Despite formal separation based on molecular and morphological evidence, the genera Prosthechea Knowles & Westc. and Encyclia Hook. have not been studied in terms of their vegetative anatomy. In this study we examine 16 Brazilian species of these genera. Additionally, one species of subtribe Laeliinae and another from subtribe Oncidiinae were studied in order to evaluate the taxonomic consistency of the anatomic characters observed. Except for Epidendrum crassifolium Lindl., all species possess a velamen differentiated into epivelamen and endovelamen. Endodermal cells with uniformly thickened walls, calcium oxalate raphides and cells with phi thickenings in the cortical region were observed in all species. Silica bodies, raphides and fibre bundles in the mesophyll were common in leaves of all species studied. By contrast, flavonoid crystals were observed in both roots and leaves of Prosthechea only. Encyclia is characterized by the presence of fibre bundles on the subepidermal layer, and a cuticle, which is clearly thicker than that of Prosthechea. These data strongly support the separation of Prosthechea and Encyclia. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 143, 293–303.

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Com o objetivo de estudar a absorção e translocação de Ca, Co, Fe, K e Zn em Aechmea blanchetiana, plantas foram cultivadas in vitro em meios de cultivo contendo concentrações de Zn (0,0; 0,18; 1,8; 18 e 180 mg Zn L-1). Após 16 semanas de cultivo, os sistemas aéreo e radicular foram separados e determinadas à massa seca para massa de matéria seca e para a análise por ativação com nêutrons (AAN). O procedimento consistiu em irradiar amostras e padrões no reator nuclear de pesquisa IEA-R1 por 16 h para análise por espectrometria de raios gama. O controle dos resultados foi avaliado por meio das análises dos materiais de referência certificados, com desvios padrão relativo de 9,1 % e erros inferiores a 12,9 %. Os resultados das determinações dos elementos mostraram que o Zn alterou absorção e translocação de Ca, Co, Fe, K e Zn. A espécie apresentou alta quantidade de Zn nos sistemas aéreo e radicular indicando, possivelmente, ser bioacumuladora desse elemento.

Intermittent water availability characterizes the canopy habitat, but few studies have focused on how C3 epiphytic bromeliads deal with drought. In this context, we investigated how water deficits affect the photosynthetic responses of the epiphytic bromeliad Vriesea gigantea regarding its physiological and anatomical traits that can minimize the effects of stomatal closure. In a controlled experiment in which bromeliads were submitted to 21 days of drought, we demonstrated a reduction in the leaf water content followed by strong reductions in net CO2 exchange and the efficiency of the photochemical system. However, there were increases in the yield of non-photochemical quenching and the activities of hydrophilic antioxidants. We observed substomatal chambers connected with air channels reaching the chlorophyllous parenchyma. Our findings indicate that the low net CO2 exchange and the energy imbalance possibly increased the cyclic transport of electrons and activated the thermal dissipation of energy to avoid damage to the photosynthetic apparatus. Additionally, the aeration channels may passively store CO2 to facilitate its re-assimilation. Because most epiphytic bromeliads are C3 plants and drought is frequent in the canopy, we speculate that some attributes of V. gigantea may occur in other C3 species, favouring their radiation in the epiphytic environment.