Physiology and Isoprene Emissions of Drought-Stressed and Ozone Exposed Plants in a Laboratory Chamber

The effect of isoprene, the most dominantly emitted volatile organic compound (VOC) by vegetation, can play a pivotal role in today's tropospheric air chemistry. In our changing climate, isoprene is expected to significantly contribute to the feedback between climate change and biogeochemical processes; therefore, it is worthwhile to study the effect of a changing climate on the physiology and isoprene emissions of trees. In this experiment, several species of isoprene-emitting oak trees will be subjected to different levels of soil moisture and ozone exposure to observe and analyze their changes in physiology and emissions. This will be achieved by the use of an established laboratory-based Teflon foil chamber that is designed for trace gas exchange analysis of live plants. Compressed, particle-free, charcoal-filtered, and re-humidified air with 400+ ppm CO₂ is used in the chamber; ozone is introduced with a UV-ozone generator using zero air. The setup allows for the manipulation of variables such as light levels (from daylight LED bulbs) and gas composition similar to a growth chamber; measurements of temperature, humidity, and gas concentrations of the chamber are constantly recorded with a data logger. The use of potted oak trees allows for the simulation of drought stress through regulation of soil moisture. This laboratory experiment will explore the effects of limited soil moisture in combination with elevated ozone exposure, two parameters typically occurring during dry spells and drought periods in Texas. Whole plant physiology and isoprene emissions of the trees after acclimation to the chamber environment are followed in a reproducible manner. Using the data from this chamber, a relationship between environmental stresses and isoprene emissions can be determined for the trees used in the experiment, and our results can therefore inform expected changes in isoprene emissions.