetic rate means that under natural fluctuating environmental condition water use efficiency is most likely far from optimal. I am therefore interested in stomatal control of CO2 assimilation and the relation between mesophyll photosynthesis and stomatal behaviour and the signalling pathways that link these two fundamental processes. I also research the role of guard cell chloroplasts in stomatal function and how guard cell photosynthesis may provide a functional link between mesophyll photosynthesis and guard cell aperture.
Cyanobacterial physiology - Oceans play a major role in the global carbon cycle, with about 50% of the Earth’s photosynthesis each year occurring in aquatic marine environments, representing a major sink for atmospheric carbon dioxide (CO2). Primary productivity in many areas of the world’s oceans is limited by nitrogen and other nutrients such as phosphorous (P). Thus N2 fixing cyanobacteria including the dominant filamentous Trichodesmium are important in oligotrophic waters where they contribute the N that supports up to 50% of export production (Tyrrell et al., 2003; Capone et al., 2005). N2 fixation is an energy requiring process catalyzed by the enzyme nitrogenase, which is irreversibly damaged by molecular oxygen. Therefore, N2 fixing cyanobacteria must prevent nitrogenase from being damaged by molecular oxygen produced as a by-product of photosynthesis. Most diazotrophic cyanobacteria achieve this by separating photosynthesis and N2 fixation either spatially or temporally. Spatial separation is accomplished by conducting N2 fixation in specialized cells called heterocysts whilst temporal segregation relies on the use of respiratory energy to fix N2 at night. In contrast to these two strategies, the non-heterocyst cyanobacterium Trichodesmium executes both photosynthesis and N2 fixation during the light period without morphological differentiation of specialized cells. I am currently investigating the mechansims that allow photosynthesis and N2 fixation to occur simultaneously. I am also investigating the influence of elevated CO2 and nutrient limitation on photosynthetic processes and N2 fixation in two key cyanobacteria Trichodesmium and Crocosphaera.
Silvère Vialet-Chabrand. Post Doc. Stomatal-based systems analysis of water use efficiency. (BBSRC Standard Grant); in collaboration with M. Blatt (Glassgow) & H.Griffiths (Cambridge). 2014-2017.
Jack Matthews. PhD student. Scaling up dynamic responses of stomata to assess impacts on tree canopy carbon gain and water use efficiency.(NERC Env East DTP studentship). .
Kucheli Batta. PhD student. The role of guard cell chloroplasts in co-ordinating stomatal and mesophyll responses.
Ifeanyi Oyemike. PhD student. Manipulating Guard cell anatomy and physiology using biotechnological approaches to understanding impact on crop performance.
Yazen Al-Salmon. MSc student. Atmosphere-Biosphere co-evolution across geological time: The relationship between atmospheric carbon dioxide concentrations and plant hydraulic capacity.
Jim Stevens. PhD student. Understanding water-use variation in elite barley varieties. (Funded by The Perry Foundation & School of Biological Sciences, University of Essex).
John Stamford. PhD student. Using spectral signatures as a toolbox for determining crop health status. (BBSRC Industrial Case Studentship, with industrial partners Environment Systems Ltd.).
Previously funded project:
· Ocean Acidification impacts on sea-surface biology, biogeochemistry and climate (NERC consortium PhD studentship); Co-Investigator Feb 2011-Jan 2014: PhD student - L. Bretherton
· A community metabolism approach to examine the environmental regulation of coral growth (NERC standard grant); Oct 2009-Sep 2012: Co-I Investigator PDRA - Dr D. Laing.
· Effect of light, CO2 and nutrient limitation on photosynthesis in marine diazotrophic cyanobacteria. (NERC standard grant). March 2008- August 2011. PDRA - Dr. M. Fryer.
· Establishing the mechanism(s) that enable stomata to respond to changing environmental cues, facilitating enhanced water use efficiency. (NERC quota studentship to Department of Biological Sciences). PhD student L. McAusland.