School of Natural Sciences, University of Tasmania, Private Bag 55, Hobart, TAS, 7001, Australia.
School of the Environment, Yale University, New Haven, CT, 06520, USA.
New Phytol. 2024 Nov;244(4):1288-1302. doi: 10.1111/nph.20115. Epub 2024 Sep 12.
Resolving the position of roots in the whole-plant hierarchy of drought-induced xylem embolism resistance is fundamental for predicting when species become isolated from soil water resources. Published research generally suggests that roots are the most vulnerable organ of the plant vascular system, although estimates vary significantly. However, our knowledge of root embolism excludes the fine roots (< 2 mm diameter) that form the bulk of total absorptive surface area of the root network for water and nutrient uptake. We measured fine root and stem xylem vulnerability in 10 vascular plant species from the major land plant clades (five angiosperms, three conifers, a fern and lycophyte), using standardised in situ methods (Optical Methods and MicroCT). Mean fine root embolism resistance across the network matched or exceeded stems in all study species. In six of these species (one fern, one lycophyte, three conifers and one angiosperm), fine roots were significantly more embolism resistant than stems. No clear relationship was found between root xylem conduit diameter and vulnerability. These results provide insight into the resistance of the plant hydraulic pathway at the site of water and nutrient uptake, and challenge the long-standing assumption that fine roots are more vulnerable than stems.
解决干旱诱导木质部栓塞抗性中根系在整个植物层次结构中的位置对于预测物种何时与土壤水资源隔离至关重要。已发表的研究普遍表明，尽管估计值差异很大，但根系是植物维管系统中最脆弱的器官。然而，我们对根栓塞的了解排除了形成根系网络总吸收表面积大部分的细根（<2mm 直径），这些细根用于吸收水和养分。我们使用标准化的原位方法（光学方法和 MicroCT）测量了来自主要陆地植物类群（五个被子植物、三个针叶树、一个蕨类植物和一个石松类植物）的 10 种维管植物的细根和茎木质部脆弱性。在所有研究物种中，网络中平均细根栓塞抗性与茎相当或超过茎。在这 6 个物种（一个蕨类植物、一个石松类植物、三个针叶树和一个被子植物）中，细根比茎具有显著更高的栓塞抗性。在木质部导管直径和脆弱性之间没有发现明显的关系。这些结果提供了对植物水力途径在水和养分吸收部位的抗性的深入了解，并挑战了细根比茎更脆弱的长期假设。
