Responses of plant stomata to elevated CO_2 and temperature: observations from 10 plant species grown in temperature and CO_2 gradients
植物气孔对大气CO_2浓度和温度升高的反应——基于在CO_2浓度和温度梯度中生长的10种植物的观测

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 temperature. The materials used in our study were obtained from seven herbaceous species commonly found in oldfields of the North American Midwest, including legume, non-legume C 3 and C 4 plants, as well as three deciduous tree species from eastern North America. The results showed that SD was more sensitive to CO 2] changes than SI for all species studied. SD showed either positive, negative or no correlation with CO 2], whereas the SI showed either a positive or no correlation. In the temperature gradient however, SD responded with less sensitivity than SI. SI showed either positive, negative or no correlation with temperature, whereas the SD showed positive or no correlation. Additionally, correlations between ECD and temperature and between APL and temperature differed. Thus, in addition to CO 2], air temperature also affects plant SD, SI, ECD and APL. We suggest that, when reconstructing historical atmospheric CO 2] via analysis of stomatal characteristics, not only must the correlation between CO 2] and stomatal parameters be examined, but the effect of temperature on the correlation should be considered as well.