Anatomia e flexibilidade do caule de quatro espécies lenhosas para o manejo biotécnico de cursos de água.

Abstract

The use of vegetation is a common tool in Soil Bioengineering; the plants, in this case, must have flexible stems, among other characteristics. The present work aims to investigate the wood anatomy and the stem flexibility of four species: Phyllanthus sellowianus Müll. Arg. (Phyllanthaceae), Sebastiania schottiana (Müll. Arg.) Müll. Arg., Salix humboldtiana Willd. (Salicaceae) and Salix x rubens Schrank (Salicaceae). The material was collected in the municipality of Santa Maria, Rio Grande do Sul Brazil. The anatomical studies used samples from two individuals by species and the microscopic descriptions followed the IAWA Committee. The flexibility studies used fifty stem samples, with different diameters, for each species. The results showed that the modulus of elasticity is not a good parameter to evaluate stem flexibility; in substitution, it was created a new parameter: the angle of flexibility . Phyllanthus sellowianus showed to be the most indicated species to bioengineering works, followed by Sebastiania schottiana, Salix humboldtiana and Salix x rubens. The prune or even the cut of adult trunks of these species give much protection to slope stability due to the production of younger and more flexible stems. The wood anatomy of Sebastiania schottiana and Phyllanthus sellowianus, here described by the first time, also supports the recent segregation of the last species from the Euphorbiaceae. The great similarity within all studied species configures a reophyllous anatomical syndrome : abundant gelatinous fibres, small vessels, thin rays and absent or rare axial parenchyma; from these features, the presence of gelatinous fibres may be considered as the most important to stem flexibility