School of Biology and Environmental Sciences, University College Dublin, Dublin, Republic of Ireland.
Physiol Plant. 2023 Jan;175(1):e13839. doi: 10.1111/ppl.13839.
The study aimed to test whether night-time transpiration provides any potential benefit to wheat plants which are subjected to salt stress. Hydroponically grown wheat plants were grown at four levels of salt stress (50, 100, 150, and 200 mM NaCl) for 5-8 days prior to harvest (day 14-18). Salt stress caused large decreases in transpiration and leaf elongation rates during day and night. The quantitative relation between the diurnal use of water for transpiration and leaf growth was comparatively little affected by salt. Night-time transpirational water loss occurred predominantly through stomata in support of respiration. Diurnal gas exchange and leaf growth were functionally linked to each other through the provision of resources (carbon, energy) and an increase in leaf surface area. Diurnal rates of water use associated with leaf cell expansive growth were highly correlated with the water potential of the xylem, which was dominated by the tension component. The tissue-specific expression level of nine candidate aquaporin genes in elongating and mature leaf tissue was little affected by salt stress or day/night changes. Growing plants under conditions of reduced night-time transpirational water loss by increasing the relative humidity (RH) during the night to 95% had little effect on the growth response to salt stress, nor was the accumulation of Na and Cl in shoot tissue altered. We conclude that night-time gas exchange supports the growth in leaf area over a 24 h day/night period. Night-time transpirational water loss neither decreases nor increases the tolerance to salt stress in wheat.
该研究旨在测试夜间蒸腾是否会给处于盐胁迫下的小麦植株带来任何潜在益处。水培小麦植株在收获前（第 14-18 天）经历 5-8 天的 4 个盐胁迫水平（50、100、150 和 200 mM NaCl）。盐胁迫导致白天和夜间的蒸腾和叶片伸长率大幅下降。白天和夜间蒸腾作用的用水量与叶片生长之间的定量关系受盐的影响较小。夜间蒸腾失水主要通过支持呼吸的气孔发生。白天的气体交换和叶片生长通过提供资源（碳、能量）和增加叶片表面积而彼此紧密相连。与叶片细胞扩展生长相关的白天水的使用速率与木质部的水势高度相关，木质部的水势主要由张力成分主导。在盐胁迫或昼夜变化下，伸长和成熟叶片组织中 9 个候选水通道蛋白基因的组织特异性表达水平受影响较小。通过在夜间将相对湿度（RH）提高到 95%来减少夜间蒸腾失水，对盐胁迫生长反应几乎没有影响，也不会改变茎组织中 Na 和 Cl 的积累。我们得出结论，夜间气体交换支持 24 小时昼夜周期内叶片面积的增长。夜间蒸腾失水既不会降低也不会增加小麦对盐胁迫的耐受性。
