Anatomical and hydraulic responses to desiccation in emergent conifer seedlings
Anatomical and hydraulic responses to desiccation in emergent conifer seedlings
复制标题
挺水针叶树幼苗对干燥的解剖学和水力反应
DOI：
10.1002/ajb2.1517
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发表时间：
2020
影响因子：
3
通讯作者：
Johnson, Daniel M.
中科院分区：
文献类型：
--
作者：
Miller, Megan L.;Roddy, Adam B.;Brodersen, Craig R.;McElrone, Andrew J.;Johnson, Daniel M.
幼苗生命阶段对于干扰后的重新造林和气候变化下的物种迁徙至关重要，但对其基本水力功能或对干旱的脆弱性知之甚少。在这里，我们试图描述干燥的反应，包括水力脆弱性，木质部解剖特征，以及对其他有助于水力功能的干组织的影响。方法在干燥过程中，使用x射线计算机显微断层扫描对西部落叶松、门泽松和黄皮松(均为6周龄的≤)进行成像，以同时测量水力传导度(Ks)和水势(Ψ)来评估幼苗的生物力学响应，以评估对木质部血栓形成和其他组织损害的脆弱性。结果在所有物种的非应激样本中，髓和皮质细胞看起来呈圆形和水化良好，但它们开始空洞和变形，Ψ降低，导致细胞撕裂和最终崩溃。尽管这种结构破坏严重，但维管形成层即使在最严重的干旱下也保持良好的水分。不同树种对木质部栓塞物的易感性存在显著差异，木质部栓塞物的易感性为78%。Ψ为2.1兆帕，而−仅为47.7%和62.1%。思考拉和P。结论与其他两种树种相比，西方落叶松苗木更容易发生继发性木质部栓塞，但在严重胁迫下，3种树种均能维持维管形成层的水合作用，缓解胁迫后木质部的再生可促进水力恢复。
PremiseThe young seedling life stage is critical for reforestation after disturbance and for species migration under climate change, yet little is known regarding their basic hydraulic function or vulnerability to drought. Here, we sought to characterize responses to desiccation including hydraulic vulnerability, xylem anatomical traits, and impacts on other stem tissues that contribute to hydraulic functioning.MethodsLarix occidentalis,Pseudotsuga menziesii, andPinus ponderosa(all ≤6 weeks old) were imaged using x‐ray computed microtomography during desiccation to assess seedling biomechanical responses with concurrently measured hydraulic conductivity (ks) and water potential (Ψ) to assess vulnerability to xylem embolism formation and other tissue damage.ResultsIn non‐stressed samples for all species, pith and cortical cells appeared circular and well hydrated, but they started to empty and deform with decreasingΨwhich resulted in cell tearing and eventual collapse. Despite the severity of this structural damage, the vascular cambium remained well hydrated even under the most severe drought. There were significant differences among species in vulnerability to xylem embolism formation, with 78% xylem embolism inL. occidentalisbyΨof −2.1 MPa, but only 47.7% and 62.1% inP. ponderosaandP. menziesiiat −4.27 and −6.73 MPa, respectively.ConclusionsLarix occidentalisseedlings appeared to be more susceptible to secondary xylem embolism compared to the other two species, but all three maintained hydration of the vascular cambium under severe stress, which could facilitate hydraulic recovery by regrowth of xylem when stress is relieved.