174 research outputs found
Efeito de doses de nitrogênio em cobertura em variáveis biométricas e de produção em híbridos de milho.
Resumo: Com o objetivo de avaliar a adubação nitrogenada em cobertura em variáveis biométricas e de produção de diferentes híbridos de milho, conduziu-se ensaio em condições de campo em Jaboticabal, SP. Antes da instalação do experimento foi realizada amostragem de solo na camada 0-20 cm para verificação da fertilidade do solo e ainda realizou-se a adubação de semeadura, que consistiu em 300 kg ha-1 do formulado 4-20-20. Os tratamentos foram dois genótipos híbridos simples, AS1522 e AS1596 submetidos a quatro níveis de N em cobertura: zero, metade da padrão, padrão e duas vezes a padrão. O delineamento foi em blocos ao acaso, com três repetições. A semeadura foi realizada manualmente, e quando as plantas atingiram estágio de maturidade fisiológica foram avaliadas as variáveis altura, diâmetro do colmo, produção de grãos, número de grãos por espiga e número de fileiras de grãos por espiga. Os dados foram analisados utilizando-se o teste F e, quando significativos foi realizado teste de comparação de médias. Há diferença entre os híbridos de milho em função das doses de nitrogênio aplicadas em cobertura para produção de grãos e eficiência agronômica. O material AS1596 apresentou superioridade na produção de grãos e eficiência agronômica em relação ao genótipo AS1522. [Effect of nitrogen topdressing levels on biometric variables and on production of corn hybrids]. Abstract: Aiming to evaluate the nitrogen topdressing on biometric variables and production of different corn hybrids, an experiment was conducted under field conditions in Jaboticabal, SP. Before carrying out the experiment, soil sampling in the layer 0-20 cm was performed for soil fertility verification, also it was performed the sowing fertilization, which consisted of the 300 kg ha-1 formulated 4-20-20. The treatments consisted of two simple hybrid genotypes, AS1522 and AS1596, subjected to four nitrogen level: zero, half the standard, standard and twice the standard. The experimental was a randomized complete block design with three replications. The sowing was done manually, and when the plants reached stage of physiological maturity, parameters such as height, stem geometry, grain yield, number of grains per spike and number of grain rows per ear were evaluated. The data were analyzed through the F test, and when significant, it was carried out an average comparison. There is difference between the hybrids on the basis of nitrogen topdressing for grain yield and agronomic efficiency. The material AS1596 showed superiority in grain yield and agronomic efficiency in relation to genotype AS1522
An estimate of the time variation of the O/H radial gradient from planetary nebulae
Radial abundance gradients are a common feature of spiral galaxies, and in
the case of the Galaxy both the magnitude of the gradients and their variations
are among the most important constraints of chemical evolution models.
Planetary nebulae (PN) are particularly interesting objects to study the
gradients and their variations. Owing to their bright emission spectra, they
can be observed even at large galactocentric distances, and the derived
abundances are relatively accurate, with uncertainties of about 0.1 to 0.2 dex,
particularly for the elements that are not synthesized in their progenitor
stars. On the other hand, as the offspring of intermediate mass stars, with
main sequence masses in the interval of 1 to 8 solar masses, they are
representative of objects with a reasonable age span. In this paper, we present
an estimate of the time variation of the O/H radial gradient in a sample
containing over 200 nebulae with accurate abundances. Our results are
consistent with a flattening of the O/H gradient roughly from -0.11 dex/kpc to
-0.06 dex/kpc during the last 9 Gyr, or from -0.08 dex/kpc to -0.06 dex/kpc
during the last 5 Gyr.Comment: 9 pages, 7 encapsulated postscript figures, LaTeX, uses Astronomy and
Astrophysics macro aa.cls, graphicx package, to be published in Astronomy and
Astrophysics (2002), Also available at: http://www.astro.iag.usp.br/~macie
De novo transcriptome assembly of sugarcane leaves submitted to prolonged water-deficit stress.
ABSTRACT. Sugarcane production is strongly influenced by drought, which is a limiting factor for agricultural productivity in the world. In this study, the gene expression profiles obtained by de novo assembly of the leaf transcriptome of two sugarcane cultivars that differ in their physiological response to water deficit were evaluated by the RNA-Seq method: drought-tolerant cultivar (SP81-3250) and drought-sensitive cultivar (RB855453). For this purpose, plants were grown in a greenhouse for 60 days and were then submitted to three treatments: control (-0.01 to -0.015 MPa), moderate water deficit (-0.05 to -0.055 MPa), and severe water deficit (-0.075 to -0.08 MPa). The plants were evaluated 30, 60, and 90 days after the beginning of treatment. Sequencing on an Illumina platform (RNA-Seq) generated more than one billion sequences, resulting in 177,509 and 185,153 transcripts for the tolerant and sensitive cultivar, respectively. These transcripts were aligned with sequences from Saccharum spp, Sorghum bicolor, Miscanthus giganteus, and Arabidopsis thaliana available in public databases. The differentially expressed genes detected during the prolonged period of water deficit permit to increase our understanding of the molecular patterns involved in the physiological response of the two cultivars. The tolerant cultivar differentially expressed a larger number of genes at 90 days, while in the sensitive cultivar the number of differentially expressed genes was higher in 30 days. Both cultivars perceived the lack of water, but the tolerant cultivar responded more slowly than the sensitive cultivar. The latter requires rapid activation of different water-deficit stress response mechanisms for its survival. This rapid activation of metabolic pathways in response to water stress does not appear to be the key mechanism of drought tolerance in sugarcane. There is still much to clarify on the molecular and physiological pattern of plants in response to drought.Article gmr16028845
de novo assembly and transcriptome analysis of sugarcane leaves from contrasting varieties submited to prolonged water stress.
