Silica bodies of grasses from the "Cerrados". IV

Abstract

The shapes of silica bodies of ten species of grasses from the "Cerrados" are studied: Andropogon acuminatus Swallen, A. paniculatus Kunth, Axonopus capillaris (Lam.) Chase, Ischaemum rugosum Salisb., Leptocoryphium lanatum (H.B.K.) Nees, Paspalum conjugatum Berg., P. convexum Humb. et Bonpl., P. scalare var. glabriglume Doell, Trachypogon ligularis Nees and Trachypogon mollis Nees. Silica bodies were prepared for microscopic study from fragments of identified herbarium specimes by washing, charring at 200°C in closed porous clay crucibles, boiling of the residue in 5 N aqueous HCl, washing with water to absence of chlorides, ignition of the residue in closed porous clay crucibles for 2 hours at 800°C and mounting of the white residue in slides, with Canada balsam. Accidental artifacts were detected in a blank test and discriminated by their conspicuous birefringence (which is entirely absent in amorphous opaline plant silica). The shapes of silica bodies are described and compared with homologen particles of other 78 species, previously studied in the same flora. Results are discussed in connection with synecological, autoecological, morphological and physiological problems, as well as in connection with applications to selection of forage plants for the areas of savannas in Central Brazil.