Simultaneous leaf-level measurement of trace gas emissions and photosynthesis with a portable photosynthesis system

• Main Authors: M. Riches, D. Lee, D. K. Farmer
• Format: Article
• Language: English
• Published: Copernicus Publications 2020-08-01
• Series: Atmospheric Measurement Techniques
• Online Access: https://amt.copernicus.org/articles/13/4123/2020/amt-13-4123-2020.pdf

<p>Plants emit considerable quantities of volatile organic compounds (VOCs), the identity and amount of which vary with temperature, light, and other environmental factors. Portable photosynthesis systems are a useful method for simultaneously quantifying in situ leaf-level emissions of VOCs and plant physiology. We present a comprehensive characterization of the LI-6800 portable photosynthesis system's ability to be coupled to trace gas detectors and measure leaf-level trace gas emissions, including limits in flow rates, environmental parameters, and VOC backgrounds. Instrument contaminants from the LI-6800 can be substantial but are dominantly complex molecules such as siloxanes that are structurally dissimilar to biogenic VOCs and thus unlikely to interfere with most leaf-level emissions measurements. We validate the method by comparing <span class="inline-formula">CO₂</span> assimilation calculated internally by the portable photosynthesis system to measurements taken with an external <span class="inline-formula">CO₂</span> gas analyzer; these assimilation measurements agree within 1&thinsp;%. We also demonstrate both online and offline measurements of plant trace gas exchange using the LI-6800. Offline measurements by pre-concentration on adsorbent cartridges enable the detection of a broad suite of VOCs, including monoterpenes (e.g., limonene) and aldehydes (e.g., decanal). Online measurements can be more challenging if flow rates require dilution with ultrapure zero air. We use high-resolution time-of-flight chemical ionization mass spectrometry coupled to the LI-6800 to measure the direct plant emission of formic acid.</p>