The genus Styrax L. (Styracaceae) has a wide distribution in Brazil, occurring in diverse ecosystems. To get a better insight into the ecologieal adaptations ofwood strueture, we studied two speeies, S. camporum and S.jerrugineus from the cerrado, and three species, S. latifolium, S. martii and S. leprosus from the Atlantie forest. For each species, the wood of root and stern was analyzed separately and observations inc1uded qualitative as well as quantitative wood characteristics. The results show that there were significant anatomical differences between the forest and cerrado species as well as between the root and stern wood within single species. Quantitatively, the most informative features in the root wood that separated the forest from the cerrado species were diameter, length and number of vessels, length of fibres, and width and frequeney of rays. In the stern wood, length and frequency of vessels, length of fibres, and width and frequency of rays were the most informative features. In contrast to the forest species, which had larger vessel diameters in their stem wood, the cerrado species had larger vessel diameters in their root wood. The ca1culated vulnerability index indicates that all Styrax species have adaptations to mesic conditions. The cerrado species had the smallest index values, which could be related to the seasonally dry condition of this environment.

RESUMO -Neste trabalho quantificaram-se as principais alterações histológicas ocorridas em cultivares de capim-elefante (Pennisetum purpureum Schumach.), em três estádios de desenvolvimento. A degradação dos tecidos foi avaliada após incubação em líquido ruminal de bovinos. As porcentagens de tecidos presentes em colmo, quilha, limbo e bainha foliares foram determinadas. A quilha e o colmo apresentaram maior proporção de tecido lignificado, enquanto o limbo foliar, maior quantidade de tecido epidérmico e tecido vascular não-lignificado. O tecido parenquimático foi encontrado em menor proporção na bainha foliar, principalmente pela presença do aerênquima, a partir da segunda coleta. A proporção de tecido lignificado aumentou com a maturidade do vegetal, sendo mais acentuado em colmos e limbos. Entre as principais alterações, destaca-se a grande área de degradação encontrada na bainha foliar, mesmo com o envelhecimento dos tecidos. Isto foi associado à presença do aerênquima encontrado nos estádios de desenvolvimento mais avançados.Os estômatos favoreceram a penetração dos microorganismos nos tecidos mais internos da folha (mesofilo). O espessamento e a lignificação da parede celular ocorreram com o envelhecimento das plantas, acompanhado de redução na área de degradação dos tecidos.Palavras-chave: anatomia vegetal, degradação de tecidos, forrageira, lignina, parede celular, ruminante Quantitative Anatomy and in vitro Tissue Degradation in Elephant Grass(Pennisetum purpureum Schumach.) Cultivars ABSTRACT -In this research, the main histological changes that occurred in cultivars of elephant-grass (Pennisetum purpureum Schumach.) at three development stages were determined. The tissue degradation was evaluated after incubation in cattle ruminal fluid. The percentage of tissues presented in the stem, keel, leaf limbo and sheath were determined. The keel and the stem presented greater proportion of lignified tissues, while the leaf limbo presented higher amount of epidermal and non-lignified vascular tissues. The parenchymal tissue was found in minor proportion on the leaf sheath, mainly by the presence of aerenchyma, from the second collection. The proportion of lignified tissues increased with the grass maturity, being more accentuated in stems and limbo. Among the main changes, stand out the greater degradation area found for leaf sheath, even with the tissue become older. This was associated with the presence of aerenchyma found in the advanced development stages. The stomata propitiated intrude of the microorganisms in the most internal leaf tissues (mesofilo). The thickness and lignification of the cell walls occurred as the grass become older, getting along with the reduction in the tissue degradation area.Key Words: plant anatomy, tissue degradation, forage, lignin, cell wall, ruminant Rev. bras. zootec., v.28, n.2, p.223-229 IntroduçãoO capim-elefante (Pennisetum purpureum Schumach.) é uma das forrageiras mais utilizadas para alimentação de bovinos em regiões tropicais, tendo sido bastante estudado quanto à...

