Changes in Stomatal Conductance in Response to Rising Atmospheric Carbon Dioxide Levels

Ever since the emergence of the first plant species, plants have been altering their physiology in response to changes in external stimuli. One important factor for plants is the continual change in atmospheric carbon dioxide levels throughout Earth’s history. Stomatal conductance is one plant characteristic that has been affected by the atmospheric carbon dioxide levels at short and long-time scales. Stomatal conductance is the diffusivity of water vapor and CO2 across the distance of the stomatal pore. To assess the stomatal conductance of plants over approximately a century, herbarium specimen from the Baylor Herbarium (BAYLU) were selected and scanned under a 3-D laser microscope. was selected to represent the monilophyes, Osmunda regalis Rubus trivialis and Prunus serotina the gymnosperms, and study hypothesized that the angiosperms would exhibit greater plasticity in their stomatal for the angiosperms. This conductance in response to increasing atmospheric carbon dioxide, which meant significant changes would be made in their stomatal physiology and/or density. Upon analysis, it was found that only Rubus trivialis exhibited significant changes in stomatal conductance in response to increasing atmospheric carbon dioxide. Further analysis on vein density, water use efficiency, and plant response to carbon dioxide levels were made based on the findings.