Harvesting water from unsaturated atmospheres: deliquescence of salt secreted onto leaf surfaces drives reverse sap flow in a dominant arid climate mangrove, Avicennia marina
Harvesting water from unsaturated atmospheres: deliquescence of salt secreted onto leaf surfaces drives reverse sap flow in a dominant arid climate mangrove, Avicennia marina
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DOI：
10.1111/nph.17461
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发表时间：
2021-06-12
期刊：
影响因子：
9.4
通讯作者：
Ball, Marilyn C.
中科院分区：
文献类型：
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作者：
Coopman, Rafael E.;Nguyen, Hoa T.;Ball, Marilyn C.
红树Avicennia marina通过叶面分泌盐分调节内部盐浓度。在干旱的沿海湿地，高夜间湿度通常可以支持潮解，而降雨事件很少，积累的盐的潮解引起叶片湿润，这可能为分泌盐的植物提供水源。我们测试了叶片表面的盐潮解可以驱动自上而下的再水合作用的假设，以及这种从不饱和大气中吸收水分对旱季茎部水分平衡的功能贡献。在自然和人为控制的小气候条件下，通过监测树液流和水分关系来评估茎部湿润过程中树枝对大气水分的吸收。反液流速率随相对湿度的增加而增加，从70%增加到89%，这与盐潮解在不饱和大气中获取水分的作用一致。自上而下的再水化提高了树枝的水势，高于根系吸收水分的水势，降低了蒸腾速率，减少了树枝在随后的光周期中对水力破坏的脆弱性。通过叶片表面盐的潮解吸收大气水分，提高了干旱气候条件下生长在高盐湿地的水平衡。从这些频繁、低强度的湿润事件中自上而下的补水有助于防止干旱期间的碳饥饿和水力衰竭。
The mangrove Avicennia marina adjusts internal salt concentrations by foliar salt secretion. Deliquescence of accumulated salt causes leaf wetting that may provide a water source for salt-secreting plants in arid coastal wetlands where high nocturnal humidity can usually support deliquescence whereas rainfall events are rare. We tested the hypotheses that salt deliquescence on leaf surfaces can drive top-down rehydration, and that such absorption of moisture from unsaturated atmospheres makes a functional contribution to dry season shoot water balances.Sap flow and water relations were monitored to assess the uptake of atmospheric water by branches during shoot wetting events under natural and manipulated microclimatic conditions.Reverse sap flow rates increased with increasing relative humidity from 70% to 89%, consistent with function of salt deliquescence in harvesting moisture from unsaturated atmospheres. Top-down rehydration elevated branch water potentials above those possible from root water uptake, subsidising transpiration rates and reducing branch vulnerability to hydraulic failure in the subsequent photoperiod.Absorption of atmospheric moisture harvested through deliquescence of salt on leaf surfaces enhances water balances of Avicennia marina growing in hypersaline wetlands under arid climatic conditions. Top-down rehydration from these frequent, low intensity wetting events contributes to prevention of carbon starvation and hydraulic failure during drought.