Abstract:Many studies have reported that increases in atmospheric CO 2 concentration ([CO 2]) lead to decreases in plant stomatal density (SD) and stomatal index (SI). These correlations have become key proxies for the estimation of paleoatmospheric [CO 2]. However, [CO 2] is not the only environmental factor affecting SD and SI. In this study, we conducted an experiment with controlled temperature and [CO 2] gradients to examine the correlation between stomatal characters and both elevated [CO 2] and temperat...