Carbon stable isotope composition of berry must at harvest (δ13C) is an integrated assessment of plant water status during grape (Vitis vinifera L.) berry ripening. Measurement of δ13C of grape juice is proposed as an alternative to traditional measurements of water status to capture the spatial variability of physiological response at the vineyard scale, i.e., zoning. We performed samplings at four different locations in California, United States, with three different cultivars of table and wine grapes (Cabernet Sauvignon, Merlot, Crimson-Seedless). Leaf physiology (photosynthesis, AN, stomatal conductance, gs) and stem water potentials (Ψstem) were routinely measured. The δ13C was measured at harvest and strong relationships were found between Ψstem (R2 = 0.71), stomatal conductance (R2 = 0.71), net carbon assimilation (R2 = 0.59) and WUEi (R2 = 0.53). The role of leaf nitrogen on the signal was assessed by evaluating relationships between leaf nitrogen and WUEi (R2 = 0.54), Ci/Ca (R2 = 0.51), δ13C (R2 = 0.44), and Ψstem (R2 = 0.37). Although nitrogen can be among the environmental factors able to affect the δ13C signal, this difference is only observable when variability in N is very large, by pooling different vineyards/varieties, but not at the within-vineyard scale. The utility of δ13C was further tested and measured on grape berries sampled on an equidistant grid in a 3.5 ha vineyard where Ψstem was also measured throughout the field season and used to delineate management zones. Physiological measurements and grape composition were correlated to soil electrical resistivity and satellite-derived vegetation index. The two management zones obtained by δ13C or Ψstem were spatially similar at 67% and allowed to separate the harvest in two pools having statistically different grape composition (soluble solids, organic acids, and anthocyanin profiles). Zoning by δ13C performed as well as zoning by Ψstem to separate grape phenolic composition, e.g., for selective harvest. Our results provided evidence that δ13C of grape must is a reliable and repeatable assessor of plant water status and gas exchange in vineyard systems that are crucial for zoning vineyards, even when irrigated, and for ground-truthing sensor maps in precision viticulture.

中文翻译：

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葡萄汁的碳同位素鉴别 (δ13 C) 是精确葡萄栽培中传感器图的分区和生理学真实性的可靠工具

收获时浆果的碳稳定同位素组成 (δ13C) 是对葡萄 (Vitis vinifera L.) 浆果成熟期间植物水分状况的综合评估。建议测量葡萄汁的 δ13C 作为传统水分状态测量的替代方法，以捕捉葡萄园尺度（即分区）生理反应的空间变异性。我们在美国加利福尼亚州的四个不同地点对三种不同的食用葡萄和酿酒葡萄品种（赤霞珠、梅洛、深红无籽）进行了采样。叶生理（光合作用，AN，气孔导度，gs）和茎水势（Ψstem）被常规测量。在收获时测量 δ13C，发现 Ψstem (R2 = 0.71)、气孔导度 (R2 = 0.71)、净碳同化 (R2 = 0. 59) 和 WUEi (R2 = 0.53)。通过评估叶氮与 WUEi (R2 = 0.54)、Ci/Ca (R2 = 0.51)、δ13C (R2 = 0.44) 和 Ψstem (R2 = 0.37) 之间的关系来评估叶氮对信号的作用。尽管氮可能是能够影响 δ13C 信号的环境因素之一，但这种差异仅在 N 的变异性非常大时才能观察到，通过汇集不同的葡萄园/品种，而不是在葡萄园内规模。δ13​​C 的效用在 3.5 公顷葡萄园的等距网格上采样的葡萄浆果上进行了进一步测试和测量，其中 Ψstem 也在整个田间季节进行了测量，并用于划定管理区域。生理测量和葡萄成分与土壤电阻率和卫星衍生的植被指数相关。通过 δ13C 或 Ψstem 获得的两个管理区在空间上相似，为 67%，并允许将收获物分为两个具有统计学差异的葡萄成分（可溶性固体、有机酸和花青素谱）。通过 δ13C 进行分区以及通过 Ψstem 进行分区以分离葡萄酚类成分，例如，用于选择性收获。我们的结果提供证据表明，葡萄的 δ13C 必须是葡萄园系统中植物水分状况和气体交换的可靠且可重复的评估器，这对于葡萄园分区（即使在灌溉时）以及精确葡萄栽培中的地面真实传感器图至关重要。通过 δ13C 进行分区以及通过 Ψstem 进行分区以分离葡萄酚类成分，例如，用于选择性收获。我们的结果提供证据表明，葡萄的 δ13C 必须是葡萄园系统中植物水分状况和气体交换的可靠且可重复的评估器，这对于葡萄园分区（即使在灌溉时）以及精确葡萄栽培中的地面真实传感器图至关重要。通过 δ13C 进行分区以及通过 Ψstem 进行分区以分离葡萄酚类成分，例如，用于选择性收获。我们的结果提供证据表明，葡萄的 δ13C 必须是葡萄园系统中植物水分状况和气体交换的可靠且可重复的评估器，这对于葡萄园分区（即使在灌溉时）以及精确葡萄栽培中的地面真实传感器图至关重要。