Do anatomical traits converge on epiphytic plants?

Abstract

Epiphytes represent approximately 10% of vascular plants, or 25,000 species distributed across 84 families. Water deficit is the greatest challenge faced by epiphytes, resulting in anatomical strategies aimed at maximizing water usage and minimizing water loss. This study aimed to characterize the leaf blade anatomy of 40 species of vascular epiphytes occurring in a cloud forest of the Brazilian Atlantic Forest and assess how leaf anatomy is related to the epiphytic life form. Samples were collected, fixed, dehydrated with ethanol, and embedded in paraffin for sectioning using a microtome or freehand technique. Some samples were dissociated for epidermal observation. A clustering analysis (using UPGMA) was conducted using a presence/absence matrix of 16 anatomical characters. The results showed that species within this functional group exhibit different leaf blade anatomical characteristics, which may or may not be adaptive to epiphytism. However, despite the occurrence of some characteristics such as stomata at the same level as other epidermal cells, thick cuticle, fibers, hypodermis, and homogeneous chlorophyllous parenchyma in 50% or more of the species, there is no set of anatomical characteristics that can be used to define an epiphyte.

Key words:
dwarf cloud forest; ecological anatomy; epiphytism; water deficit.