School of Biology and Environmental Sciences, University College Dublin (UCD), Belfield, Dublin 4, Ireland.
New Phytol. 2020 Feb;225(3):1152-1165. doi: 10.1111/nph.15773. Epub 2019 Mar 30.
Plants grow and transpire during the night. The aim of the present work was to assess the relative flows of carbon, water and solutes, and the energy involved, in sustaining night-time transpiration and leaf expansive growth under control and salt-stress conditions. Published and unpublished data were used, for barley plants grown in presence of 0.5-1 mM NaCl (control) and 100 mM NaCl. Night-time leaf growth presents a more efficient use of taken-up water compared with day-time growth. This efficiency increases several-fold with salt stress. Night-time transpiration cannot be supported entirely through osmotically driven uptake of water through roots under salt stress. Using a simple three- (root medium/cytosol/vacuole) compartment approach, the energy required to support cell expansion during the night is in the lower percentage region (0.03-5.5%) of the energy available through respiration, under both, control and salt-stress conditions. Use of organic (e.g. hexose equivalents) rather than inorganic (e.g. Na , Cl , K ) solutes for generation of osmotic pressure in growing cells, increases the energy demand by orders of magnitude, yet requires only a small portion of carbon assimilated during the day. Night-time transpiration and leaf expansive growth should be considered as a potential acclimation mechanism to salinity.
植物在夜间生长和蒸腾。本研究旨在评估在控制和盐胁迫条件下，维持夜间蒸腾和叶片扩展生长所涉及的碳、水和溶质的相对流动以及能量。使用了已发表和未发表的数据，研究对象为在 0.5-1mM NaCl（对照）和 100mM NaCl 存在下生长的大麦植株。与白天生长相比，夜间叶片生长能更有效地利用吸收的水分。这种效率在盐胁迫下增加了几倍。在盐胁迫下，夜间蒸腾不能完全通过根的渗透驱动来吸收水分来维持。使用一个简单的三（根介质/细胞质/液泡）隔室方法，在控制和盐胁迫条件下，支持夜间细胞扩展所需的能量占呼吸作用提供的能量的较低百分比区域（0.03-5.5%）。利用有机（例如己糖当量）而不是无机（例如 Na+、Cl-、K+）溶质来产生生长细胞中的渗透压力，会使能量需求增加几个数量级，但仅需要白天同化的一小部分碳。夜间蒸腾和叶片扩展生长应该被视为一种对盐度的潜在适应机制。
