Evidence for a multicellular water pump fueled by symplastic osmotic potential gradients in vascular plant ro
(2021) SEB 2021 Annual Conference — Location: online (29.June.2021)
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Couvreur_Evidence_for_a_multicellular_water_pump.mp4
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- Authors
Heymans, Adrien 
- Abstract
- (en) The current paradigm of root radial water flow assumes that water only flows “downhill” of water potential gradients, so that the only way to pump water without lowering xylem relative pressure is by lowering xylem total water potential through solute loading. However, numerous studies report that crops and woody species roots may absorb water despite higher xylem pressure and lower xylem solute concentration, as compared to the root direct environment (i.e. water would flow “uphill” of water potential gradients). This contradicts the current paradigm of root water acquisition, and seemingly goes against the second law of thermodynamics. We recently found a physiological mechanism solving this enigma with a micro-hydrological model of water flow across roots, called MECHA. Osmotic gradients between living cells generate pressure gradients driving water through plasmodesmata, with a surprising result: subcellular flow “downhill” of local water potential gradients may translate into flow “uphill” of both total and pressure potential gradients between root surface and xylem. This water pumping mechanism means any vascular plant may reduce its xylem water tension and increase its water availability beyond predictions of the current theory. Here, we demonstrate of the water pumping mechanism mathematically by solving water flow equations analytically on a triple-cell system. Then we show that the associated upscaled equations hold in 2- and 3-D maize and Arabidopsis hydraulic anatomies, and that water flows “uphill” of water potential gradients toward xylem as observed experimentally
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Citations
Couvreur, V., Heymans, A., Lobet, G., Bennett, M., & Draye, X. (2021). Evidence for a multicellular water pump fueled by symplastic osmotic potential gradients in vascular plant ro. SEB 2021 Annual Conference, online. https://hdl.handle.net/2078.5/239114