Características morfológicas e anatômicas de Brachiaria decumbens, em um sistema silvipastoril

Abstract

Silvipastoril systems may constitute a viable alternative for recovering of pasture areas, reverting the degradation process caused by overgrazing and reduction of soil fertility. The objective of this study was to evaluate the effect of two photosynthetic irradiance conditions (full sunlight or induced natural shade) in two seasons of the year (dry season and rainy season) on forage mass produced by a Brachiaria decumbens pasture as well as on some morphological, structural and anatomy traits. The study was carried out in Coronel Pacheco, Minas Gerais State (Embrapa-CNPGL), from september/2003 to january/2005. The pasture was established in a silvipastoril system, within strips (30 m width) alternated with 10 m width strips planted with the tree species of Acacia mangium and Eucaliptus grandis, being submitted to grazing in a rotational system. It was used an entirely randomized block design with a 2x2 factorial arrangement, with six replications. Preliminary results from the two season measurements indicated higher tiller density, leaf area index and leaf mass in full sunlight conditions. The variable: plant height, stem dry mass, leaf area per tiller and forage mass were not significantly influenced by differential conditions of brightness, although there was a tendency for higher values under the tree canopy. Whith regard to leaf anatomy it was verified a greater thickness in the mesophyll of sun leaves. Histochemical tests detected presence of siliceous bodies and suberous cells in the epidermis of both leaves and lignin and lipid droplets in the entire leaf mesophyll.