998 resultados para Stele (Botany)


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Mandioca cultivar BRS Purus: origem, adaptação, características botânica e agronômica, recomendações técnicas e produtividade, em Manaus-AM.

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Informacoes sobre o cultivo da graviola envolvendo: clima, solo, descricao botanica, variedades, propagacao, procedimentos para obtencao de mudas, preparo da area e plantio definitivo, tratos culturais (poda, capina, adubacao, doencas, pragas), floracao, frutificacao, producao, colheita, comercializacao, coeficiente tecnico, em Manaus-AM (Brasil).

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J. H. Macduff and A. K. Bakken. (2003). Diurnal variation in uptake and xylem contents of inorganic and assimilated N under continuous and interrupted N supply to Phleum pratense and Festuca pratensis. Journal of Experimental Botany, 54 (381) pp.431-444 Sponsorship: BBSRC / Norwegian Crop Research Institute RAE2008

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J. A. Gallagher, A. J. Cairns and C. J. Pollock (2004). Cloning and characterization of a putative fructosyltransferase and two putative invertase genes from the temperate grass Lolium temulentum L. Journal of Experimental Botany, 55 (397) pp.557-569 Sponsorship: BBSRC RAE2008

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Kingston-Smith, A. H., Bollard, A. L., Humphreys, M. O,, Theodorou, M. K. (2002). An assessment of the ability of the stay-green phenotype in Lolium species to provide an improved protein supply for ruminants. Annals of Botany, 89(6), 731-740. Sponsorship: BBSRC/MAFF/Milk Development Council/Meat and Livestock Commission/Industry. RAE2008

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Macduff, J. H., Humphreys, M. O., Thomas, Howard (2002). Effects of a stay-green mutation on plant nitrogen relations in Lolium perenne during N starvation and after defoliation. Annals of Botany, 89 (1), 11-21. Sponsorship: BBSRC RAE2008

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Plant galls constitute a branch of study and research which has been to me a subject of much interest for some time. At the start of this work, it was intended to include Plant galls in general, but after some months this was found to be too comprehensive a field and would in fact take a great many years to study fully. Even leaf galls alone, both of herbs and trees provide so large a field of investigation that ultimately I decided to confine my attention to those or our native trees and shrubs. Upon looking up the literature on this subject, it will be found that in nearly all cases, either the gall is described fully and mere mention made or the agent concerned in its production, or vice versa. This state of things is most unsatisfactory, as in studying galls, both the gall-maker and the gall formation must be examined in detail before it is safe to apply nomenclature. This work, therefore, sets out to give accurate and scientific descriptions of both galls and gall-makers. The difficulties encountered are manifold; firstly, our trees are all deciduous, hence, the collecting period is necessarily restricted to that time of the year between the appearance of the buds and the fall of the leaf. Secondly, the rearing of imagines is always difficult, especially in the case or the autumn gall; more will be said on this matter later. Lastly, due to war-time conditions much trouble was experienced in obtaining suitable literature and many invaluable books on this subject were unprocurable. The Plates at the back have all been copied from original material except in the case or the Phytoptid mites which have been sketched with the help of illustrations, the reason for this being the difficulty of making suitable mounts of these minute creatures, Where possible all stages or at least larva and imago have been sketched, together with the host plant and the type of gall-formation produced. Slides have also been made of most larvae and the imagines attached to cards and pinned on to pith or cork in the usual manner.

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UNLABELLED: PREMISE OF THE STUDY: The Sphagnopsida, an early-diverging lineage of mosses (phylum Bryophyta), are morphologically and ecologically unique and have profound impacts on global climate. The Sphagnopsida are currently classified in two genera, Sphagnum (peat mosses) with some 350-500 species and Ambuchanania with one species. An analysis of phylogenetic relationships among species and genera in the Sphagnopsida were conducted to resolve major lineages and relationships among species within the Sphagnopsida. • METHODS: Phylogenetic analyses of nucleotide sequences from the nuclear, plastid, and mitochondrial genomes (11 704 nucleotides total) were conducted and analyzed using maximum likelihood and Bayesian inference employing seven different substitution models of varying complexity. • KEY RESULTS: Phylogenetic analyses resolved three lineages within the Sphagnopsida: (1) Sphagnum sericeum, (2) S. inretortum plus Ambuchanania leucobryoides, and (3) all remaining species of Sphagnum. Sister group relationships among these three clades could not be resolved, but the phylogenetic results indicate that the highly divergent morphology of A. leucobryoides is derived within the Sphagnopsida rather than plesiomorphic. A new classification is proposed for class Sphagnopsida, with one order (Sphagnales), three families, and four genera. • CONCLUSIONS: The Sphagnopsida are an old lineage within the phylum Bryophyta, but the extant species of Sphagnum represent a relatively recent radiation. It is likely that additional species critical to understanding the evolution of peat mosses await discovery, especially in the southern hemisphere.

