Bordeaux Sciences AGRO, UMR1391 ISPA INRA, 1 Cours du général de Gaulle, 33175 Gradignan Cedex, France.
Nicholas School of the Environment, Duke University, Durham, NC 27708, USA.
J Exp Bot. 2021 May 28;72(12):4489-4501. doi: 10.1093/jxb/erab100.
The influence of aquaporin (AQP) activity on plant water movement remains unclear, especially in plants subject to unfavorable conditions. We applied a multitiered approach at a range of plant scales to (i) characterize the resistances controlling water transport under drought, flooding, and flooding plus salinity conditions; (ii) quantify the respective effects of AQP activity and xylem structure on root (Kroot), stem (Kstem), and leaf (Kleaf) conductances; and (iii) evaluate the impact of AQP-regulated transport capacity on gas exchange. We found that drought, flooding, and flooding plus salinity reduced Kroot and root AQP activity in Pinus taeda, whereas Kroot of the flood-tolerant Taxodium distichum did not decline under flooding. The extent of the AQP control of transport efficiency varied among organs and species, ranging from 35-55% in Kroot to 10-30% in Kstem and Kleaf. In response to treatments, AQP-mediated inhibition of Kroot rather than changes in xylem acclimation controlled the fluctuations in Kroot. The reduction in stomatal conductance and its sensitivity to vapor pressure deficit were direct responses to decreased whole-plant conductance triggered by lower Kroot and larger resistance belowground. Our results provide new mechanistic and functional insights on plant hydraulics that are essential to quantifying the influences of future stress on ecosystem function.
水通道蛋白（AQP）活性对植物水分运动的影响尚不清楚，特别是在植物处于不利条件下时。我们采用多层次的方法，在一系列植物尺度上：（i）描述干旱、水淹和水淹加盐条件下控制水分运输的阻力特征；（ii）量化 AQP 活性和木质部结构对根（Kroot）、茎（Kstem）和叶（Kleaf）导度的各自影响；（iii）评估 AQP 调节的运输能力对气体交换的影响。我们发现，干旱、水淹和水淹加盐降低了湿地松和池杉的 Kroot 和根 AQP 活性，而耐水淹的池杉在水淹条件下 Kroot 并未下降。AQP 对运输效率的控制程度因器官和物种而异，在 Kroot 中为 35-55%，在 Kstem 和 Kleaf 中为 10-30%。对处理的响应，AQP 介导的 Kroot 抑制而不是木质部适应的变化控制了 Kroot 的波动。气孔导度的降低及其对水汽压亏缺的敏感性是对 Kroot 降低和地下阻力增大导致的全株导度降低的直接响应。我们的研究结果为植物水力学提供了新的机制和功能见解，这对于量化未来压力对生态系统功能的影响至关重要。
