ResumoOs perfilhos são as unidades básicas de crescimento das gramíneas forrageiras e o perfilhamento é responsável pela adaptação e reestabelecimento da gramínea após a desfolhação. Portanto, é importante conhecer as modificações morfológicas dos perfilhos em função do ambiente de desfolhação e da adubação, duas importantes estratégias de manejo das pastagens. Assim, objetivou-se com este trabalho caracterizar as respostas morfológicas dos perfilhos do capimmarandu, em resposta à adubação e à frequência de desfolhação, para melhor compreensão da plasticidade fenotípica dessa planta. O trabalho foi realizado em dois anos experimentais, em que foram avaliados distintos intervalos de corte (sete, 14, 28, 56 e 112 dias), utilizando-se o delineamento em blocos casualizados, com quatro repetições. No segundo ano, além dos mesmos intervalos de corte avaliados no primeiro ano, também foram estudadas duas condições de adubação, sendo uma baixa (21,5 kg.ha -1 de P e 75 kg.ha -1 de N) e outra alta (43 kg.ha -1 de P e 300 kg.ha -1 de N). No segundo ano, utilizou-se o esquema fatorial. Em ambos os anos, as respostas para comprimento de colmo, comprimento da lâmina foliar, espaço entre as lâminas foliares e área foliar e peso do perfilho foram crescentes com o intervalo de corte. No segundo ano, a alta dose de adubos proporcionou maior número de perfilhos vegetativos, espaço entre lâminas foliares, área foliar, peso de perfilhos, folhas e colmos mais compridos, em comparação à baixa dose de adubos. No segundo ano, houve maior densidade populacional de perfilho reprodutivo com o maior intervalo de corte. A desfolhação e a adubação nitrogenada e fosfatada causam modificações morfológicas nos perfilhos do capim-marandu, indicando a ampla plasticidade fenotípica desta gramínea. Palavras-chave: fósforo; intervalo de corte; nitrogênio; Urochloa brizantha. AbstractTillers are the basic units of growth in forage grasses and tillering is responsible for the adaptation and reestablishment of grass after defoliation. Therefore, it is important to understand the morphological changes of tillers due to defoliation environment and fertilization, which are two important pasture management strategies. In this study, we aimed to characterize the morfologic

ResumoÉ possível que a maior disponibilidade de nutrientes no solo promova modificação mais acentuada da forma de crescimento da planta forrageira sob alta frequência de desfolhação. Para testar essa hipótese, caracterizaram-se as modificações na forma de crescimento da Brachiaria brizantha cv. Marandu syn. Urochloa brizantha cv. Marandu (capim-marandu) submetida aos intervalos de corte e à adubação, bem como avaliou-se o efeito dessas modificações sobre as forragens removida e remanescente do corte. O trabalho foi realizado em dois períodos experimentais.

Height variations in a sward over the year may be efficient for increasing plant growth, compared with maintenance of the sward at a constant height. Thus, this experiment was conducted from February 2013 to May 2014 to characterise the development of Urochloa brizantha syn. Brachiaria brizantha cv. Marandu (marandu palisadegrass), managed under three defoliation strategies: constant height (30 cm during the entire experimental period), increasing height (15 cm in the winter, 30 cm in the spring, and 45 cm in the summer), and decreasing height (45 cm in the winter, 30 cm in the spring, and 15 cm in the summer). The experimental design was completely randomised, in a split-plot arrangement, with four replicates. Phyllochron was higher in the winter, but leaf and stem elongation rates and the number of live leaves per tiller were lower compared with the spring and summer. In the summer, the swards under increasing height displayed a higher phyllochron than those under decreasing and constant height. When comparing seasons, the highest leaf senescence rate occurred in spring. In the winter, the sward with increasing height had shorter leaves and stems, in contrast to the summer. The sward under decreasing height showed a high stem elongation rate in the spring. Marandu palisadegrass has great flexibility in terms of defoliation management and a typical seasonal development pattern. Modifying the sward height results in a gradual change in the development of marandu palisadegrass and generates residual effects on the subsequent season.

This work was developed to evaluate the effects of the size and the apical and basal portions of the tiller on the morphology of elephant grass (Pennisetum purpureum cv. Napier). Two experiments were performed. In the first one, the characteristics were evaluated of basal tiller with four sizes (80, 120, 160 and 200 cm). A completely randomized design was used, with three replications. In the second experiment, the morphology of the basal and apical portions, from small tillers (100 cm) and large (180 cm) elephant grass were evaluated. The design was completely randomized and the split-plot scheme was used, with three replications. The numbers of living and dead leaves, stem and leaf lengths, leaf blade width, and tiller mass increased linearly with elephant grass size. The basal portion of the elephant grass tiller had a higher mass (56.2 g), higher percentages of leaf dead (2.1%) and live stem (89.5%), and a lower percentage of live leaf blade (23.4%) than the apical portion. With the increase in size, the elephant grass tiller presents a higher percentage of structural tissues and with a higher stage of development, as well as a lower percentage of photosynthetic tissues. The apical portion of the elephant grass tiller has a higher percentage of photosynthetic tissues and a lower percentage of structural tissues and a higher stage of development compared to the basal portion of the tiller.

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