On-site Visualization of Spatial Distribution of Photosynthesis Using Red, Green, and Blue (RGB) Images of Crop Canopy

Abstract

　Photosynthesis plays a central role in crop productivity. However, measuring canopy-scale photosynthetic rates typically requires expensive chamber systems that limit practical agricultural applications. Here, we developed a low-cost system that visualizes the spatial photosynthetic distribution in crop canopies by combining Red, Green, Blue (RGB) imagery with a biochemical photosynthesis model. RGB values showed strong correlation with photosynthetic photon flux density (PPFD) at both leaf and canopy scales. Our canopy photosynthetic index (A_RGB), which was calculated based on the estimated light intensity from the images, showed strong agreement with the chamber-based measurements. This approach eliminates the need for direct measurement of canopy photosynthetic rates, allowing rapid and easy adaptation to newly introduced crop species. Intuitive visualization of the spatial distribution of photosynthesis has considerable potential as a decision-support tool for cultivation management. This approach offers a practical middle ground for high-precision research tools and field-level monitoring.