Variação sazonal da concentração de nutrientes em folhas de bananeiras, no Vale do Ribeira-SP

The Vale do Ribeira, SP, main agricultural activity is the banana crop, which accounts for most of this fruit production in the State of São Paulo. The nutritional balance of the plant is one of the most important factors for the banana plant can complete the cycle and achieve high productivity. Aiming to evaluate the seasonal variation of leaf nutrient concentration in banana plants in Vale do Ribeira-SP, we used the results of 252 chemical analyses of plant tissue, collected from August 2009 to September 2010, in the 18 representative properties for the region, ten cultivated with subgroup Cavendish banana plant and eight of subgroup Prata banana plant. The largest variation between the macronutrient occurred for K and S, and among the micronutrients, especially for Fe and B. In some dates of evaluation, there was a higher leaf concentration of P, K, Ca and Zn, in subgroup Cavendish banana plants, while the subgroup Prata banana plants showed higher leaf concentration, especially of Mn, B and N. Climatic conditions, especially rain, influenced the leaf nutrient content, especially for K, N, S, B and Fe.

Size-related shifts in dietary composition of Centropomus parallelus (Perciformes: Centropomidae) in an estuarine ecosystem of the southeastern coast of Brazil

Size-related and seasonal evaluation of the dietary composition of fat snook (Centropomus parallelus Poey 1860) in the upper sector of an estuary of the southeastern coast of Brazil were carried out based on stomach analyses of specimens ranging from 40 to 170 mm standard length. Results reveal that C. parallelus is a carnivorous species feeding mainly on benthic crustaceans. Relatively high stomach replenishment suggests that this environment is an important feeding ground for fat snook juveniles. Multivariate analyses indicated that predator size effect is significantly more important than seasonal variation in determining dietary composition. Predator length was associated with increased consumption of palaemonid shrimps (Macrobrachium spp.) and grapsid crabs, and decreased foraging on tanaids (Kalliapseudes schubarti), thus showing a preference shift from smaller to larger prey. Predator length was also positively associated with an increase in the stomach repletion index. Additionally, allometric growth of both gape and head were consistently correlated with this ontogenetic dietary transition, suggesting that such changes might be related to an individual's ability to capture and consume larger, more elusive prey. The digestive tube is short and grows isometrically, which is in accordance with the carnivorous habit of this estuarine fish and its maintenance through ontogeny.