958 resultados para vegetative tiller


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Overland rain retrieval using spaceborne microwave radiometer offers a myriad of complications as land presents itself as a radiometrically warm and highly variable background. Hence, land rainfall algorithms of the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) have traditionally incorporated empirical relations of microwave brightness temperature (Tb) with rain rate, rather than relying on physically based radiative transfer modeling of rainfall (as implemented in the TMI ocean algorithm). In this paper, sensitivity analysis is conducted using the Spearman rank correlation coefficient as benchmark, to estimate the best combination of TMI low-frequency channels that are highly sensitive to the near surface rainfall rate from the TRMM Precipitation Radar (PR). Results indicate that the TMI channel combinations not only contain information about rainfall wherein liquid water drops are the dominant hydrometeors but also aid in surface noise reduction over a predominantly vegetative land surface background. Furthermore, the variations of rainfall signature in these channel combinations are not understood properly due to their inherent uncertainties and highly nonlinear relationship with rainfall. Copula theory is a powerful tool to characterize the dependence between complex hydrological variables as well as aid in uncertainty modeling by ensemble generation. Hence, this paper proposes a regional model using Archimedean copulas, to study the dependence of TMI channel combinations with respect to precipitation, over the land regions of Mahanadi basin, India, using version 7 orbital data from the passive and active sensors on board TRMM, namely, TMI and PR. Studies conducted for different rainfall regimes over the study area show the suitability of Clayton and Gumbel copulas for modeling convective and stratiform rainfall types for the majority of the intraseasonal months. Furthermore, large ensembles of TMI Tb (from the most sensitive TMI channel combination) were generated conditional on various quantiles (25th, 50th, 75th, and 95th) of the convective and the stratiform rainfall. Comparatively greater ambiguity was observed to model extreme values of the convective rain type. Finally, the efficiency of the proposed model was tested by comparing the results with traditionally employed linear and quadratic models. Results reveal the superior performance of the proposed copula-based technique.

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Woody tree species in seasonally dry tropical forests are known to have traits that help them to recover from recurring disturbances such as fire. Two such traits are resprouting and rapid post-fire growth. We compared survival and growth rates of regenerating small-sized individuals (juveniles) of woody tree species after dry season fire (February-March) at eight adjacent pairs of burnt and unburnt transects in a seasonally dry tropical forest in southern India. Juveniles were monitored at 3-mo intervals between August 2009 and August 2010. High juvenile survivorship (>95%) was observed in both burnt and unburnt areas. Growth rates of juveniles, analyzed at the community level as well as for a few species individually (especially fast-growing ones), were distinctly higher in burnt areas compared to unburnt areas after a fire event, particularly during the pre-monsoon season immediately after a fire. Rapid growth by juveniles soon after a fire may be due to lowered competition from other vegetative forms such as grasses, possibly aided by the availability of resources stored belowground. Such an adaptation would allow a juvenile bank to be retained in the understory of a dry forest, from where individuals can grow to a possible fire-tolerant size during favorable conditions.

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In the current paper, we have primarily addressed one powerful simulation tool developed during the last decades-Large Eddy Simulation (LES), which is most suitable for unsteady three-dimensional complex turbulent flows in industry and natural environment. The main point in LES is that the large-scale motion is resolved while the small-scale motion is modeled or, in geophysical terminology, parameterized. With a view to devising a subgrid-scale(SGS) model of high quality, we have highlighted analyzing physical aspects in scale interaction and-energy transfer such as dissipation, backscatter, local and non-local interaction, anisotropy and resolution requirement. They are the factors responsible for where the advantages and disadvantages in existing SGS models come from. A case study on LES of turbulence in vegetative canopy is presented to illustrate that LES model is more based on physical arguments. Then, varieties of challenging complex turbulent flows in both industry and geophysical fields in the near future-are presented. In conclusion; we may say with confidence that new century shall see the flourish in the research of turbulence with the aid of LES combined with other approaches.

