The ascent of water in tall trees has fascinated scientists for over 130 years. However, the microscopic state and dynamic behavior of water within natural and undisturbed trees remain unknown. Here, we employ low-field nuclear magnetic resonance (NMR) to monitor the distribution and movement of water within a living tree in situ, uncovering a counterintuitive water transport process. The hierarchical walls of xylem vessels serve as the primary channels for continuous ascent of water, while the xylem vessels function more like a temporary water reservoir. The helical nanofibers within the vessel walls, which consist of series-wound crystalline and amorphous regions, create a helical Venturi molecular pump structure that efficiently draws water from the xylem vessel reservoir. Importantly, these helical nanofibers possess a semi-disordered surface embedded with a layer of solid-state water akin to a layer of ice. This self-lubricating layer of ice-like monolayer water, combined with the new “ground level” created by the helical arrangement of nanofibers, enables virtually frictionless long-distance transport of water under low negative pressure. Our findings challenge existing theories and offer valuable insights for developing biomimetic fiber pumps characterized by high efficiency and low energy consumption in fluid transportation.

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中文翻译：

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分层螺旋分子泵实现树木中近乎无摩擦的长距离水输送

130多年来，水从高大的树木中上升一直让科学家们着迷。然而，自然和未受干扰的树木中水的微观状态和动态行为仍然未知。在这里，我们采用低场核磁共振（NMR）来监测活树内水的分布和运动，揭示了违反直觉的水传输过程。木质部导管的分层壁是水持续上升的主要通道，而木质部导管的功能更像是临时水库。容器壁内的螺旋纳米纤维由串联的结晶和非晶区域组成，形成螺旋文丘里分子泵结构，可以有效地从木质部容器水库中吸取水。重要的是，这些螺旋纳米纤维具有半无序的表面，嵌入一层类似于冰层的固态水。这种冰状单层水的自润滑层与纳米纤维螺旋排列形成的新“地面”相结合，可以在低负压下实现几乎无摩擦的长距离水输送。我们的研究结果挑战了现有理论，并为开发在流体输送中具有高效率和低能耗的仿生纤维泵提供了宝贵的见解。

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