Both seminars will be held on Tuesday, November 21, 1:20 – 3:00 pm, 404 Plant Science Building
https://cornell.zoom.us/j/99986531869?pwd=SEZYRk9QeDJBRm1PbXY1L0VWMm5WZz09
Meeting ID: 999 8653 1869
Passcode: 810284
Title: Understanding leaf-level CO2 diffusion: A necessity for improving global Gross Primary Productivity (GPP) estimates
Speaker: Dr. Florian Busch (School of Biosciences – University of Birmingham, UK)
Abstract: Estimations of the gross primary productivity (GPP) of land ecosystems are key to accurately predict the global carbon cycle. The photosynthesis models underpinning these estimates are making simplifications that result in GPP inaccuracies in the order of 10-15% by the end of the century (Knauer et al., 2019). These simplifications have been necessary due to insufficient understanding of how CO2 is taken up by the leaf. Carbon isotopes are commonly used to study how CO2 diffuses within photosynthetic plant tissues, information that is difficult to obtain with common gas exchange techniques alone. The standard method used to interpret the observed preference for the lighter carbon isotope in C3 photosynthesis involves the model of Farquhar et al. (1982), which relates carbon isotope discrimination to physical and biochemical processes within the leaf. However, under many conditions the model returns unreasonable results for mesophyll conductance to CO2 diffusion, including values that are negative. Here, I will discuss the impact of a re-derived carbon isotope discrimination model on quantifying mesophyll conductance and the implications this has for predictions of plant carbon uptake. This new model allows us now to assess how mesophyll conductance varies under changing environments. I will also outline a new theoretical framework that can be used to mechanistically implement mesophyll conductance into photosynthesis models, giving us the opportunity to vastly improve global GPP estimates.
Bio: Florian Busch (University of Birmingham) is a theoretical and experimental plant physiologist interested in all aspects of photosynthesis. His focus is on linking different photosynthetic processes with mathematical models to study the biochemical limitations of carbon fixation and to gain a quantitative understanding of how plant carbon uptake responds to changes in the environment. Florian obtained his PhD in 2008 from the Heinrich-Heine University in Düsseldorf, Germany, during which time he worked closely with Norm Hüner at Western University in London, Canada. After several years of post-doctoral work with Rowan Sage at the University of Toronto, Canada he moved to the Australian National University to first work as a Postdoctoral Fellow with Susanne von Caemmerer and later as a Research Fellow with Graham Farquhar. He is now an Associate Professor in the School of Biosciences at the University of Birmingham.
Title: Mesophyll air space unsaturation: Vapour gradients and cell membrane hydraulic conductivity
Speaker: Dr. Diego Marquez (School of Biosciences – University of Birmingham, UK)
Abstract: Unravelling the CO2 and water dynamics within the leaf is pivotal for accurately defining leaf gas exchange behaviour, which is essential in scientific research and crop improvement efforts. Recent evidence has refuted the longstanding assumption that leaf air spaces remain saturated, revealing gaps in our understanding of gas exchange processes under diverse conditions such as drought and high atmospheric vapour pressure deficit. We will discuss our recent studies exploring vapour gradients in the leaf intercellular air space. Our findings demonstrate that mesophyll cells can maintain significant water-potential differences between the cytosol and cell wall under high evaporative demand, resulting in pronounced unsaturation in the mesophyll air space and substomatal cavity. This unveils the existence of an important resistance to water movement through the cell membrane and considerable non-stomatal resistance to transpiration, which has not been accounted for.
Bio: Diego Márquez received a Master of Science in Agronomic Engineering from the University of Chile and a PhD in Plant Science from the Australian National University.
He is currently a Research Fellow in the lab of Dr Florian Busch at the University of Birmingham, working on the role of mesophyll CO2 diffusion in photosynthesis and water use efficiency.
Dr Márquez is a Plant Physiologist who combines theoretical biophysics and experimental approaches to develop mechanistic models for gas exchange, carbon fixation, and hydraulic systems in plants. His current research focuses on water and CO2 gradients and resistances to diffusion in the mesophyll’s intercellular air space and liquid volume.