Anatomia ecológica da folha e da raiz e aspectos ecofisiológicos de Orchidaceae epífitas de uma campina da Amazônia central

Abstract

Root and leaf ecological anatomy of twenty-five Orchidaceae epiphytic species occurring in the Amazonian campina is related with C 3 and CAM type carbon fixation pathways, spatial distribution and orchid growing management. Furthermore, we propose a descriptive anatomical model for the absorbing roots as well as a classification for fibrovascular bundles, in addition to dividing these species leaf blades into categories and making ecological and evolutionary interpretations. Thereby, we see that Brassavola martiana, Bulbophyllum setigerum, Cattleya eldorado, Encyclia amicta, Encyclia tarumana, Encyclia vespa, Epidendrum compressum, Epidendrum huebneri, Epidendrum sculptum, Epidendrum strobiliferum, Maxillaria tarumaensis and Maxillaria uncata, adopt the CAM pathway in hot and dry periods alternately. They are capable of living in rich light radiation, xeric and/or oligotrophic environments, such as open grassland. In orchid growing, they can do without a rigorous irrigation regime. On the other hand, we see that Bifrenaria longicornis, Encyclia fragrans, Epidendrum nocturnum, Maxillaria sp, Maxillaria camaridii, Maxillaria pauciflora, Maxillaria pendens, Maxillaria rudolfi, Maxillaria villosa, Ornithidium parviflorum, Rudolfiella aurantiaca, Sobralia fragrans and Sobralia macrophylla only present the C 3 fixation pathway with no other alternative in hot and dry seasons. This is offset by the presence of pseudobulbs, varying succulence degrees or leaf strategic loss, and they are well adapted for colonising environments with little light radiation such as, shaded grassland and, in orchid growing they need a more rigorous irrigation regime. The species present several anatomical characters in common, yet, in a differentiated number, which is directly related to xeromorphism, oligotrophism and herbivoria, among others, which together, comprise an evolutionary adaptive syndrome for the Amazonian ecosystems.