Terahertz Laser Leaf Scanner to Reduce Urban Ecosystem Water Expenditure

Project Summary

Plant water use in lawns and trees accounts for a major portion of water use in Los Angeles. Further, natural and agricultural ecosystems across the U.S. are vulnerable to increasing droughts that have caused mass tree mortalities. This project's cross-disciplinary research aims to catalyze discovery, technology development and application to strongly reduce irrigation water expenditure and to anticipate tree mortality from natural drought.

Researchers are optimizing terahertz laser detection of leaf water status for multiple species in order to develop a new instrument and sensor that rapidly determines the degree of drought that plants are experiencing and the water required for their survival and growth. The project aims to design a device that can be hand-held or deployed on a drone for remote sensing of leaf water content within leaves for lawns or urban trees, or interfaced with irrigation systems, reducing irrigation water in lawns for residential and commercial landscapes, street trees, arboreta, parks and campuses. This technology can enable major reductions of water expenditure, which could lead to major savings in water.

Research Team

Lawren Sack
Ecology & Evolutionary Biology, Life Sciences

Mona Jarrahi
Electrical Engineering, Samueli School of Engineering 

Benjamin Williams
Electrical Engineering, Samueli School of Engineering

Progress and Results

The team has quantified the relationship of Terahertz absorption to leaf water potential - the most informative index of leaf water status or drought stress - for urban los Angeles trees sycamore (Platanus racemosa) and ivy (Hedera canariensis) and are currently measuring Arabidopsis thaliana, which is the most important plant genetic model. This work has shown that THz absorption has very strong power to estimate even subtle leaf water stress remotely, and will be of great use for improved irrigation systems and predicting drought damage to crops and urban trees. This project’s refinement of THz measurements for leaves and statistical analysis will have applications worldwide to a wide range of species. Researchers have also begun refining the measurements to estimate leaf thickness, which will even further improve the estimation of leaf water status.