985 resultados para Herbivory in leaf-cutting ants


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Pós-graduação em Agronomia - FEIS

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Pós-graduação em Agronomia (Horticultura) - FCA

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Pós-graduação em Agronomia (Ciência do Solo) - FCAV

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Pós-graduação em Agronomia (Genética e Melhoramento de Plantas) - FCAV

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Pós-graduação em Agronomia (Agricultura) - FCA

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Pós-graduação em Engenharia de Produção - FEB

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The quality and efficiency in straw cutting are determinants in the sowing process, according to the occurrence of "tamp" and stops, the magnitude of the straw removal or even the known effects of the seed "envelopment" where the cutting mechanism can not cut the remaining straw. Thus, the objective of this study was to evaluate the performance of different mechanisms for straw cutting of a seeder individualized in different amounts of crop coverage artificially added in a clay soil. The experiment was conducted at Unesp – Sao Paulo State University in the Experimental Farm Lageado, belonging to the College of Agricultural Sciences - Unesp, Botucatu. The experimental design was split plot with four replications, with main plots consisting of five quantities of black oat straw, in area with no-tillage system and subplots of three opening furrows mechanisms, which are: plane disk (PD), corrugated disk (CD) and wavy disk (WD). The wavy disk provided greater rolling resistance, reducing the speed of the set (tractor and equipment). The plane cutting disk showed the highest values of mobilized soil area, deeper penetration into the soil, requiring lower values of vertical force and higher values of lateral force. Regarding the type of waste and doses used, they offered no resistance to cutting and there was no change in the horizontal force on straw.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Engenharia de Produção - FEG

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Pós-graduação em Agronomia (Horticultura) - FCA

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This study analyzed spatial location patterns of Cercocarpus ledifolius Nutt. (curlleaf mountain mahogany) plants, classified as current-year seedling, established seedling, juvenile, and immature individuals, at a central Nevada study site. Most current-year seedlings were located in mahogany stands in which large, mature individuals had the greatest abundance. These stands had greater litter cover and a thicker layer of litter than areas with few current- year seedlings. Most established young Cercocarpus were located in adjacent Artemisia tridentata ssp. vaseyana (mountain big sagebrush) communities, or in infrequent canopy gaps between relatively few large, mature Cercocarpus. We discuss potential roles of plant litter, root growth characteristics, nurse plants, and herbivory in the establishment and renewal of Cercocarpus communities.

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Pós-graduação em Agronomia (Horticultura) - FCA

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The effects of silicon (Si) supplied in the form of potassium silicate (PS) were evaluated on epidemic components of powdery mildew of melon under greenhouse conditions. The PS was applied to the roots or to leaves. In the first experiment, epidemic components were evaluated after inoculation with Podosphaera xanthii. In the second experiment, the disease progress rate was evaluated on plants subjected to natural infection. The area under the disease progress curve was reduced by 65% and 73% in the foliar and root treatments, respectively, compared to control plants, as a consequence of reductions in infection efficiency, colony expansion rate, colony area, conidial production and disease progress rate. However, root application of PS was more effective than foliar application in reducing most of the epidemic components, except for infection efficiency. This can be explained by the high Si concentration in leaf tissues with root application, in contrast to the foliar treatment where Si was only deposited on the external leaf surfaces. The effects of PS reported in this study demonstrated that powdery mildew of melon can be controlled, and that the best results can be achieved when PS is supplied to the roots.

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Biochemical responses inherent to antioxidant systems as well morphological and anatomical properties of photomorphogenic, hormonal and developmental tomato mutants were investigated. Compared to the non-mutant Micro-Tom (MT), we observed that the malondialdehyde (MDA) content was enhanced in the diageotropica (dgt) and lutescent (l) mutants, whilst the highest levels of hydrogen peroxide (H2O2) were observed in high pigment 1 (hp1) and aurea (au) mutants. The analyses of antioxidant enzymes revealed that all mutants exhibited reduced catalase (CAT) activity when compared to MT. Guaiacol peroxidase (GPOX) was enhanced in both sitiens (sit) and notabilis (not) mutants, whereas in not mutant there was an increase in ascorbate peroxidase (APX). Based on PAGE analysis, the activities of glutathione reductase (GR) isoforms III, IV, V and VI were increased in l leaves, while the activity of superoxide dismutase (SOD) isoform III was reduced in leaves of sit, epi, Never ripe (Nr) and green flesh (gf) mutants. Microscopic analyses revealed that hp1 and au showed an increase in leaf intercellular spaces, whereas sit exhibited a decrease. The au and hp1 mutants also exhibited a decreased in the number of leaf trichomes. The characterization of these mutants is essential for their future use in plant development and ecophysiology studies, such as abiotic and biotic stresses on the oxidative metabolism.