XVI International Botanical Congess

This study compared epidermal characters of sun/shade Pentaclethra macroloba leaflets to stream debris leaflets at La Selva Biological Station in Costa Rica. Characters analyzed are stomatal position and size, epidermal cell form and size, trichomes, as well as stomatal and epidermal cell density and the Stomatal Index (SI) for leaflets from these different sources. Stomatal density is 2.6 more per area in the sun (high canopy) than in the shade (ground level) while differences in epidermal cell densities were 1.6 more in the sun. Often the SI will even out these differences but here we found a SI of 5.4 in the shade and a SI of 8.4 for the sun leaflets. This may reflect differences in CO2 concentrations for the microhabitats in which these leaflets developed. The debris leaflets appear to consist of both sun and shade leaflets as determined by their SI.