Photosynthesis is a complex process that consumes carbon dioxide and water to produce oxygen and glucose. Studies to investigate leaf-level photosynthetic activity have been conducted using systems that control certain parameters such as light intensity or partial pressure of CO2. For instance, the LI-COR LI‑6800 Portable Photosynthesis System enables the user to control and measure light, temperature, CO2 and water vapor concentrations. Measurement of O2 fluxes concurrent with CO2 exchange and other parameters is a technical challenge since a very high level of precision on a large O2 background is required. Only few analytical methods including mass spectrometry, fuel cell, ultraviolet and paramagnetic cells can achieve the required high-precision O2 analysis.
Here we present new developments of a high-precision gas analyzer that utilizes the technique of Cavity Ring-Down Spectroscopy to measure oxygen concentrations. Its compact and rugged design combined with high-precision and long-term stability allow the user to deploy the instrument in the field for continuous monitoring of atmospheric oxygen level. Measurements have a 1-σ 5-minute averaging precision of 1-2 ppm for O2 over a dynamic range of 0-25%. We present collaborative work with LI‑COR where we coupled the Picarro G2207-i O2 analyzer with the LI-6800 Portable Photosynthesis System to enable O2 analysis for laboratory studies of photosynthesis. To validate the setup, we conducted light and CO2 response experiments.