The morpho-anatomy of the leaf and stem of B. brizantha and B. humidicola were studied at three plant stratums. The difference among the species and the different stratums were investigated in order to justify the different intensities of consumption that occurs with plant aging. The experiment was carried out in a greenhouse and on plants cultivated in plastic vessels with sterilized sand, receiving nutritive mineral solution. After 70 days, the median leaf of each stratum was collected and divided into limbo and leaf sheath. The same was done to the stem. For the morphological study the total plant height, number of leaves, nodes and sprouts, length and width of blades and sheaths and length and diameter of internodes were measured. For purposes of anatomical characterization the samples were fixed in FAA, embedded in GMA, sectioned in microtome e stained with basic fucsin and Astra blue. The morpho-anatomical studies indicated some parameters that can interfere on tissue digestibility. The species presented different morphology, with shorter and narrower limbo measurements, thereby may affect the accessibility to lower leaves and interfering on the forage consumption. The stem was the fraction with the most variation between species, and showing in B. brizantha a larger stem diameter and thicker culm wall, which make the stem more resistant to apprehension, suggesting a larger number of vascular bundles and, consequently, a high percentage of lignified tissues. Secretory structures were identified below the trichome base cells in the leaf sheaths of B. brizantha, probably as secretory cavities, quite rare in Poaceae and there are no studies about its interference on digestibility and consumption.
anatomy; Brachiaria; grasses; forages; morphology
