The supply of water to a plant canopy is dependent on the xylem pathway connecting roots to leaves. In some plants, sectored xylem pathways can restrict resource distribution, resulting in variable quality of organs in the shoots, yet little is known about the effects of sectoring in crop cultivars. In this study, we combined sap flow measurements and infusion of xylem-specific dyes to document functional conductive area and flow pathways from roots to shoots of 20-year-old Thompson Seedless and 8-year-old Chardonnay grapevines. Sap flow measurements and dye infusion demonstrated that water flowed predominantly in discrete xylem (visually identifiable from the trunk surface) sectors along the trunk axis, each supplying limited portions of the canopy. Functional conductive area in the trunk was proportional to that in the shoots even though sector size varied considerably between vines. Leaf area removal experiments further demonstrated sectoring in grapevines; sap flow decreased by >90 % in trunk sectors connected to excised shoots while it remained constant in trunk sectors supplying intact portions of the canopy. Despite the functional sectoring in grapevines, a high degree of interconnectivity of trunk xylem in the tangential direction was confirmed with synchrotron-based micro-computed tomography (microCT) and dye crossover infusion studies. Fruit attached to dyed canes was also similarly sectored; no clusters exhibited dye on non-dyed canes, while 97 % of clusters attached to dyed canes exhibited dye infusion. The dye travelled down the cluster rachis and appeared to accumulate at the pedicel/berry junction, but only on dyed canes. These findings suggest that xylem in grapevine trunks is integrated anatomically, but functions in a sectored manner due to high axial hydraulic conductivity. The functional sectoring of grapevine xylem documented here has important implications for management practices in vineyards and for fruit cluster uniformity within single grapevine.

中文翻译：

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葡萄藤的功能性液压分区，如液流、染料注入、叶片去除和微型计算机断层扫描所证明

植物冠层的水供应取决于连接根与叶的木质部通路。在一些植物中，扇形木质部路径会限制资源分布，导致枝条中器官的质量参差不齐，但对作物品种中扇形的影响知之甚少。在这项研究中，我们将液流测量和木质部特异性染料的注入相结合，以记录 20 岁的 Thompson 无核葡萄藤和 8 年的霞多丽葡萄藤从根部到枝条的功能传导区域和流动路径。液流测量和染料注入表明，水主要在沿树干轴线的离散木质部（从树干表面视觉识别）部分流动，每个部分都供应有限的树冠部分。树干中的功能导电面积与枝条中的导电面积成正比，尽管葡萄藤之间的扇区大小差异很大。叶面积去除实验进一步证明了葡萄藤的扇形；与切除的枝条相连的树干部分的液流减少了＞90%，而提供完整树冠部分的树干部分的液流保持不变。尽管葡萄藤中存在功能分区，但基于同步加速器的微型计算机断层扫描 (microCT) 和染料交叉注入研究证实了树干木质部在切向方向上的高度互连。附着在染色手杖上的水果也被类似地分割；未染色的手杖上没有簇显示染料，而附着在染色手杖上的簇中有 97% 显示染料注入。染料沿着簇轴向下移动，并似乎在花梗/浆果连接处积聚，但仅在染色的手杖上。这些发现表明，葡萄树干中的木质部在解剖学上是整合的，但由于轴向水力传导率高，以扇形方式发挥作用。这里记录的葡萄木质部的功能分区对葡萄园的管理实践和单个葡萄树内的果实簇均匀性具有重要意义。