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Los pacientes en estado vegetativo permanente representan un dilema ético en términos de atención médica. El problema está instalado en la sociedad desarrollando un importante dilema que implica la justicia, la religión, la economía y la familia. En el presente trabajo se analiza esta problemática de acuerdo con el “principio de lo éticamente adecuado en el uso de los medios de conservación de la vida”, desarrollado por el profesor M. Calipari. Se presentarán varios casos clínicos que serán analizados a través de esta teoría complementada con aspectos médicos y judiciales, según la legislación argentina.

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Investigation on the effects of explosive shock on marine life. Necessary that the "commercial" effects, the actual damage to commercially important stocks of fish and shellfish, be evaluated. Equally important are the "biological" effects, the immediate physical effects of shock waves on animals and the indirect effects on future stocks. Indirect effects might include the diversion of migratory stocks from an area, or actual damage to the habitat, rendering it unfit for sedentary or non-migratory native species. Interruption of the food chains in an area by destruction of forge forms or vegetation. (PDF contains 43 pages)

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Ao longo do século XX, poucos estudos de dendrocronologia foram desenvolvidos com espécies de ambientes tropicais, em função da crença de que as condições climáticas nessas regiões não apresentavam variações suficientemente marcantes e regulares para induzir um ritmo anual de crescimento radial. A realização de trabalhos sobre esse tema nas últimas décadas revelou que a formação de anéis de crescimento anuais nos trópicos pode estar associada a fatores diversos, como: existência de estação seca bem definida, ocorrência de inundações sazonais, respostas ao comportamento fenológico, respostas ao fotoperíodo e a ritmos endógenos. O presente estudo tem por objetivo compreender a dinâmica de crescimento radial de uma espécie da Mata Atlântica se desenvolvendo em ambiente natural. Para tanto, propôs-se: i) investigar a periodicidade da atividade cambial e dos fatores que a influenciam; ii) estimar a idade e taxa de crescimento diamétrico e iii) correlacionar os fatores ambientais com os anéis de crescimento, em indivíduos de Cedrela odorata L. Para o estudo da atividade cambial, foram obtidas amostras de caule a 1,30 m do solo, contendo periderme, faixa cambial e xilema e floema secundários, por métodos não destrutivos. A fenologia vegetativa e a frutificação dos indivíduos amostrados foram acompanhadas durante todo o período do experimento. O material coletado foi processado segundo técnicas usuais em Anatomia Vegetal e analisado sob microscopia óptica e de fluorescência. Os dados de fotoperíodo, precipitação, temperatura e fenologia vegetativa foram correlacionados à atividade cambial. Para o estudo dos anéis de crescimento, as coletas também foram realizadas a 1,30 m do solo, por meio de sonda de Pressler. As amostras obtidas foram polidas e analisadas sob microscópio estereoscópio, para demarcação e aferição do número de anéis de crescimento, e a largura dos anéis foi mensurada para a determinação das taxas de crescimento radial. A série histórica de temperatura e precipitação foi correlacionada à cronologia dos anéis de crescimento. Os resultados indicaram que a atividade cambial segue um ritmo anual de crescimento, correlacionado à sazonalidade do fotoperíodo, da precipitação e da fenologia vegetativa. A análise dos anéis de crescimento permitiu estimar a idade dos indivíduos e determinar a taxa média de incremento e as taxas de incremento diamétrico acumulado e incremento médio anual para a espécie no sítio de estudo. Os dados de incremento radial evidenciaram a ausência de relação entre a idade e o diâmetro das árvores. A análise da variação na largura dos anéis não apresentou correlações significativas com os fatores climáticos analisados.

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A major survey of the River Endrick was carried out in 1959-60. This survey was repeated three decades later in 1989-90 and comparisons were made of the fauna at the two times of sampling. During both surveys, photographs were taken of all the sampling sites and the objective of the present paper is to compare some of these photographs and discuss the value of photography in studies of river ecology. The sites used for photographic comparison were not chosen originally for that purpose but as appropriate places on the river from source to mouth to study its ecology. The pairs of photos now available have proved of interest and value and some lessons have been learned in relation to the selection of sites for any future photographic studies. Ideally photos should be taken in more than one season of the year as much of the river can be obscured by riparian trees and shrubs during the vegetative season. The exact position from which each photograph is taken is also a major factor to be considered.

