Drought, variance and physiology: Leaf-level emissions of VOCs from citrus

Plant volatile organic compound (VOC) emissions impact atmospheric composition on local and global scales. Environmental conditions including temperature, ozone, and soil moisture impact those emissions. However, our understanding of these biogenic VOC emissions under different environmental conditions - and thus our ability to model them - is limited. Here, we use concurrent plant physiology and emissions measurements to investigate plant VOC emissions and their response to environmental parameters.

We optimized a method to use a portable photosynthesis system with both online and offline emission analysis. Online analysis using a chemical ionization mass spectrometer enables real-time analysis of oxygenated VOCs such as formic acid. Offline analysis with sorbent tubes coupled to thermal desorption gas chromatography mass spectrometry allows us to measure an array of VOCs including aldehydes and multiple isomers of monoterpenes (C₁₀H₁₆).

We explore the relationship between photosynthesis and other physiological parameters with monoterpene emissions across temperature and light gradients for citrus plants. VOC emissions and physiology show both intraplant (i.e. leafs on the same plant) and interplant (i.e. leafs on different plants) variance. Furthermore, we aim to use drought stress experiments to explore the relationships between plant physiology, VOC emissions and variance.