Establishment of a low-cost photosynthesis measurement system based on a single-board microcomputer and CO₂ sensors

Leaf photosynthetic rate serves as a growth indicator in plant science; however, the high cost (exceeding USD 70,000) of traditional measurement system is the main concern when making photosynthesis measurements of interest to a wide range of users. Recently, the availability of inexpensive environmental sensors and single-board microcomputers has increased substantially. In this study, we selected CO₂ sensors based on a comparative analysis of four cost-effective sensors. The economical K30 sensor demonstrated a superior response to CO₂ fluctuations, compared to the other tested low-cost sensors, and exhibited noise-free stability relative to the values recorded by the high-precision system (LI-850). A closed-chamber system was constructed, incorporating the K30 sensor into a self-made chamber controlled by a single-board microcomputer. The materials for the demo device incurred an approximate cost of USD 200, resulting in a low overall expense. Leaf photosynthesis measurements for sugarcane germplasm from the demo device were compared with those from a standard open system (LI-6400), revealing a significant correlation (p < 0.001). The root mean square error (RMSE) and relative RMSE were 1.4 and 7.6% under artificial light conditions (n = 50) and 3.6 and 13.3% under natural field light conditions (n = 45), respectively. The constructed low-cost photosynthesis measurement system, utilizing the K30 CO₂ sensor and a single-board microcomputer, demonstrated high responsiveness and accuracy comparable to commercial standard systems, thereby making it accessible and practical for a broader range of users. Future work will involve selecting an inexpensive humidity sensor and establishing a system for measuring water-use efficiency.