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Representatives from the family of Lemnaceae (duckweed) make ideal experimental material for research into a succession of phytophysiological processes with regard to growth rate and vegetative reproduction. They are also easy to maintain in sterile cultures. Lemnaceae belong to the higher flowering plants (flowers are rarely produced), however they are distinguished by a much simplified morphological and anatomical structure. As water plants they possess the advantage, that they can be cultivated in synthetic media under laboratory conditions controlled by the application of both a known light intensity and temperature. This paper describes experimental research of growth of Lemnaceae in different conditions. Some of the variables were mineral media, illumination and aeration.

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The purpose of this work was the study of phytoplankton production of the salt lakes of the Steppe region of Crimea, during the vegetative period of 1974. From May to October Sakskoe and Sasyk Lakes were examined, and from August to October - Moinakskoe Lake. The density of the salt water was measured and the intensity of photosynthesis was determined. From the data presented, it is apparent that the intensity of photosynthesis in Sakskoe and Sasyk Lakes, on average, is extremely high.

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The process of prophage integration by phage λ and the function and structure of the chromosomal elements required for λ integration have been studied with the use of λ deletion mutants. Since attφ, the substrate of the integration enzymes, is not essential for λ growth, and since attφ resides in a portion of the λ chromosome which is not necessary for vegetative growth, viable λ deletion mutants were isolated and examined to dissect the structure of attφ.

Deletion mutants were selected from wild type populations by treating the phage under conditions where phage are inactivated at a rate dependent on the DNA content of the particles. A number of deletion mutants were obtained in this way, and many of these mutants proved to have defects in integration. These defects were defined by analyzing the properties of Int-promoted recombination in these att mutants.

The types of mutants found and their properties indicated that attφ has three components: a cross-over point which is bordered on either side by recognition elements whose sequence is specifically required for normal integration. The interactions of the recognition elements in Int-promoted recombination between att mutants was examined and proved to be quite complex. In general, however, it appears that the λ integration system can function with a diverse array of mutant att sites.

The structure of attφ was examined by comparing the genetic properties of various att mutants with their location in the λ chromosome. To map these mutants, the techniques of heteroduplex DNA formation and electron microscopy were employed. It was found that integration cross-overs occur at only one point in attφ and that the recognition sequences that direct the integration enzymes to their site of action are quite small, less than 2000 nucleotides each. Furthermore, no base pair homology was detected between attφ and its bacterial analog, attB. This result clearly demonstrates that λ integration can occur between chromosomes which have little, if any, homology. In this respect, λ integration is unique as a system of recombination since most forms of generalized recombination require extensive base pair homology.

An additional study on the genetic and physical distances in the left arm of the λ genome was described. Here, a large number of conditional lethal nonsense mutants were isolated and mapped, and a genetic map of the entire left arm, comprising a total of 18 genes, was constructed. Four of these genes were discovered in this study. A series of λdg transducing phages was mapped by heteroduplex electron microscopy and the relationship between physical and genetic distances in the left arm was determined. The results indicate that recombination frequency in the left arm is an accurate reflection of physical distances, and moreover, there do not appear to be any undiscovered genes in this segment of the genome.

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The advent of molecular biology has had a dramatic impact on all aspects of biology, not least applied microbial ecology. Microbiological testing of water has traditionally depended largely on culture techniques. Growing understanding that only a small proportion of microbial species are culturable, and that many microorganisms may attain a viable but non-culturable state, has promoted the development of novel approaches to monitoring pathogens in the environment. This has been paralleled by an increased awareness of the surprising genetic diversity of natural microbial populations. By targeting gene sequences that are specific for particular microorganisms, for example genes that encode diagnostic enzymes, or species-specific domains of conserved genes such as 16S ribosomal RNA coding sequences (rrn genes), the problems of culture can be avoided. Technical developments, notably in the area of in vitro amplification of DNA using the polymerase chain reaction (PCR), now permit routine detection and identification of specific microorganisms, even when present in very low numbers. Although the techniques of molecular biology have provided some very powerful tools for environmental microbiology, it should not be forgotten that these have their own drawbacks and biases in sampling. For example, molecular techniques are dependent on efficient lysis and recovery of nucleic acids from both vegetative forms and spores of microbial species that may differ radically when growing in the laboratory compared with the natural environment. Furthermore, PCR amplification can introduce its own bias depending on the nature of the oligonucleotide primers utilised. However, despite these potential caveats, it seems likely that a molecular biological approach, particularly with its potential for automation, will provide the mainstay of diagnostic technology for the foreseeable future.

