A linear displacement transducer was used to measure the leaf thickness of sun and shade leaves collected from trees growing in the mountain and eastern coalfield region of Kentucky. Leaf thickness measurements are presented for 64 southern Appalachian forest species which occupy all strata of the forest communities. Leaf thickness varied from 117.1 μm in Hydrangea arborescans to 473.9 μm in Ilex opaca. In all species sun leaves were thicker than shade leaves. Species considered tolerant of shade had significantly thicker sun and shade leaves than intolerant species when shrubs were included. When shrubs were excluded the sun and shade leaves of tolerant species were thinner than sun and and shade leaves of intolerant species. For all species including shrubs, sun leaf thickness for the tolerant, medium, and intolerant classes averaged 220.1, 183.5, and 213.3 μm, respectively. Although there appeared to be differences in leaf thickness between species inhabiting xeric and mesic sites, these differences were not statistically significant. Variation in sun leaf thickness within the genus Quercus ranged from 130.6 μm in Quercus alba to 306.5 μm in Quercus stellata. Shrub species generally had the thickest leaf blades.

In 1972 and 1973 a scanning electron microscope was used to study stomata and cuticular surfaces of shade leaves collected from trees growing in the mountain and eastern coalfield region of Kentucky. Stomatal frequency and size determinations are presented for about 50 southern Appalachian forest species. Stomata varied from 6534/cm2 in Asimina triloba to 90 909/cm2 in Quercus palustris. Mesic species had fewer stomata per unit leaf surface area than xeric species. Stomatal frequency was not related to shade tolerance. The largest stomata (35 microns (μ)) were found in Populus gileadensis while the smallest (5μ) occurred in Quercus coccinea.