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UNLABELLED: PREMISE OF THE STUDY: The Frullania tamarisci complex includes eight Holarctic liverwort species. One of these, F. asagrayana, is distributed broadly throughout eastern North America from Canada to the Gulf Coast. Preliminary genetic data suggested that the species includes two groups of populations. This study was designed to test whether the two groups are reproductively isolated biological species. • METHODS: Eighty-eight samples from across the range of F. asagrayana, plus 73 samples from one population, were genotyped for 13 microsatellite loci. Sequences for two plastid loci and nrITS were obtained from 13 accessions. Genetic data were analyzed using coalescent models and Bayesian inference. • KEY RESULTS: Frullania asagrayana is sequence-invariant at the two plastid loci and ITS2, but two clear groups were resolved by microsatellites. The two groups are largely reproductively isolated, but there is a low level of gene flow from the southern to the northern group. No gene flow was detected in the other direction. A local population was heterogeneous but displayed strong genetic structure. • CONCLUSIONS: The genetic structure of F. asagrayana in eastern North America reflects morphologically cryptic differentiation between reproductively isolated groups of populations, near-panmixis within groups, and clonal propagation at local scales. Reproductive isolation between groups that are invariant at the level of nucleotide sequences shows that caution must be exercised in making taxonomic and evolutionary inferences from reciprocal monophyly (or lack thereof) between putative species.

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Arabidopsis halleri is a model plant for Zn and Cd hyperaccumulation. The objective of this study was to determine the relationship between the chemical forms of Cd, its distribution in leaves, and Cd accumulation and tolerance. An interspecific cross was carried out between A. halleri and the non-tolerant and non-hyperaccumulating relative A. lyrata providing progenies segregating for Cd tolerance and accumulation. Cd speciation and distribution were investigated using X-ray absorption spectroscopy and microfocused X-ray fluorescence. In A. lyrata and non-tolerant progenies, Cd was coordinated by S atoms only or with a small contribution of O groups. Interestingly, the proportion of O ligands increased in A. halleri and tolerant progenies, and they were predominant in most of them, while S ligands were still present. Therefore, the binding of Cd with O ligands was associated with Cd tolerance. In A. halleri, Cd was mainly located in the xylem, phloem, and mesophyll tissue, suggesting a reallocation process for Cd within the plant. The distribution of the metal at the cell level was further discussed. In A. lyrata, the vascular bundles were also Cd enriched, but the epidermis was richer in Cd as compared with the mesophyll. Cd was identified in trichomes of both species. This work demonstrated that both Cd speciation and localization were related to the tolerance character of the plant.

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p.3-10

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Argumentation as reflected in a short communication from the published literature of botany and zoology is discussed. Trying to capture the logic structure of the argument, however imperfectly, is relevant to information science and depends on a particular goal: namely, to potentially benefit the task of sketching the relationship between bibliographic entries in a better manner than is possible with present-day bibliometric or scientometric practice. This imposes tight limits on the depth of analysis of the text.

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Pollen, microscopic charcoal, palaeohydrological and dendrochronological analyses are applied to a radiocarbon and tephrochronologically dated mid Holocene (ca. 8500–3000 cal B.P.) peat sequence with abundant fossil Pinus (pine) wood. The Pinus populations on peat fluctuated considerably over the period in question. Colonisation by Pinus from ca. 7900–7600 cal B.P. appears to have had no specific environmental trigger; it was probably determined by the rate of migration from particular populations. The second phase, at ca. 5000–4400 cal B.P., was facilitated by anthropogenic interference that reduced competition from other trees. The pollen record shows two Pinus declines. The first at ca. 6200–5500 cal B.P. was caused by a series of rapid and frequent climatic shifts. The second, the so-called pine decline, was very gradual (ca. 4200–3300 cal B.P.) at Loch Farlary and may not have been related to climate change as is often supposed. Low intensity but sustained grazing pressures were more important. Throughout the mid Holocene, the frequency and intensity of burning in these open Pinus–Calluna woods were probably highly sensitive to hydrological (climatic) change. Axe marks on several trees are related to the mid to late Bronze Age, i.e., long after the trees had died.