Coordinated decline of leaf hydraulic and stomatal conductances under drought is not linked to leaf xylem embolism for different grapevine cultivars
Coordinated decline of leaf hydraulic and stomatal conductances under drought is not linked to leaf xylem embolism for different grapevine cultivars
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DOI：
10.1093/jxb/eraa392
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发表时间：
2020-12-31
影响因子：
6.9
通讯作者：
McElrone, Andrew J.
中科院分区：
文献类型：
--
作者：
Albuquerque, Caetano;Scoffoni, Christine;McElrone, Andrew J.
干旱降低了叶片的水输送能力并限制了气体交换，这涉及木质部和木质部外途径中叶片水力传导（K叶）的降低。一些文献表明，葡萄藤对干旱引起的木质部栓塞非常敏感。我们结合了 Kleaf 和气体交换测量、完整叶子的微型计算机断层扫描以及外部木质部路径的空间显式建模，以评估静脉栓塞和 K 叶在两种不同葡萄品种对干旱的响应中的作用。赤霞珠和霞多丽表现出类似的 K 叶和 g(s) 对脱水的脆弱性，在叶木质部栓塞之前显着降低。 Psi（叶）约-0.7 MPa和-1.2 MPa时，两个品种的K叶和g（s）下降了80％，而叶木质部栓塞在中脉中Psi（叶）= -1.25 MPa左右开始，即使在两个品种严重脱水的情况下，小脉中也几乎没有检测到栓塞。模拟结果表明，与叶脉束鞘中的凯氏样带相关的膜通透性降低可以解释两个品种 K 叶的下降。我们的结论是，在中度水分胁迫期间，外部木质部途径的变化，而不是木质部栓塞，是导致 K 叶和 g(s) 减少的原因。了解这一机制有助于确保干旱条件下充分的碳捕获和作物生长。
Drought decreases water transport capacity of leaves and limits gas exchange, which involves reduced leaf leaf-hydraulic conductance (K-leaf) in both the xylem and outside-xylem pathways. Some literature suggests that grapevines are hyper-susceptible to drought-induced xylem embolism. We combined Kleaf and gas exchange measurements, micro-computed tomography of intact leaves, and spatially explicit modeling of the outside-xylem pathways to evaluate the role of vein embolism and K-leaf in the responses of two different grapevine cultivars to drought. Cabernet Sauvignon and Chardonnay exhibited similar vulnerabilities of K-leaf and g(s) to dehydration, decreasing substantially prior to leaf xylem embolism. K-leaf and g(s) decreased by 80% for both cultivars by Psi(leaf) approximately -0.7 MPa and -1.2 MPa, respectively, while leaf xylem embolism initiated around Psi(leaf) = -1.25 MPa in the midribs and little to no embolism was detected in minor veins even under severe dehydration for both cultivars. Modeling results indicated that reduced membrane permeability associated with a Casparian-like band in the leaf vein bundle sheath would-explain declines in K-leaf of both cultivars. We conclude that during moderate water stress, changes in the outside-xylem pathways, rather than xylem embolism, are responsible for reduced K-leaf and g(s). Understanding this mechanism could help to ensure adequate carbon capture and crop performance under drought.