Adaptive leaf anatomical characteristics of Brachiaria ruziziensis em diferentes ambientes

Studies on morphological plasticity are extremely important to plant breeding seeking to optimize genotype interactions with their environments. The present study evaluated 38 genotypes of Brachiaria ruziziensis cultivated during the rainy (October to March) and dry (April to September) seasons and examined variations in their anatomical characteristics. Fully expanded leaves were collected and fixed in [FAA.sub.70] (formaldehyde: acetic acid: ethyl alcohol) for 72h and subsequently stored in 70% alcohol. Median sections of leaf blades were examined and evaluated according to traditional plant anatomical procedures. Genotypes 15, 27, 40, 53, and 90 demonstrated interactions with the environment in five of the anatomical characteristics evaluated; genotypes 1 and 33 presented no plasticity in any of the characteristics examined. Except for the thickness of abaxial (ABT) and adaxial (ADT) epidermal surfaces, the genotypes showed different behaviors for all the other characteristics evaluated: mesophyll thickness (MT), xylem diameter (XD), distance between bundles (DB), number of bundles (NB), number of bulliform cells (NBC), sclerenchyma tissue area (%L), and bulliform cell area (ABC). Keywords: morphological plasticity, plant anatomy, plant breeding, forage. O estudo da plasticidade morfologica e de grande importancia para os programas de melhoramento que desejam obter materiais promissores quando apresentam a interacao genotipo com ambiente. O objetivo deste trabalho foi avaliar 38 genotipos de Brachiaria ruziziensis cultivados na epoca das aguas (outubro a marco) e da seca (abril a setembro) e observar variacoes nas caracteristicas anatomicas nas diferentes estacoes. Folhas completamente expandidas foram coletadas e fixadas em FAA70 por 72h e armazenadas em alcool 70%. Amostras foliares na parte mediana foram avaliadas de acordo com os procedimentos usuais de anatomia vegetal. Os genotipos 15, 27, 40, 53, e o 90 apresentaram interacao com o ambiente em cinco caracteristicas avaliadas. Os genotipos 1 e 33 nao apresentaram plasticidade para nenhuma mensuracao. Exceto para espessura das faces abaxial (EBA) e abaxial (EDA) da epiderme, os genotipos apresentaram comportamento diferente para as demais caracteristicas avaliadas: espessura do mesofilo (EM), diametro do xilema (DX), distancia entre feixes (DF), numero de feixes (NF) e de celulas buliformes (NCB), area do tecido esclerenquimatico (%L) e das celulas buliforme (ACB). Palavras-chave: plasticidade morf