Functional characterisation of plant leaf airspaces in 3D

Plant leaves are key components to the global carbon and water cycle, as virtually all terrestrial carbon going from the atmosphere to terrestrial ecosystems and ~70% of all terrestrial transpired water passes through them. Research on carbon and water fluxes at the leaf has primarily focused on how the pores on the surface of the leaf (stomata) and the cells where photosynthesis occurs (mesophyll cells) respond to changes in their environmental conditions. However, there is a space within the leaf that has often been overlooked or ignored when studying photosynthesis as this air-filled cavity barely limits the movement of CO2 in crop plants, which have most often been studied. However, this airspace was shown to limit the movement of CO2 for certain leaf types found over a wide range of environments around the globe. Further, leaves of the flowering plants (angiosperms), the most diversified and recent plant group in terms of evolution, have improved stomatal control and water transport properties compared to their ancestors like ferns and gymnosperms such as conifers. Little is known on the diversity of the leaf airspace properties and whether or not the angiosperms have evolved improved traits similar to those related to water transport. The proposed project “Functional characterisation of plant leaf airspaces in 3D” will try to answer that question. The research, building from state-of-the-art three-dimensional leaf imaging through high resolution X-ray computed tomography, will allow to present the leaf airspace properties in their true volumetric nature. In combination with an in-depth analysis of photosynthesis and transpiration, the 3D representation of the leaf will make it possible to accurately describe the importance of the air space in carbon and water transport processes within the leaf, as well as the coordination of airspace properties with other related leaf traits. For this functional characterization, modelling at a small scale will be done using finite element analysis, a tool mostly used in engineering, that will accurately represent the physical processes within the diverse 3D leaf anatomies acquired. This modelling will be then used to build a leaf model that treats a canopy as a single big leaf in order to quantify the role of the leaf airspace in the plant carbon and water relations. This new knowledge is key to fully understand how leaves evolved, adapted, and optimized carbon acquisition and water loss in response to a changing environment, providing important information to reconstruct fossil leaf properties as well as to improve the prediction of plants responses to future climate.