Nerea Ubierna

  • Nov 7, 2019

Date & Location: November 7, 2019, at 10a; Room 247 Plant Biology Building

Subject: Using stable isotopes to study plant biological processes

Host: Berkley Walker

Abstract:Stable isotopes are a powerful tool used to investigate photosynthetic processes and their response to environmental gradients. The abundance of stable isotopes for C, O and H in plant material is modulated both by plant metabolism and environmental drivers. While other techniques are also available to study plant metabolism, stable isotopes have the unique feature of integrating responses over time and space. Therefore, they can be used to understand biochemical processes from the leaf to the ecosystem level and across temporal scales.

In this talk, I cover the basics of stable isotope theory and present selected examples of applications from the leaf to the tree level. These include: (1) double isotope tracing to investigate the effect of sap-flow and soil CO2 on stem respiration; (2) using C and O stable isotopes to infer leakiness and mesophyll conductance, two key parameters of C4 photosynthesis; (3) unsaturation of vapor pressure inside leaves of C3 species.

The first experiment enhances our understanding of stem CO2 signals, which is required to interpret ecosystem C balances. The second example focusses on C4 plants, which include some of the most productive crops and biofuel species. In this case, stable isotopes were used to describe the efficiency of the photosynthetic process. Finally, the third example evaluates one of the key assumptions of gas exchange theory that leaf internal air is saturated with water vapor. Unsaturation results in underestimation of stomata conductance and CO2 concentration inside the leaf intercellular spaces, which can compromise the interpretation of these widely used parameters. These examples illustrate how stable isotopes are a unique tool to investigate cutting-edge questions in plant physiology and ecology.