Origem e distribuição de epiderme simples, epiderme múltipla, hipoderme e cordões de fibra em diferentes tribos de cyperaceae (Poales)

Abstract

Anatomical characters of leaf blades are often used in taxonomic and phylogenetic studies for the Cyperaceae family, especially those related to the epidermis and hypodermis. However, in mature organs these tissues can present very similar characteristics, being interpreted erroneously, since they have different origins. Therefore, ontogenetic studies are necessary for the correct denomination of epidermis and hypodermis, including fiber strands. In this work the ontogeny of these tissues was studied in 13 taxa belonging to nine tribes of Cyperaceae in order to determine their origin and to establish the appropriate terminology for each tissue. For this, portions of young rhizomes with vegetative apices were fixed in FAA 50, stored in 70% ethanol and included in synthetic resin. Serial cross sections were performed using a rotating microtome, the material stained with toluidine blue and assembled between lamina and coverslip with entellan. The occurrence of unstratified epidermis was verified in the species Cariceae, Cladieae, Cryptangieae, Eleocharideae, Hypolytreae and Sclerieae, whereas in the Abildgaardieae, Cypereae and Rhynchosporeae tribes the occurrence of multiple epidermis was observed. The formation of a continuous hypodermis was observed only in Hypolytreae. The fiber strands originate from the protoderm in most of the species studied, only in Fimbristylis dichotoma was observed the mixed origin of the protoderm and fundamental meristem. Through the obtained data, the number of species with multiple epidermis was increased, being confirmed the occurrence of hypodermis only in the tribe Hypolytreae. In addition, we emphasize that the subepidermal layers, called fiber strands, can not be treated as hypodermis, since they present protodermal origin.