Aspectos ecoanatómicos de ocho especies de Pentacalia Cass. (Asteraceae) de los Andes venezolanos

Abstract

Pentacalia Cass. is the genus from Asteraceae with more quantity of species in Venezuela and many species are endemic. This genus have a high importance in paramos from venezuelan Andes but are few studies about this genus in Venezuela, specially in relation to wood anatomy and site conditions. This paper is a research about features of xylem conductive elements in eight species of Pentacalia Cass. collected in high mountains of Merida and Tachira states (Venezuela) is presented; with the aim of study ecoanatomical aspects like mesomorphic of xeromorphic type in species collected in zones of paramo and cloudy forest. Samples were prepare using standars procedures of xylem microtechnique and description was made for qualitative (porosity, vessels grouping, vessels arrangement, perforations plates, intervessels pits) and quantitative (frequency and diameter, length element vessels, pits diameter) vessels features according IAWA Committe. Vulnerability and mesomorphic indexes are calculated. Some importants features observed in species studied are: high number of vessels, narrow vessels in diameter, short vessel elements and spiral thickenings in all species studied except in P. reflexa. From an ecoanatomical point of view, vulnerabilty and mesomorphy index shows a xeromorphic type for species of Pentacalia collected in paramo, with conductive elements oriented to safety in conduction of water and mineral salts. P. reflexa, only specie collected in cloudy forest, shows a mesomorphic type.