Many tree species have developed extensive root systems that allow them to survive in arid environments by obtaining water from a large soil volume. These root systems can transport and redistribute soil water during drought by hydraulic redistribution (HR). A recent study revealed the phenomenon of evaporation-driven hydraulic redistribution (EDHR), which is driven by evaporative demand (transpiration). In this study, we confirmed the occurrence of EDHR in Chinese white poplar (Populus tomentosa) through root sap flow measurements. We utilized microcomputed tomography technology to reconstruct the xylem network of woody lateral roots and proposed conceptual models to verify EDHR from a physical perspective. Our results indicated that EDHR is driven by the internal water potential gradient within the plant xylem network, which requires 3 conditions: high evaporative demand, soil water potential gradient, and special xylem structure of the root junction. The simulations demonstrated that during periods of extreme drought, EDHR could replenish water to dry roots and improve root water potential up to 38.9% to 41.6%. This highlights the crucial eco-physiological importance of EDHR in drought tolerance. Our proposed models provide insights into the complex structure of root junctions and their impact on water movement, thus enhancing our understanding of the relationship between xylem structure and plant hydraulics.

College of Life and Environmental Science Minzu University of China Beijing 100081 China

Institute of Forest Botany Dendrology and Geobiocenology Mendel University in Brno Zemedelska 3 Brno 61300 Czech Republic

Laboratory for Silviculture and Forest Ecosystem in Arid and Semi Arid Region of State Forestry and Grassland Administration Beijing Forestry University Beijing 10083 China

Ministry of Education Key Laboratory of Silviculture and Conservation Beijing Forestry University Beijing 100083 China

New Zealand Institute for Plant and Food Research Ltd Fitzherbert Science Centre Palmerston North 4442 New Zealand

New Zealand Institute for Plant and Food Research Ltd Private Bag 4707 Christchurch 8140 New Zealand

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