Increases in the frequency and severity of droughts across many regions worldwide necessitate an improved capacity to determine the water status of plants at organ, whole plant, canopy, and regional scales. Noninvasive methods have most potential for simultaneously improving basic water relations research and ground‐, flight‐, and space‐based sensing of water status, with applications in sustainability, food security, and conservation. The most frequently used methods to measure the most salient proxies of plant water status, that is, water mass per leaf area (WMA), relative water content (RWC), and leaf water potential (Ψ_leaf), require the excision of tissues and laboratory analysis, and have thus been limited to relatively low throughput and small study scales. Applications using electromagnetic radiation in the visible, infrared, and terahertz ranges can resolve the water status of canopies, yet heretofore have typically focused on statistical approaches to estimating RWC for leaves before and after severe dehydration, and few have predicted Ψ_leaf. Terahertz radiation has great promise to estimate leaf water status across the range of leaf dehydration important for the control of gas exchange and leaf survival. We demonstrate a refined method and physical model to predict WMA, RWC, and Ψ_leaf from terahertz transmission across a wide range of levels of dehydration for given leaves of three species, as well as across leaves of given species and across multiple species. These findings highlight the powerful potential and the outstanding challenges in applying in vivo terahertz spectrometry as a remote sensor of water status for a range of applications.

中文翻译：

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使用太赫兹辐射光谱预测叶片水势和相对含水量。


全球许多地区干旱频率和严重程度的增加需要提高确定植物器官、整个植物、冠层和区域尺度水分状况的能力。非侵入性方法最有潜力同时改善基础水关系研究以及基于地面、飞行和空间的水状况感知，并在可持续发展、粮食安全和保护方面得到应用。最常用的方法来测量植物水分状况的最显着指标，即每叶面积的水质量 (WMA)、相对含水量 (RWC) 和叶水势 (Ψ _leaf )，需要切除组织和实验室分析，因此仅限于相对较低的通量和较小的研究规模。使用可见光、红外和太赫兹范围内的电磁辐射的应用可以解决冠层的水分状况，但迄今为止通常集中于统计方法来估计严重脱水前后叶子的 RWC，很少有人预测 Ψ _leaf 。太赫兹辐射有望估计整个叶片脱水范围内的叶片水分状况，这对于控制气体交换和叶片存活至关重要。我们展示了一种改进的方法和物理模型，可以通过太赫兹传输来预测三个物种的给定叶子、跨给定物种的叶子和跨多个物种的叶子的 WMA、RWC 和 Ψ_叶子，这些传输跨越了广泛的脱水水平。这些发现凸显了体内太赫兹光谱测量作为水状态远程传感器在一系列应用中的巨大潜力和突出挑战。