Sugarcane is an important crop, major source of sugar and alcohol, accounting for two-thirds of the world's sugar production. In Brazil, the sugarcane culture has expanded to areas with prolonged drought seasons, which is constraining its production. In order to identify genes and molecular process related to sugarcane drought tolerance, we performed de novo assembly and transcriptome analysis of two sugarcane genotypes, one tolerant and other sensitive to water stress, submitted to three water deficit condition (30, 60 and 90 days). The de novo assembly of leaves transcriptome was performed using short reads from Illumina RNA-Seq platform, which produced more than 1 billion reads, which were assembled into 177,509 and 185,153 transcripts sequences for the tolerant and sensitive cultivars, respectively. These transcripts were aligned with Sorghum bicolor, Miscanthus giganteus, Arabidopsis thaliana sequences and sugarcane sequences available in public databases. This analysis allowed the identification of a set of sugarcane genes shared with other species, as well as led to the identification of novel transcripts not cataloged yet. Differential expression analysis between genotypes and among days of water deficit were performed with EdgeR and DESeq. The differentially expressed genes were annotated and categorized using Blast2GO. The terms "enzyme regulator" and "transcription regulator" were highlighted within the differentially expressed genes between the contrasting cultivars, suggesting the importance of gene regulation during water deficit. This study found new molecular patterns, which provided hypotheses on plant response to drought and provided important information about genes involved in drought tolerance response.PAG 2016. Pôster P0792
In Search of Possible Associations between Planetary Nebulae and Open Clusters
We consider the possibility of cluster membership for 13 planetary nebulae
that are located in close proximity to open clusters lying in their lines of
sight. The short lifetimes and low sample size of intermediate-mass planetary
nebulae with respect to nearby open clusters conspire to reduce the probability
of observing a true association. Not surprisingly, line of sight coincidences
almost certainly exist for 7 of the 13 cases considered. Additional studies are
advocated, however, for 6 planetary nebula/open cluster coincidences in which a
physical association is not excluded by the available evidence, namely M
1-80/Berkeley 57, NGC 2438/NGC 2437, NGC 2452/NGC 2453, VBRC 2 & NGC 2899/IC
2488, and HeFa 1/NGC 6067. A number of additional potential associations
between planetary nebulae and open clusters is tabulated for reference
purposes. It is noteworthy that the strongest cases involve planetary nebulae
lying in cluster coronae, a feature also found for short-period cluster
Cepheids, which are themselves potential progenitors of planetary nebulae.Comment: Accepted for publication in PASP (December 2007
A seven-year study about the negative cloud-to-ground lightning ash characteristics in Southeastern Brazil
Abstract A seven-year study of negative cloud-to-ground (CG) lightning ash characteristics in southeastern Brazil is presented. The study is based on approximately 10 million ashes recorded by a Lightning Position and tracking system lightning detection network from November 1988 to December 1995. The data set is the longest ever obtained in the tropics using an almost constant network conÿguration. It provides a unique opportunity to study the long-term annual, monthly, and local time distributions of the number, intensity (peak current) and multiplicity of negative CG ashes in the tropics. The annual distribution of the number of ashes has variations as large as 80%. The variations does not show any clear relationship with any meteorological parameter, possibly indicating the complex interactions of di erent processes responsible for the lightning activity. The monthly and local time distributions seem to follow closely the related distributions of air temperature. The annual distribution of peak current shows an average value of 40:4 kA and has a signiÿcant decrease from 1991 to 1994, apparently related to an El Niño seasonal e ect. The monthly distribution of peak current shows lower values in the winter, in contrast with the results recently reported for the United States, and seems to be related to the monthly distribution of the number of ashes. The local time distribution of the peak current seems also to be related to the local time distribution of the number of ashes; however, the dependency is less evident. The annual distribution of multiplicity has a systematic decrease during the period, with no apparent relationship with any of the variables studied. The monthly distribution of multiplicity is consistent with the hypothesis that the multiplicity is related to the average height of thunderstorms. The local time distribution of multiplicity, in turn, shows a sunrise/sunset e ect. The results are compared to similar ones obtained in other regions of the world
Effect of cover crops and nitrogen rates on sprinkler irrigated wheat in low altitude cerrado
Host specificity and experimental assessment of the early establishment of the mistletoe Phoradendron crassifolium (Pohl ex DC.) Eichler (Santalaceae) in a fragment of Atlantic Forest in southeast Brazil
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