RESUMO -O controle químico de espécies do gênero Commelina (trapoerabas) é, muitas vezes, insatisfatório, apesar do uso intenso de herbicidas. O presente trabalho teve como objetivo avaliar o controle de quatro espécies daninhas de Commelina com o uso de diferentes herbicida s aplicados em pós-emergência. Foram avaliadas plantas de C. benghalensis, C. villosa, C. diffusa e C. erecta, em estádio com mais de quatro folhas e caules com cerca de 15 a 25 cm de comprimento, submetidas aos tratamentos com carfentrazone-ethyl (30 e 50 g ha -1 ), glyphosate (960 g ha -1 ), carfentrazone-ethyl + glyphosate (30 + 960 g ha -1 ) e sulfentrazone + glyphosate (150 + 960 g ha -1 ), além de uma testemunha sem aplicação. O delineamento experimental foi inteiramente casualizado, com quatro repetições. Verificouse que o controle químico de trapoerabas foi dependente da espécie, sendo C. benghalensis controlada mais eficientemente com os tratamentos testados, enquanto C. erecta apresentou o menor controle. A aplicação de glyphosate em mistura com carfentrazone-ethyl foi mais eficiente no controle das espécies de trapoeraba do que os demais tratamentos empregados. Palavras-chave: Commelina benghalensis, Commelina diffusa, Commelina erecta, Commelina villosa, controlequímico. ABSTRACT -Chemical weed control of Commelina species (wandering-jew) is sometimes unsatisfactory. This work was carried out to observe the effect of herbicides on

The fungus Austropuccinia psidii is a major pathogen of Eucalyptus spp. that damages mainly early-stage leaves. Resistant clones are the most widely used control measure for the rust disease caused by A. psidii. Essential oils produced in the plant-host cells are associated with resistance. However, the chemical characteristics of Eucalyptus leaves at different stages of maturity, associated with resistance or susceptibility to A. psidii, need to be determined. The aims of this study were to characterize the chemical composition of essential oils in Eucalyptus leaves at three developmental stages of clones of three E. urophylla × E. grandis hybrids that exhibit different resistance levels to rust and to identify probable resistance-related compounds from them. The rust severity following inoculation and the quantity and quality of the essential oil extracted by hydrodistillation were determined at the first, third, and fifth leaf stages of the three clones. Identification of the compounds present in the essential oil was determined by gas chromatography coupled with mass spectrometry. No rust was observed on the three leaf stages of the resistant clone or on the fifth leaf stage of the susceptible clones. Limonene was found at high percentages in essential oils from the three leaf stages of the resistant clone and at low percentages in the susceptible clones. In vitro and in vivo tests indicated that low limonene percentages stimulated A. psidii urediniospore germination and were not fungitoxic, whereas high percentages caused complete inhibition of germination and degenerative changes in fungal reproductive structures. The limonene present in Eucalyptus leaves can be considered a chemical compound related to the rust resistance of Eucalyptus spp.

The influence of trichomes on vertical migration and survival of Haemonchus contortus infective larvae (L3) on different forages was investigated. Four different forages showing different distributions of trichomes (Brachiaria brizantha cv. Marandu, Brachiaria brizantha cv. Xaraes, Andropogon gayanus, and Stylosanthes spp.), and one forage species without trichomes (Panicum maximum cv. Tanzania), were used. Forages cut at the post-grazing height were contaminated with faeces containing L3. Samples of different grass strata (0-10, 10-20, >20 cm) and faeces were collected for L3 quantification once per week over four weeks. In all forages studied, the highest L3 recovery occurred seven days after contamination, with the lowest recovery on A. gayanus. In general, larvae were found on all forages' strata. However, most of the larvae were at the lower stratum. There was no influence of trichomes on migration and survival of H. contortus L3 on the forages.