Produção de girassol ornamental e rosas em vasos por influência da fertilização silicatada

• Autor(a) principal: Zanão Júnior, Luiz Antônio
• Data de Publicação: 2011
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1613
• topic: Pedogênese; Amazônia; Geoambientes; Relação solo-vegetação; Pedogenesis; Amazônia; Geoenvironment; Soil-vegetation relation; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

The Floriculture is an agricultural activity that is growing in Brazil and has a great economic potential. It is known that the use of Si in the greenhouse cultivation of potted ornamental plants has increased the ornamentals yield and improved the final quality of the products. Furthermore, Si plays an important role helping the plants to overcome many biotic and abiotic stresses. However, the use of this element in the fertilization of ornamental plant production is usually not considered. This happens even with Si being present in small amounts in the substrate or hydroponic nutrient solution used for ornamental plants growth and the positive response observed after its application for the plants. The aim of this study was to evaluate the yield of two rose cultivars and one ornamental sunflower cultivar grown in pots in response to Si-fertilization applied in the drench. It was also evaluated the effect of Si in the quality of the ornamental plants produced and the possible modifications in the foliar anatomy and the occurrence of gas exchange in the sunflower plants. In greenhouse, two experiments were conducted in randomized block design, with four replications. In one, the treatments were generated by a 2x5 factorial, with two rose cultivars (Yellow Terrazza® and Red White Terrazza®) and five doses of Si (0; 0,25; 0,50; 0,75 and 1,00 g kg-1) supplied as potassium metasilicate. In the other, it was evaluated the effect of the Si doses (supplied as potassium metasilicate) on yield, leaf anatomy and occurrence of gas exchange in the „Sunbright‟ ornamental sunflower species. The plant height, the culture cycle, the yield, the flower diameter and the longevity of pants were measured. It was determined the concentrations and contents of Si macronutrients and micronutrients in the leaves. Samples from the middle region of the blade in the sixth pair of leaves from xi the top (including midrib) were collected for the anatomical study based on the morphological characteristics. Theepidermis trichomes were analyzed using the clearing and scanning electron microscopy with X-ray microanalysis (SEM-EDS).The thickness of the leaf blade, of the palisade and spongy parenchyma, of the mesophyll, and of the abaxial and adaxial epidermis were measured. The gas exchange parameters, the net photosynthesis, the stomatal conductance and the transpiration rate were measured in the fifth pair of leaves, at the flowering stage, with an infra-red gas analyzer (IRGA). The Analysis of Variance (ANOVA) and regression analysis were performed with the equations adjusted for the variables studied as a function of the Si doses applied. The addition of Si in the drench increased the Si concentration in leaves, increased the yield and improved the quality of potted roses and sunflower, however, the plant response was variable according to the Si dose. The dose of Si necessary to produce 90% of flower dry matter and maximal physical yield was 0.423 g kg-1 for Yellow Terrazza® rose, 0.220 g kg-1 for Red White Terrazza® rose and 0.235 g kg-1 for the sunflower plants. The negative effects of Si were observed with doses above 0.86 g kg-1 for the Yellow Terrazza® rose, 0.55 g kg-1 for the Red White Terrazza® rose and 0.66 g kg-1 for the sunflower plants. Although the thickness of the leaf tissues of sunflower had not been altered by the dose of Si applied, as the dose of Si was raised it was observed an expressive diminishing in the transpiration rate, whereas the net photosynthesis and the stomatal conductance were increased. The ornamental sunflower cv. Sunbright accumulates Si in its leaf trichomes.