EAGER: Real-time measurement of sap-flow dynamics in sunflower via nuclear magnetic resonance

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Water is a key component to our planet, particularly to sustain food production and support human existence. To use water judiciously at macro scales e.g., basins or watersheds, a thorough understanding of factors affecting water requirement at smaller scales e.g., individual plants, is required. At the plant scale, the main driver determining water need is transpiration from the leaves. The rate of water loss through leaves is directly linked to sap flow, defined as the rate at which water moves through the stem. The goal of this project is to develop a new technology using principles from physics, based on nuclear magnetic resonance (NMR), to accurately determine sap flow and how it changes in real-time in a plant stem under different environmental conditions. Unlike currently available equipment, the NMR tool is non-invasive and portable, which allows making in-situ measurements easy and handy. Results from the NMR tool will have broad impacts that are of societal relevance by filling a significant knowledge gap about water and nutrient transport in plants. Project personnel will be involved in on-campus activities and events to engage K-12 students and increase their knowledge regarding water management. Project PIs will work with underrepresented groups in science for the Advancement of Women in Science and Engineering (KAWSE) i.e., Girls Researching Our World (GROW) summer workshops focusing on the water use and new NMR technology. The NMR tool has the potential for commercialization and application to other food crops and plants to advance agricultural and ecosystem productivity. The sole phenomenon transporting water and nutrients from soil to leaves through roots and stem vascular tissues in plants is the highly-dynamic sap flow. Quantifying this extremely complex physiological process varying temporally and spatially has been a major challenge in crop science, due to the lack of a robust, non-invasive and portable system. Therefore, this project aims to (1) design and prototype a handy tool to accurately measure temporal variations of sap-flow dynamics in sunflower, and (2) test and validate nuclear magnetic resonance (NMR) as a useful and practical tool for characterizing sap flow in crop plants. A portable NMR tool will be designed using a combination of 3D finite-element simulation package and a non-dominated sorting genetic algorithm-II to optimize the magnets' arrays and coils. The optimally-designed NMR tool will be prototyped in the lab, and its magnetic field homogeneity and intensity will be experimentally validated. Furthermore, a narrow tube and two flow rates i.e., 1 and 100 (mg/s) will be used to fine-tune the NMR tool under steady-steady conditions. Sunflower plants will be maintained in state-of-the-art, walk-in growth chambers at 2, 3 and 4 kPa vapor pressure deficit levels. Plant water loss will be measured at high temporal frequency using a load cell and the mass-balance method. NMR velocimetry will be performed thrice daily at different growth stages until flowering to capture velocity distribution at short time intervals. Sap flow estimated via NMR will be compared with that determined by the mass-balance method.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.