76 Stomatal Density as a Proxy of Changing Atmospheric Conditions in Pinus longaeva: exploring responses in stomatal conductance

Faculty Mentor: Mitchell Power (Geography, University of Utah)

Prior to the Industrial Revolution natural variations in the Earth’s atmosphere created an average amount of carbon dioxide (CO2) of ~280 ppm (parts per million). Currently, according to the National Oceanic and Atmospheric Administration, the current level of atmospheric CO2 is at 426.90 ppm. The drastic jump is linked to anthropogenic activity and the rate at which CO2 is accumulating in the atmosphere continues to rise annually. This new input of CO2 over recent decades is changing the composition of atmospheric gas concentrations, leaving the future of CO2 uptake through land-based ecosystems services highly uncertain. Key aspects of vegetation dynamics are photosynthesis, evapotranspiration, and water use efficiency. Stomata, the small epidermal cells that open and close that allow a plant to take in and release gases, can be used to interpret these key processes in the past. Recent studies report that the plasticity of stomata to CO2 therefore appeared to be lost in plants exposed to elevated CO2 over several years whereas, leaves grown in ambient CO2 were still responsive to elevated atmospheric carbon and there were large increases in photosynthetic rate and leaf-level water use efficiency. The purpose of this project is to investigate stomatal changes over a range of atmospheric conditions specifically in Pinus longaeva, or bristlecone pine to better understand how stomatal density performs as a proxy for stomatal conductance. If a stable reduction in stomatal conductance over long-term exposure to elevated CO2 is observed, these findings will have major implications for modeling plant responses to climate change.