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A biomimetic experiment to understand the drying of leaves

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The resistance of trees to drought is a growing concern in the context of global warming. Under dry conditions, embolisms can appear in the sap network within leaves, potentially stopping the circulation and leading to leaf drying. However, the propagation and growth of embolisms in leaves remains poorly understood.

Researchers from LIPhy have undertaken a physical study to study such embolisms in an artificial leaf, made of initially water-filled channels within a thin layer of a water-permeable material. They reproduced the drying conditions specific to leaves, namely the liquid evaporation from channel to the outer atmosphere by diffusion through the permeable material, and the associated embolism growth. They have understood the role of geometrical parameters such as the channel length and cross-section or the leaf thickness, by quantifying the diffusive dynamics of water through the "bulk" of the leaf. In particular, the water-filled part of a given channel diplays a length L which exponentially decreases until a time t_c at which the channel gets completely dry; the narrower the channel and the thinner the layer of permeable material, the shorter the drying time.

 Drying dynamics of a biomimetic leaf:
Drying dynamics of a biomimetic leaf:
decay of the water-filled part of channels of different widths (the narrower the channel, the faster the decay.