Resumo em português A família Bromeliaceae, dentre a grande variedade de plantas tropicais nativas do Brasil, tem merecido destaque devido à sua importância econômica como plantas ornamentais, sendo atualmente muito cultivadas e utilizadas na decoração de interiores e em projetos paisagísticos. Alguns gêneros são endêmicos da Floresta Atlântica e, em função dessa procura, a retirada de seus ambientes naturais constitui ameaça a algumas espécies. A Unidade de Pesquisa e Conserv (mais) ação de Bromeliaceae (UPCB), localizada na Universidade Federal de Viçosa (UFV), MG, tem como finalidade promover a pesquisa em favor da conservação da família Bromeliaceae. Um problema constante na manutenção desse acervo é a infestação por plantas daninhas. Objetivou-se neste trabalho definir as espécies de plantas daninhas críticas no cultivo de bromélias. Foram realizadas visitas semanais, no período de 17 de novembro de 2006 a 17 de janeiro de 2007, para caracterização do comportamento das espécies de plantas daninhas no cultivo de bromélias na UPCB. Após esse período, realizou-se capina manual dos vasos e triagem das espécies daninhas, que foram identificadas e quantificadas. As espécies críticas foram descritas e seus indivíduos férteis depositados no Herbário VIC, do Departamento de Biologia Vegetal, como material testemunha. Realizou-se, também, documentação fotográfica das espécies durante o período de infestação. Foram identificadas duas espécies críticas: brilhantina (Pilea microphylla), com média de seis indivíduos por vaso, e agriãozinho (Cardamine bonariensis), com média de 13 indivíduos por vaso; sete espécies consideradas potencialmente críticas, com destaque para barba-de-falcão (Crepis japonica); e 12 espécies oportunistas. Resumo em inglês The Bromeliaceae family stands out among the great variety of Brazilian native tropical plants because of the economic importance of its ornamental plants, currently widely cultivated and used for indoors decorations and landscape projects. Some genera are endemic to the Atlantic Forest and to meet their great demand, removal from their natural environment has become a threat to some species. The Research and Conservation of Bromeliaceae (UPCB) Unit of the Universidade Fe (mais) deral de Vicosa, in Vicosa, MG promotes research on Bromeliaceae conservation. Weed infestation is a constant problem in the maintenance of this collection. The objective of this work was to define the most critical weeds in bromeliad cultivation. From November 2006 to January 2007, weekly visits were conducted to the collection of bromeliads planted in pots at the UPCB, aiming to characterize the occurrence and behavior of weed species. After this period, the weeds were manually removed from the pots, identified and quantified. The critical weed species were described and their fertile individuals were included in the VIC Herbarium of the Department of Plant Biology, as checks. Photographic documentation of the weeds was also conducted. Two critical species were identified: Pilea microphylla,with around six individuals per pot, and Cardamine bonariensis, with approximately 13 individuals per pot. Seven other species were considered potentially critical, with Crepis japonica being the most important one. Twelve opportunistic species were also identified.
Resumo em inglês The present paper gives some observations on the tumour formation and other abnormalities observed in the interspecific hybrids, Nicotiana glauca x N. Langsdorffii and N. glauca x N. Sanderae. Without entering into a detailed discussion of the literature and the various speculations proposed by Kostoff and Whitaker about the causes of tumour formations or on the relations between "spontaneous" and pathogenic tumours (Kostoff, Levine and others), two new observations are d (mais) escribed. 1) The abnormalities in the two above mentioned hybrids are quite different. As already reported by other authors, the hybrids N. glauca x N. Langsdorffii are initially quite normal and vigorous, while tumours and other proliferations, on the stem, the stem base and the root appear more or less frequently in older plants. Tumours on leaf are rare and flowers are normal (fig. 1,2,7 and 10). The hybrids N. glauca x N. Sanderae are very different from the former. These remain either weak and rachitic, forming early large tumours at the stem base and on the root (fig. 5 and 6 right half). Numerous shoots with more or less normal leaves may arise from these tumours (fig. 11 and 12). Or the plants show an extremely vigorous and abnormal ramification with a number of serial axial shoots developing in each leaf axis (fig. 3 and 4). The leaves are frequently deformed and the flowers exhibit abnormally coloured patches. When crossing N. glauca with F1 (N. Langsdorffii x N. Sanderae) the offspring could clearly be divided into two groups : plants exactly as described for N. glauca x N. Langsdorffii and others which correspond to the types of N. glauca x N. Sanderae. Thus it seems that we are dealing with a monogenic differences, each species, N. Langsdorffii and N. Sanderae, being homozygous for one allele each. These alleles have no phenotypic effect in either pure species, but only in hybrids when combined with the genom of N. glauca. The situation is somewhat similar to the sublethal genes reported in interspecific crosses involving N, longiflora (Brieger, 3) and Crepis tectorum (Hollingshead, 8). Since the hybrids with N. glauca are completely sterile, it cannot be decided whether the genes reported are only modifiers or are actually causing the tumour formation and the other abnormalities. 2) A histological study was made about the origin of stem tumours. The first sign is the activation of cells of the tissues between epidermies and collenchyma. Some cells adjoining other which are dead or dying start to grow and later on to divide, in the manner typical for cells under the action of traumatic hormons (cf. Brieger, 2). Later on the whole region is activated and the cortex layers degenerate. At this stage large tumours may be formed, but as yet without connection with the xylem (fig. 15). Later on the cambium and the secundary medulary rays participate in the irregular development (fig. 13) which finally reaches the medulla. Finally the central cylindre is forced open and the tumours connected with it (fig. 14). Thus tumours formation on the stem is endogeneous and starts from mature cells, not from meristematic cells. 3) Finally an observation is reported, without an attempt to explain it. In the earliest phases of tumours formation in the stem and in cells not participating it, intracellular bodies are observed (fig. 17) with a colourless membrane and on alveolar and highly refractive content. These bodies resemble somewhat cells of fungus such as Chytridiales, but, as already said, their nature is obscure.