Search

O objetivo com o presente estudo foi verificar a influência de diferentes proporções de turfa vermelha e areia na composição do substrato sobre a colonização radicular por fungos micorríozicos arbusculares (FMA) e no desenvolvimento vegetativo de aveia branca. O experimento foi conduzido em casa de vegetação e os tratamentos foram constituídos a partir de combinações de turfa vermelha (T) e areia (A): 100%A; 25%T+75%A; 50%T+50%A; 75%T+25%A; 100%T. Dez sementes de aveia foram semeadas por vaso plástico preto (350ml de volume), contendo 5 gramas de inóculo de Glomus clarum. Quarenta e três dias após a semeadura da aveia, foram realizadas avaliações de desenvolvimento vegetativo e colonização micorrízica do sistema radicular das plantas, através da presença de estruturas, como hifas, arbúsculos e vesículas. Substratos com maior quantidade de turfa induziram maior desenvolvimento da parte aérea e maior qualidade de raízes (QR), em termos de volume de raízes. Entretanto, a presença da turfa acima de 50% no substrato diminuiu a percentagem de colonização micorrízica da aveia. A similaridade verificada entre as curvas de regressões de percentagem de colonização e Água Facilmente Disponível, com mesmo ponto de máximo, sugerem que a quantidade de mesoporos resultante da combinação turfa/areia influencia na resposta dos FMA, a melhor resposta é obtida em mistura com 32,5% de turfa vermelha. The purpose of this study was to investigate the influence of different proportions of red peat and sand in the substrate on root colonization by arbuscular mycorrhizal fungi (AMF) and the consequent growth of white oats. The experiment was conducted in a greenhouse and the treatments consisted of combinations of read peat (T) and sand (A): 100%A; 25%T+75%A; 50%T+50%A; 75%T+25%A; 100%T. Ten oat seeds were sown per container (350ml volume) containing 5 grams of Glomus clarum inoculum. Forty-three days after sowing, vegetative development and mycorrhizae colonization of the plants’ root system were evaluated by recording the presence of structures such as hyphae, arbuscules and vesicles. Substrates with higher amount of red peat led to increased shoot growth and quality of roots. However, the presence of peat above 50% in the substrate decreased the percentage of colonization of oats by AMF. The similarity of the regression curves of percentage of colonization and readily available water, with the same maximum point, suggest that the amount of mesopores influences the AMF response. It is concluded that the best quality of the substrate for the production of inoculum of Glomus clarum in mixtures of red peat and sand is obtained with about 32,5% red peat content in the mixture.

The objective of the present work was to determine the effects of the interaction between feeding rate and area for periphyton in rearing aquaria for Nile tilapia. Twenty 25 L polyethylene outdoor aquaria were used to hold experimental fish. Three tilapia fingerlings (2.56 ± 0.14 g) were stocked in each aquarium for five weeks (12 fish m -2 ). There were two different feeding rates (full and full minus 30%) and two submerged areas for periphyton development (59.4% and 96.5% of the aquarium surface area; n = 5). Final body weight, specific growth rate and yield in the 96.5%-area aquaria of fish submitted to 30% less feed were significantly higher than in the 96.5%-area aquaria submitted to full feeding rates. Fish growth in the restricted-feed aquaria was favored by their better water quality (higher pH and lower total ammonia nitrogen). There were negative effects on final body weight, SGR, yield and feed conversion ratio of fish in full-feed aquaria when the area for periphyton increased from 59.4 to 96.5%. It was concluded that the combination of restricted feeding rates with large substrate areas for periphyton growth results in better water quality for fish culture than the adoption of each management alone.