Our Methods
Leaf Gas Exchange
Measuring leaf gas exchange is a key technique in plant physiology that allows us to quantify how plants take up carbon dioxide (CO₂) for photosynthesis and lose water through transpiration. This is done using gas exchange systems equipped with Infrared Gas Analysers (IRGAs), which measure CO₂ and water vapour concentrations in air before and after it passes over a leaf enclosed in a chamber. By analysing these changes, we can determine photosynthetic rates, stomatal conductance, and water-use efficiency. In our lab, we use these measurements to investigate photosynthetic limitations, mesophyll conductance, and plant responses to environmental conditions, helping us improve our understanding of plant function and adaptation.
CO₂ Isotopic Discrimination
The isotopic composition of CO₂ provides a powerful tool for investigating photosynthesis beyond traditional gas exchange measurements. This technique takes advantage of the fact that Rubisco, the enzyme responsible for carbon fixation, discriminates against CO₂ molecules containing heavier isotopes, such as ¹³C and ¹⁸O. By measuring the relative abundance of these isotopes in CO₂, we can gain deeper insights into photosynthetic processes, particularly the movement of CO₂ within the leaf—known as mesophyll conductance (gₘ). In our lab, we use this approach to quantify how efficiently CO₂ diffuses from the intercellular airspaces to the sites of carboxylation in the chloroplasts, helping us refine models of photosynthesis and better understand limitations to carbon assimilation.
Isotopic Fractionation of Transpired Water
The stable isotopic composition of water vapour provides valuable insights into leaf water dynamics and photosynthetic processes. As water moves through the leaf, fractionation occurs due to differences in the diffusion rates of heavy isotopes (¹⁸O and ²H), influencing the isotopic signature of transpired water. In plant physiology, this technique is particularly useful for studying mesophyll conductance to CO₂ in C₄ plants, where it helps determine how efficiently CO₂ reaches the sites of carboxylation. Additionally, it allows us to explore leaf internal water pools, transpiration pathways, and how different photosynthetic types regulate water and carbon fluxes. In our lab, we use this approach to refine models of water-use efficiency and improve our understanding of physiological adaptations to environmental stress.
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