Increases in the frequency and severity of droughts across many regions worldwide necessitates an improved capacity to determine the water status of plants at organ, whole plant, canopy and regional scales. Non-invasive 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, i.e., water mass per leaf area (WMA), relative water content (RWC) and leaf water potential (Ψleaf) require the excision of tissues and lab 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 Ψleaf. We estimated the water status of dehydrating leaves for three species of diverse phylogeny, habitat type and responses to drought: Arabidopsis thaliana(Col-O), Hedera canariensis, and Platanus racemosa.
Results/Conclusions
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 Ψleaf 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.