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O conhecimento sobre o ritmo de crescimento radial e a idade das árvores é um aspecto básico para compreender a dinâmica das populações, bem como o desenvolvimento e a sobrevivência das espécies. Nos trópicos, entretanto, estudos populacionais com este enfoque ainda são escassos, a despeito da urgente necessidade de preservação e manejo de suas florestas. Este trabalho tem por objetivo: i) Descrever a atividade cambial e o comportamento fenológico de Centrolobium robustum (Vell.) Mart. ex Benth., correlacionando estes parâmetros entre si; ii) Avaliar a influência da sazonalidade climática e do fotoperíodo sobre a atividade cambial e o comportamento fenológico e iii) Caracterizar o padrão estrutural dos anéis de crescimento e determinar, a partir destes, a idade e as taxas de crescimento radial da espécie na Reserva Biológica do Tinguá, RJ. Para a análise da atividade cambial, amostras de câmbio foram coletadas trimestralmente, processadas segundo técnicas usuais de anatomia vegetal e observadas sob microscopia ótica de campo claro, de fluorescência, de polarização e microscopia eletrônica de transmissão. O acompanhamento fenológico foi realizado mensalmente e os índices de atividade e de intensidade foram utilizados para analisar as fenofases reprodutivas e vegetativas, respectivamente. Para a investigação dendrocronológica, foram coletadas amostras com auxílio de sonda de Pressler, as quais foram polidas e observadas sob microscópio estereoscópico. Os resultados evidenciaram um ciclo anual de atividade e dormência cambial, caracterizados, respectivamente, pela presença de células em processo de divisão e diferenciação junto ao câmbio e de células completamente diferenciadas e deposição de calose em elementos de tubo crivado adjacentes à zona cambial. A dormência cambial coincidiu com a senescência e queda foliar, enquanto a atividade foi mais evidente na presença de folhas adultas na copa. A sazonalidade da atividade cambial apresentou correlação significativa com os dados de temperatura, precipitação e fotoperíodo do mês de realização das coletas. Foi constatado o regime sazonal da atividade cambial em associação ao clima e ao comportamento fenológico da espécie, conferindo caráter anual aos anéis de crescimento. Os resultados permitiram estabelecer o padrão dendroecológico de C. robustum e as idades e taxas de crescimento da população estudada.

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Contemporary striped bass population modeling efforts on coastal stocks point to a reduced population fecundity in Chesapeake Bay being partially responsible for declining reproduction (Anonymous 1985; Boreman and Goodyear 1984). Fecundity values used in these models were based on earlier work by jackson and tiller (1952), lewis and Bonner (1966), Hollis (1967) and Holland and Yelverton (1973). An important feature to the Boreman and Goodyear (1985) model (FSIM) is an accurate determination of the fecundity weight regression equation used to determine the rate of egg deposition over time. Egg deposition models in turn can be used to determine how reproductive potential is changing over time in response to various management actions, i.e. reducing fishing mortality rates. thus it is imperative to follow population stock structure in the Bay system and to develop a contemporary fecundity relationship for striped bass. This report deals with the gonadal material collected in 1986 and 1987 from a coordinated Maryland field program. Samples were obtained from drift gill net collections during the spawning season from four localities: Potomac Estuary, Upper Bay, Chesapeake and Delaware Canal, and the Choptank Estuary (Figure 1).

