Long-term Responses of Stomatal Characteristics to [CO2] in Great Basin Plants

One of the environmental changes that has been a concern around the world is an increase in atmospheric [CO2]. Because changes in stomatal density and size with changes in atmospheric [CO2] have been observed in some studies, this senior thesis analyzed if any trends (either increasing or decreasing) occurred in Great Basin plants over the past century. Plant epidermal impressions were taken by using clear nail polish and cellophane tape. After a patch of nail polish was dried, the patch was peeled off by using cellophane tape. The tape with the patch was mounted on a slide. However, no significant change through time was observed for either stomatal density or stomatal size except for two species. Stomatal size for C3 annual forb Chenopodium atrovirens significantly decreased through time, which is expected if increasing atmospheric [CO2] affects leaf stomata as predicted. Interestingly, stomatal size of the C4 perennial grass Muhlenbergia asperifolia significantly increased through time, which differed from the expectation of no change through time for C4 species. Possible reasons for not obtaining the expected decreasing trend in most species could be: (1) the change in atmospheric [CO2] was not large enough to cause a significant change in stomatal morphological characteristics, (2) Great Basin plants might adapt to increasing atmospheric [CO2] by changing physiological characteristics, not stomatal morphological characteristics, or (3) atmospheric [CO2] might not be an evolutionary factor that is strong enough to change stomatal morphological characteristics of Great Basin plants