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Divergent drivers of leaf trait variation within species, among species, and among functional groups.
Understanding variation in leaf functional traits-including rates of photosynthesis and respiration and concentrations of nitrogen and phosphorus-is a fundamental challenge in plant ecophysiology. When expressed per unit leaf area, these traits typically increase with leaf mass per area (LMA) within species but are roughly independent of LMA across the global flora. LMA is determined by mass components with different biological functions, including photosynthetic mass that largely determines metabolic rates and contains most nitrogen and phosphorus, and structural mass that affects toughness and leaf lifespan (LL). A possible explanation for the contrasting trait relationships is that most LMA variation within species is associated with variation in photosynthetic mass, whereas most LMA variation across the global flora is associated with variation in structural mass. This hypothesis leads to the predictions that (i) gas exchange rates and nutrient concentrations per unit leaf area should increase strongly with LMA across species assemblages with low LL variance but should increase weakly with LMA across species assemblages with high LL variance and that (ii) controlling for LL variation should increase the strength of the above LMA relationships. We present analyses of intra- and interspecific trait variation from three tropical forest sites and interspecific analyses within functional groups in a global dataset that are consistent with the above predictions. Our analysis suggests that the qualitatively different trait relationships exhibited by different leaf assemblages can be understood by considering the degree to which photosynthetic and structural mass components contribute to LMA variation in a given assemblage
Effect of layer charge on chemical and physical properties of synthetic K-fluorine micas
Inheritance of tolerance to Cowpea Mild Mottle Virus in soybean.
Soybean stem necrosis is caused by Cowpea mild mottle virus (CPMMV) and it has been recognized as an emerging and economically important disease in Brazil. No resistant, but only tolerant cultivars have been identified so far, and their genetic control is still unknown. To investigate the inheritance of soybean tolerance to CPMMV, two crosses between tolerant cultivars (BRS 133 x BRSMT Pintado), and between a susceptible (CD 206) and a tolerant cultivar (BRSMT Pintado) were carried out to obtain F2 and F2:3 generations. Quantitative and qualitative analyses applied to the data from greenhouse evaluations showed that there are at least two distinct major genes determining tolerance to CPMMV, one in the soybean cultivar BRS 133 and another in the cultivar BRSMT Pintado, with predominance of additive genetic effects and heritability levels that allow for efficient selection based on early generation means
Identificação e purificação de um vírus de granulose em Spodoptera frugiperda (Lepidoptera, noctuidae).
Identificação e purificação de um vírus da poliedrose nuclear da lagarta Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera Noctuidae).
A lagarta-do-cartucho e considerado uma das principais pragas da cultura do milho e seu controle tem sido feito basicamente pelo uso de inseticidas quimicos. O CNPMS/EMBRAPA considerando as possibilidades de um controle biologico desta praga, tem procurado um virus de granulose. Recentemente isolou-se , a partir de uma lagarta do campo, um virus de poliedrose nuclear (VPN), que tem sido mantido em larvas em condicoes de laboratorio, causando nestas sintomas identicos ao observado no campo. Poliedrose puderam ser purificados a partir de extratos de lagarta infectada atraves de centrifugacao diferencial em um gradiente de densidade de sacarose. Teste de infectividade mostraram que larvas de S. frugiperda, criadas artificialmente, de 3, 6 e 7 dias de idade,alimentadas com suspensoes poliedros, em concentracoes de 2 x 106 ml, tiveram alta taxa de mortalidade (praticamente 100%), exceto as de 7 dias, na menor dose cuja mortandade foi da ordem de 70%. Exames de extratos das lagartas infectadas mostraram a presenca de grande numero de poliedros, mas a identificacao adequada de que se tratava de um virus de poliedrose nuclear, do tipo "multi-enveloped", (MECPN) so pode ser feita atraves de exames de seccoes ultra finas ao microscopio eletronico: nucleos de ectoderma, tecido adiposo e traqueocitos continham grande numero de poliedros e, ocluidas nestes, particulas baciliformes, em geral varias delas envolvidas por um envoltorio comum.Suplemento
Comparative morpho-anatomical studies of the lesions caused by citrus leprosis virus on sweet orange
The leprosis disease shows a viral etiology and the citrus leprosis virus is considered its etiologic agent. The disease may show two types of cytopatologic symptom caused by two virus: nuclear (CiLV-N) and cytoplasmic (CiLV-C) types. The aim of this study was to compare the morpho-anatomical differences in the lesions caused by leprosis virus-cytoplasmic and nuclear types in Citrus sinensis (L.) Osbeck ?Pêra?. Leaf and fruit lesions were collected in Piracicaba/São Paulo (cytoplasmic type) and Monte Alegre do Sul/São Paulo and Amparo/São Paulo (nuclear type). The lesions were photographed and then fixed in Karnovsky solution, dehydrated in a graded ethylic series, embedded in hydroxy-ethyl methacrylate resin (Leica Historesin), sectioned (5?m thick), stained and mounted in synthetic resin. The digital images were acquired in a microscope with digital video camera. Leaf and fruit lesions caused by the two viruses were morphologically distinct. Only the lesion caused by CiLV-N virus presented three well-defined regions. In both lesions there was the accumulation of lipidic substances in necrotic areas that were surrounded by cells with amorphous or droplets protein. Only leaf and fruit lesions caused by CiLV-N virus exhibited traumatic gum ducts in the vascular bundles.Disponivel em: .Acesso em: 18 out. 2010
Ocorrência de um Potyvirus associado ao mosaico da açucena-gigante.
Plants of spider lily (Crinum sp) showing mosaic symptoms were found in Londrina, Paraná. Electron microscopy examinations revealed flexuous rod shaped particles and lamellar inclusion bodies in the cell cytoplasm. RT-PCR products of 2 kb were amplified by a pair of genus specific primers suggesting the association of a potyvirus, being this the first time a virus infection in this host is reported in Brazil
"Enfezamento pálido" e "enfezamento vermelho" na cultura do milho no Brasil Central.
Foi constatada alta incidencia de plantas com sintomas de "Enfezamento Palido" e de "Enfezamento vermelho" em lavouras de milho no Brasil Central. Na mesma area observou-se a presenca de cigarrinha Dalbulus maidis em alta densidade. A presenca de espiroplasma foi confirmada apenas em plantas com sintomas de "Enfezamento Palido", atraves de teste DAS-ELISA. Os resultados da analise por PCR indicaram a presenca de fitoplasma em algumas amostras de plantas com sintomas do "enfezamento Vermelho"
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