The Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.
The Arnold Arboretum of Harvard University, Boston, MA, 02131, USA.
New Phytol. 2021 Dec;232(6):2238-2253. doi: 10.1111/nph.17629. Epub 2021 Aug 8.
While a considerable amount of data exists on the link between xylem construction and hydraulic function, few studies have focused on resistance to drought-induced embolism of primary vasculature in herbaceous plants. Ferns rely entirely on primary xylem and display a remarkable diversity of vascular construction in their rhizomes, making them an ideal group in which to examine hydraulic structure-function relationships. New optical methods allowed us to measure vulnerability to embolism in rhizomes, which are notoriously difficult to work with. We investigated five fern species based on their diverse xylem traits at the cellular, histological, and architectural levels. To link below- and above-ground hydraulics, we then measured leaf-stem vulnerability segmentation. Overall, rhizome vulnerability to embolism was correlated most strongly with cellular but not histological or architectural traits. Interestingly, at P , species with increased architectural dissection were actually more vulnerable to embolism, suggesting different hydraulic dynamics at low compared to high percent embolism. Importantly, leaves fully embolize before stems reach P , suggesting strong vulnerability segmentation. This is the first study to explore the functional implications of primary vascular construction in fern rhizomes and leaf-stem vulnerability segmentation. Strong segmentation suggests that leaves protect perennial rhizomes against severe drought stress and hydraulically induced mortality.
虽然有相当多的数据表明木质部结构与水力功能之间存在联系，但很少有研究关注草本植物初生维管束对干旱引起的栓塞的抵抗力。蕨类植物完全依赖初生木质部，在其根茎中表现出显著的血管结构多样性，使它们成为研究水力结构-功能关系的理想群体。新的光学方法使我们能够测量根茎对栓塞的脆弱性，而根茎是众所周知的难以处理的。我们根据细胞、组织学和结构水平上的不同木质部特征，研究了五种蕨类植物。为了将地下和地上的水力联系起来，我们测量了叶-茎脆弱性分段。总的来说，根茎对栓塞的脆弱性与细胞特征而非组织学或结构特征密切相关。有趣的是，在 P 点，具有增加的结构解剖的物种实际上更容易受到栓塞的影响，这表明与高栓塞百分比相比，低栓塞百分比的水力动态不同。重要的是，叶片在茎达到 P 点之前完全栓塞，这表明脆弱性分段很强。这是第一项探索蕨类植物根茎初生维管束和叶-茎脆弱性分段的功能意义的研究。强烈的分段表明，叶片可以保护多年生根茎免受严重干旱胁迫和水力诱导的死亡。
