Relationship between stomatal density and the changes of atmospheric CO2 concentrations

The relationship between the stomatal density of five woody plants endemic to China, i. e.Eucommia ulmoides, Quercus liaotungensis, Q. glandulifera var.brevipetiolata, Cyclocarya paliurus andFicus heteromorpha, and the atmospheric CO₂ concentrations was studied by observations on leaves of the herbarium-stored specimms(1920s–1990s). The results showed that the stomatal density inEucommia ulmoides, Quercus liaotungensis andQ. glandulifera var.brevipetiolata decreased significantly in response to the elevated atmospheric CO₂ concentrations, while inCyclocarya paliurus it decreased slightly and inFicus heteromorpha there were no responses.