Comparative leaf morphology and anatomy of some neotropical Philodendron Schott (Araceae) species

A comparative morphological and anatomical study on the petioles and lamina of 22 taxa (species, subspecies and cultivars) of the genus Philodendron (subgenera Meconostigma, Pteromischum and Philodendron) has been made in order to investigate interspecific differences which may be useful in species identification. All species have bifacial leaves with petioles, amphistomatic with a strongly reduced density of stomata on the adaxial leaf surface. The species differ in the size and shape of their epidermal cells, the distribution and types of stomata and cuticle ornamentation in the lamina, thickness of epicuticular layer, presence or absence of hypodermis, structure of spongy mesophyll, thickness of palisade and spongy mesophyll layers, as well as types of raphides, and in the structure and forms of petioles. A combination of these characters may be useful in species identification. This study shows that there is some variation in petiole and leaf morphological and anatomical characters among the 22 taxa of Philodendron. However, many characters are present in all of them and may be typical of the genus. The study revealed several detailed interesting epidermal and anatomical features that have not previously been reported in the genus.