Anatomical characterization of vegetative organs and scapes of Rondonanthus (Eriocaulaceae, Poales)

Abstract

Eriocaulaceae is a pantropical family and comprises ten genera. Rondonanthus is endemic to the north region of South America and comprises six species. The anatomy of roots, stem, leaves, and scapes were studied in four species to characterize the genus and to identify characteristics with taxonomic value. The following characteristics are diagnostic of Rondonanthus: roots-heterogeneous cortex with an aerenchyma supported by arm cells and vascular cylinder with a central metaxylem vessel element; stems-idioblasts with druses in the cortex and in the pith; leaves-Malpighian hairs, hypodermis in the adaxial surface, chlorenchyma with arm cells, druse idioblasts in the mesophyll, and vascular bundle sheath extensions with rounded cells; scapes-Malpighian hairs and chlorenchyma with arm cells. Rondonanthus capillaceus differed from the remaining studied species by presenting roots with a homogeneous cortex with thinwalled cells; filiform leaves without stomata and trichomes but with a chlorophyllous epidermis and a parenchymatous mesophyll and only one central vascular bundle without sheath extension. Such differences may be related to the habitat, since this species grows on river margins and requires hydrodynamic organs. The number of vascular bundles in the leaves is a useful characteristic to differentiate among species.

Anatomy of vegetative organs, inflorescence axis and pedicel in the Neoregelia bahiana complex (Bromeliaceae): taxonomic and ecological importance

“…The presence of such suberized tissue in the stem has previously been reported for species of Acanthostachys, Aechmea, Ananas, Billbergia, Bromelia L. (Bromelioideae), Dyckia (Pitcairnioideae) and Tillandsia L. (Tillandsioideae) Scatena 2004a, Proença andSajo 2008a), indicating that the short aerial stem probably grows in thickness as well. This growth is probably promoted by the pericycle and/or endodermis (primary thickening meristem), as documented in other monocotyledons (Diggle andDeMason 1983, Menezes et al 2005), including Poales such as Cyperaceae (Rodrigues and Estelita 2009), Eriocaulaceae (Scatena and Menezes 1995, Oriani et al 2008, Oliveira and Oriani 2016 and Rapateaceae (Menezes et al 2005). However, ontogenetic studies are necessary to elucidate the stem structure in Bromeliaceae and its relationship to the different life forms found in the family.…”