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Este estudo tem por objetivo ampliar o conhecimento sobre a flora da Ilha Grande, Angra dos Reis, RJ, através da avaliação florística e fitossociológica da comunidade arbustivoarbórea, com Circunferência à Altura do Peito ≥ 15,7 cm (CAP ≥ 5,0 cm) em trechos de Floresta Atlântica montana. Foram alocadas 34 parcelas retangulares e permanentes de 10x30 m, totalizando uma área amostral de 1,02 ha. Foram amostrados todos os indivíduos arbustivoarbóreos vivos, que tiveram aferidas a circunferência do caule, estimada a altura total, altura do fuste e realizada a coleta de material botânico. A identificação dos espécimes foi realizada através da análise das estruturas vegetativas e reprodutivas, comparação em herbários, consultas a literatura especializada e, quando possível, com auxílio de especialistas. O material botânico coletado está sendo incorporado à coleção do Herbário da Universidade do Estado do Rio de Janeiro (HRJ). Procedeu-se a avaliação do status de conservação das espécies determinadas para identificar o grau de ameaça. A estrutura da comunidade inventaria foi analisada através do pacote estatístico FITOPAC 2.1. Inventariou-se 1.847 indivíduos arbustivo-arbóreos vivos, subordinados a 225 espécies ou morfo-espécies de 27 gêneros e 53 famílias botânicas. Este estudo constatou que a Ilha Grande é uma nova área de ocorrência para 53 espécies fanerogâmicas. As famílias mais abundantes foram: Myrtaceae (391 indivíduos), Rubiaceae (337), Euphorbiaceae (100), Fabaceae (84) e Sapotaceae (72). Myrtaceae (69 spp.), Rubiaceae (14), Fabaceae (13), Lauraceae e Sapotaceae (11) foram as famílias que apresentaram as maiores riquezas. O índice de diversidade de Shannon & Weaver (H) obtido foi de 4,609 nats/indvs. e o de equabilidade (J) de 0,851. Os parâmetros fitossociológicos calculados indicaram que Amaioua intermedia Mart. (5,17%), Eriotheca pentaphylla (Vell.) A. Robyns (4,84%), Qualea glaziovii Warm. (2,74%), Vochysia bifalcata Warm. (2,69%), Xylopia brasiliensis Spreng. (2,48%), Heisteria silvianii Schwacke (2,43%), Coussarea nodosa (Benth.) Müll. Arg. (2,38%), Guapira opposita (Vell.) Reitz (2,37%), Manilkara subsericea (Mart.) Dubard (2,02%) e Inga lanceifolia Benth. (1,86%) são as espécies com maiores Valores de Importância (VI). Entre as táxons inventariados foi possível identificar 69 espécies raras, representadas na comunidade por um único indivíduo, e nove espécies com problemas de conservação, dais quais Chrysophyllum flexuosum Mart., Micropholis crassipedicellata (Mart. & Eichler ex Miq.) Pierre e Manilkara subsericea (Mart.) Dubard estão categorizadas como dependentes de conservação; Eugenia prasina O. Berg como vulnerável; Myrceugenia myrcioides (Cambess.) O.Berg como futuramente ameaçada de extinção; Ocotea odorifera Rohwer como ameaçada de extinção e/ou vulnerável a extinção; Pradosia kuhlmannii Toledo como ameaçada de extinção; Solanum carautae Carvalho como espécie rara e Urbanodendron bahiense (Meisn.) Rohwer em perigo de extinção. A distribuição dos indivíduos em classes diamétricas apresentou uma tendência exponencial negativa, sugerindo que a comunidade possui capacidade de autoregeneração. Os resultados da composição florística e da estrutura da vegetação montana do PEIG evidenciaram expressiva riqueza e diversidade de espécies arbóreas, cuja preservação é fundamental para o funcionamento e o equilíbrio desta formação. Palavras-chave: Mata Atlântica. Floresta montana. Fitossociologia. Parque Estadual da Ilha Grande.

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The toxicity of the herbicide glyphosate was tested on water hyacinth (Eichhornia crassipes) samples cultivated in glass aquariums. The lowest dose (0.09 g.m-2) leads to an increasing plant growth rate. This growth rate decreases with intermediate doses (0.18 and 0.36 g.m-2), the consequence of which is to increase stolons (vegetative reproduction). On the other hand, the dose of 0.72 g.m-2 leads to a total and irreversible destruction of plants.