Clonal variation in stomatal characteristics related to biomass production of 12 poplar (Populus) clones in a short rotation coppice culture

Twelve poplar (Populus) clones, belonging to different species and interspecific hybrids, were studied during the third growing season of the second rotation of a high density coppice culture. Stomatal characteristics, as stomatal density and stomatal length, were examined for fully expanded leaves from all clones and at two canopy positions (upper and lower canopy). Above-ground biomass production was assessed by destructive harvesting and varied significantly among clones. Leaves of all clones were amphistomatous except for clones belonging to the Populus trichocarpa parentage. Abaxial stomatal density was higher than adaxial stomatal density for all clones and for both canopy positions. Significant clonal variations in stomatal density and length were observed. Significant differences were also found between the two canopy positions for both stomatal density and length. Upper canopy leaves had higher stomatal density than lower canopy leaves. Variations in stomatal characteristics were related to the parentage of the clones and to the canopy position within each clone. Biomass was positively and significantly correlated with abaxial stomatal density, i.e., clones with high density showed high biomass production. We conclude that stomatal density of different poplar clones affected biomass production.