Design and Characterization of a Compact and Lightweight Dual-Wavelength Chlorophyll Fluorescence Light Detection and Ranging Sensor (ChloroFLiDAR) for Remote Plant Stress Assessment

Chlorophyll Fluorescence (ChlF) provides valuable biophysical insights into the photosynthetic status of plants, serves as an indicator of plant stress and can be measured using simple, non-invasive methods. Therefore, it can be a powerful tool for remote sensing and large-scale vegetation monitoring. In this study, we introduce a novel, lightweight, and portable dual-wavelength Chlorophyll Fluorescence Light Detection and Ranging sensor (ChloroFLiDAR) designed for photosynthesis research and remote plant stress assessment. The sensor utilizes modulated laser light to induce ChlF and employs an I/Q lock-in amplification method to isolate the signal from background noise, thereby enhancing measurement sensitivity. This approach enables accurate ChlF measurements under varying ambient light conditions, along with measurement of the distance to the leaves. Our results demonstrate that the sensor can detect ChlF at a distance of 10 m with an integration time of 65.5 μs. Additionally, experiments on European beech (Fagus sylvatica) seedlings subjected to water stress and high light intensity demonstrated the sensor's ability to detect changes in ChlF indices due to plant stress.