Photosynthesis and leaf-level monoterpene emissions during seasonal senescence

Plant volatile organic compound (VOC) emissions impact atmospheric composition both locally and globally. Environmental conditions including temperature, ozone, and soil moisture, impact those VOC emissions. However, our understanding of how biogenic VOC emissions change during the seasonal senescence of leaves is limited, thus limiting our ability to model atmospheric VOCs. Here, we use concurrent leaf photosynthesis and emissions measurements to investigate the response of VOC emissions to the first seasonal snow, and subsequent seasonal senescence.

We use a portable photosynthesis system coupled to sorbent tubes to simultaneously measure leaf photosynthesis and collect leaf-level VOC emissions. We analyze the emission samples using thermal desorption gas chromatograph mass spectrometry and focus our analysis on several different isomers of monoterpenes (C₁₀H₁₆). We explore the relationship between photosynthesis and stomatal conductance with monoterpene emissions for one cultivar of tulip tree (Liriodendron tulipifera `JFS-Oz'). This cultivar is notable as a monoterpene-emitting cultivar of this species.

Our study investigates intra-plant variability (several leaves of one plant) and environmental response (e.g., varying temperatures) both before and after the first seasonal snow. We provide a monoterpene emission profile and investigate its changes following a snow event, including an overall decrease in monoterpene emissions. We further describe emissions as leaves senesce, and we provide evidence for the humidity dependence of monoterpene emissions.