946 resultados para Plantas - Efeito da sombra


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Pós-graduação em Ciência Animal - FMVA

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Pós-graduação em Ciências Biológicas (Botânica) - IBB

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Pós-graduação em Agronomia (Energia na Agricultura) - FCA

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Pós-graduação em Agronomia (Horticultura) - FCA

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The use of plants to treat diseases or even to cure them is a high diffused popular tradition, and several studies discuss the therapeutic and pharmacological properties of garlic in the reduction of hyperlipidaemias. The objective of the present study was to investigate the influence of the aqueous extract of garlic (Allium sativum) to treat the serum cholesterol of rabbits with experimental hypercholesterolemia. The animals were divided into G1 (control group) and G2 (group treated with garlic). The experiment was developed according to 3 phases: during the 1st phase, all animals were provided with a regular diet to evaluate the basal cholesterol; during the 2nd phase, all animals received a supplemented diet until the end of the experiment, in order to develop hypercholesterolemia and, in the 3rd phase, the animals on G2 received the garlic treatment. The cholesterol registered on the 1st phase was 39.94 ± 9.57 mg dL-1. On the 2nd phase, there was an increase on the serum cholesterol level in both groups - higher than 100 mg dL-1. Concerning the treatment, the garlic did not reduce the serum cholesterol in rabbits.

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The effects on soil chemical properties brought about by cover crops vary considerably. This study was conducted to evaluate nutrient uptake by five cover crops used for grain, seed and forage production at different seed densities per hectare, as well as uptake by spontaneous vegetation, and their effect on the chemical properties of two Oxisols when grown in rotation with soybean and corn. The experiments were set up in Votuporanga, SP, Brazil and Selvíria, MS, Brazil in March 2008 after conventional soil tillage. A randomized complete block experimental design was used with four replications with the following cover crops at different seed densities: Sorghum bicolor at 6, 7 and 8 kg ha-1; Pennisetum americanum at 10, 15 and 20 kg ha-1; Sorghum sudanense at 12, 15 and 18 kg ha-1; hybrid of Sorghum bicolor with Sorghum sudanense at 8, 9 and 10 kg ha-1; and Urochloa ruziziensis at 8, 12 and 16 kg ha-1. We also used a spontaneous vegetation control. After management of the cover crops, in the first year of study, soybean was sown in no-tillage system and, in the second year, corn was sown, also in a no-tillage system. We evaluated the dry matter yield of different cover crops, nutrient uptake by the cover crops, and the chemical changes in the soil. It was found that in clayey soils with high aluminum content, as in Selvíria, sudan grass at a seed density of 18 kg ha-1, and sorghum at a seed density of 6 kg ha-1, in combination with liming, contributed to reduction of aluminum content and high potential acidity and an increase in base saturation. The different seed densities of each cover crop did not affect the dry matter yield of the cover crop itself, but affected nitrogen uptake of the hybrid Sorghum bicolor with Sorghum sudanense at a seed density of 10 kg ha-1, with lower uptake than at a seed density of 8 kg ha-1. Seed density also affected the organic matter content in the soil with sudan grass, with the seed density of 15 kg ha-1 providing more organic matter content than a seed density of 18 kg ha-1.

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When registering spectral radiance from surface targets, digital numbers recorded by the imagery sensor may vary. Such variation causes imperfections on the images coming from aerial surveys. Variation in the image brightness related to the distance from the center of the image is known as the vignetting effect. Correcting this effect aims at achieving an homogeneous image brightness. The purpose of this paper is to present a specific methodology to determine a model in order to minimize this vignette effect based on a model fit by Least Squares Method (LSM), using digital numbers (DN) from shadowed regions. The main hypothesis is that the recorded DN of shadow pixels should be suitable to model the vignetting effect. Considering that the vignetting effect could be modeled as a trend of spatial image variation, a trend surface analysis of a sample of pixels from shadowed regions was carried out. Two approaches were adopted to represent the shadow regions of an image. The first one takes into account the components R, G, B of the aerial image within the visible spectral band, and the second one considers the component I of the HSI image. In order to evaluate the methodology, a study case with a color aerial image was carried out. The findings showed that the best results were obtained by applying the model in the RGB components, which allows to conclude that the vignetting effect can be modeled based on trend surfaces fit on shadow regions DN.

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Q field experiment was carried out at the Gralha Azul Experimental Farm/PUCPR, in the municipality of Fazenda Rio Grande-PR, to evaluate the effect of different times and coexistence extension periods of weeds interfering in corn yield. The experiment was arranged in a complete randomized complete block design and the treatments in a 4x5+2 factorial, with four replications. The treatments were as follows: four initial weed control periods (0-0, 0-7, 0-14 and 0-21 DAE) and five restarted weed control periods until the harvest (28, 42, 56, 70 and 84 DAE) and two checks, weedy and weed-free. The experiment was carried out under a no-till system. The period prior to weed interference (PBWI), the start of the critical period of weed interference (CPWI) and the infesting community were evaluated. When the initial weed control period was 0-0 day, the PPWI was at 9 DAE of corn; however, with increasing initial weed control periods (0-7, 0-14 and 0-21 DAE) the period prior to weed interference inncreased in relation to 0-0 day of the initial weed control, evidencing the existence of PPWI-S of 17, 24 and 28 DAE of corn, respectively. Thus CPWI initiates at the end of PPWI-S, the period when weed control is indispensable to prevent a significant reduction in corn yield. Coexistance with the weeds throughout the crop cycle reduced yield in 15%, compared to the weed-free check. Nine species of seven botanical families were assessed in the infesting community. Reduced density and dry mass were verified in the weeds that coexisted with corn, compared to those that grew without it, thus evidencing a suppressive effect of corn over the infesting plants.

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Pós-graduação em Agronomia (Produção Vegetal) - FCAV

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Pós-graduação em Biofísica Molecular - IBILCE

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Pós-graduação em Agronomia (Agricultura) - FCA

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Pós-graduação em Agronomia (Agricultura) - FCA