Leaf Blade Anatomy of Philippine Medinilla Gaudich. Species in Relation to their Epiphytic Habit

Leaf anatomy of four epiphytic species of Philippine Medinilla , namely, M. magnifica Lindl., M. miniata Merr., M. pendula Merr., and M. teysmannii Miq., was characterized by observation of leaf cross sections prepared through paraffin method. Similarities among the four species revealed by this study include thick hypodermis below the upper epidermis, palisade mesophyll comprising one layer of elongated lignified parenchyma cells, spongy mesophyll with scarce air spaces, and polocytic stomates present only in the lower epidermis. These features aid in water conservation which is highly crucial among epiphytes. Presence of druse crystals in all four species was observed. This feature functions for structural support, defense against herbivory, calcium storage, and increasing photosynthetic efficiency. In hypodermis, number of cell layers, cell shape, and relative thickness vary among the four species in this study. The spongy mesophyll of the four species differ in number of cell layers. Because these variations can differentiate these species from one another, they are deemed to be useful in taxonomy. This study shows that anatomical features of the Medinilla species used in this study are related to their epiphytic nature and their occurrence in the forest understory. Keywords: Medinilla , epiphyte, sclerified mesophyll, hypodermis, druse, polocytic stomates