Características morfológicas y arquitecturales de las especies de Nothofagus Blume (Fagaceae) del Norte de la Patagonia Argentina

International audienceMorphological and architectural features of Nothofagus antarctica (G. Forster) Oersted, N. dombeyi (Mirb.) Blume, N. pumilio (Poepp. et Endl.) Krasser, N. obliqua (Mirb.) Blume and N. nervosa (Phil.) Dim. et Mil. were studied in their natural habitat. Except for the two leaves following the cotyledons, which may be opposite, leaves are normally alternate and distichously arranged along the stem, although tristichous arrangement is not rare in all species but N. pumilio. The basic structure of a leaf includes a petiolated blade and two stipules; the degree of development of each of these parts depends on the leaf position on the plant. Compared to known related species from the northern hemisphere, buds in Nothofagus spp. have low numbers of cataphylls; this kind of leaf may be absent in terminal buds. A shoot elongated during one growing season may or may not branch in that season, which depends on shoot vigour and shoot-apex persistence. The apex of an annual shoot may persist after shoot elongation but spontaneous apex death is relatively common. Flowers are preformed in the winter bud together with their bearing shoot. Morphological and architectural features of the species of Nothofagus studied here are more similar to those of studied species of Fagus, Alnus and Carpinus than to those of Quercus