Sap Flow and Gas Exchange in Real and Artificial Plants

Orateur : Kaare H. JENSEN (Department of Physics, Technical University of Denmark)

The exchange of water for atmospheric CO2 to synthesize sugars in plant leaves is the most fundamental currency of terrestrial life. This exchange occurs via epidermal pores—stomata—that balance the leaf’s need to perform photosynthesis against the dangers of desiccation. Gas fluxes and plant productivity depend on external factors such as light, water, and CO2 availability and on geometric properties of the stomata pores. The link between stomata geometry and environmental factors have informed a wide range of scientific fields - from agriculture to climate science, where observed variations in stomata size and density is used to infer prehistoric atmospheric CO2 content. However, the physical mechanisms and design principles responsible for major trends in stomatal patterning, are not well understood. Here we use a combination of biomimetic experiments and theory to rationalize the observed changes in stomatal geometry. We show that the observed correlations between stomatal size and density are consistent with the hypothesis that plants favor efficient use of space and maximum control of dynamic gas conductivity, and – surprisingly - that the capacity for gas exchange in plants has remained constant over at least the last 325 million years. Our analysis provides a new measure to gauge the relative performance of species based on their stomatal characteristics, and suggests efficient designs for micro engineered systems for gas exchange.

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