Effects of foliar water uptake on embolism in excised Avicennia marina twigs

The presence and propagation of gas within the xylem conduits, embolism, is widely documented in plants. Embolism occurs in response to dehydration or freezing and thawing, yet the mechanisms that enable plants to recover from embolism remain unclear. Foliar water uptake (FWU) may provide plants with access to water that could enable embolism refilling. Building on previous research that showed that FWU could restore leaf hydraulic conductance in Avicennia marina, this study aimed to test if embolism refilling was involved in leaf hydraulic recovery. Four dehydrated twigs from Avicennia marina (with water potential c. -4 MPa) were imaged using lab-based microCT at the dehydrated state, revealing the presence of stem and leaf emboli which were attributed to dehydration and cutting. Following tap water provision to the twig surface, twigs were imaged in periods of c. 4 h to track the rehydration and refilling process. MicroCT imaging revealed a c. 80% decrease in the leaf embolised area within 29 ± 10 h of wetting. Results revealed no change in embolism diameter following FWU, indicating that capillarity was not the main mechanism for refilling. This research suggests that Avicennia marina may be able to recover from embolism by absorption of foliar water. Full details are available at Fuenzalida, T.I., Blacker, M.J., Turner, M., Sheppard, A. and Ball, M.C. (2023), Foliar water uptake enables embolism removal in excised twigs of Avicennia marina. New Phytol, 237: 1136-1145. https://doi.org/10.1111/nph.18613. This research was funded by the Australian Research Council through grant DP180102969: Top-down rehydration: the role of multiple water sources in maintaining hydraulic function of mangroves along gradients in salinity and aridity.

植物木质部导管（xylem conduits）内气体的存在与扩散过程——栓塞（embolism），已在众多植物中被广泛报道。栓塞通常由脱水或冻融循环诱发，但植物从栓塞状态中恢复的具体机制仍不明晰。叶片吸水（foliar water uptake, FWU）或许能为植物提供可用于栓塞修复的水分来源。本研究立足于此前关于叶片吸水可恢复白骨壤（Avicennia marina）叶片导水率的研究成果，旨在验证栓塞修复是否参与了叶片导水功能的恢复过程。

本研究对4份脱水状态的白骨壤细枝（水势约为-4 MPa）进行实验室显微CT（microCT）成像，于脱水状态下扫描发现了茎与叶片中的栓塞，这些栓塞由脱水及剪切操作诱发。在细枝表面施加自来水后，研究人员每隔约4小时进行一次扫描，以追踪其复水与栓塞修复过程。显微CT成像结果显示，在补水后的29±10小时内，叶片的栓塞面积减少了约80%。实验结果表明，叶片吸水后栓塞的直径未发生变化，这说明毛细作用并非栓塞修复的主要机制。本研究表明，白骨壤或许可通过叶片吸水的方式从栓塞状态中恢复。

详细研究内容可参阅以下文献：Fuenzalida, T.I., Blacker, M.J., Turner, M., Sheppard, A. 及 Ball, M.C.（2023）. 叶片吸水可清除离体白骨壤细枝中的栓塞. 《新植物学家（New Phytol）》, 237: 1136-1145. https://doi.org/10.1111/nph.18613.

本研究由澳大利亚研究理事会（Australian Research Council）通过项目编号DP180102969资助，项目名称为：自上而下复水：多水源在维持盐度与干旱梯度下红树林的导水功能中的作用。