The odd roots of Campylocentrum (Angraeciinae-Orchidaceae): an anatomical study of its morphologically variable roots

Abstract Although some anatomical studies have been performed in Angraecinae, knowledge about the anatomy of the genus Campylocentrum is as yet incipient. The aim of this study is to anatomically characterize the structure of the different kinds of roots in the genus. Roots from 12 species were analyzed, including all the morphological variation in the genus (smooth and granulose surface). The leafless species are characterized by endovelamen, exodermal and endodermal cell walls thicker than in the leafy species. The species with terete leaves can be split in two groups: one constituting C. poeppigii, whose roots have a granulose surface produced by numerous unicellular, absorbent hairs; the second formed by six species from the Atlantic Forest. In this second group, the same granulose root appearance is produced by tufts of epivelamen in addition to the unicellular, absorbent root hairs. The other species in the genus, with conduplicate leaves, do not present a pattern for grouping. Some of them, such as C. serranum and C. micranthum, share a similar structure with the leafless species, but with thinner exodermal and endodermal cell walls. Other species, such as C. crassirhizum and C. jamaicense, are the only ones in the genus with ○-thickened cells in the exodermis.