It was studiedthe effects of shading (0, 36 and 54%) and of four nitrogen doses (0, 50, 100and 150 mg N/dm3 of soil) on the morphogenetic traits and on thetillering of grasses of Brachiaria genus (B. decumbens, B.ruziziensis and B. brizantha cv. Marandu and cv. Xaraes), cultivatedin pots with 5 kg substrate. It was used a complete random design, in a 3 ×4 × 4 factorial scheme with three replications. Nitrogen promoted increasein leaf appearance rate and in average leaf blade length, whereas shading increasedstem elongation rate. Leaf elongation rate and tillering varied with the interactionamong shading percentages and nitrogen doses. Shading increased response efficiencyof leaf elongation rate to nitrogen doses, but reduced for tillering, evidencingpriority existing tillering growth in detriment to appearance of new tillerswhen there is light restriction for the plants. Phenotypic adjustments, in responseto light reduction, indicate that the studied grasses present tolerance to moderateshading.
