Efeito do hexazinone isolado e em mistura na eficiência fotossintética de Panicum maximum

Esta pesquisa teve como objetivo avaliar a velocidade e intensidade de ação do hexazinone isolado e em mistura com outros inibidores do fotossistema II, através da eficiência fotossintética de Panicum maximum em pós-emergência. O ensaio foi constituído de seis tratamentos: hexazinone (250 g ha-1), tebuthiuron (1,0 kg ha-1), hexazinone + tebuthiuron (125 g ha-1 + 0,5 kg ha-1), diuron (2.400 g ha-1), hexazinone + diuron (125 + 1.200 g ha-1), metribuzin (1.440 g ha-1), hexazinone + metribuzin (125 + 720 g ha-1) e uma testemunha. O experimento foi instalado em delineamento inteiramente casualizado, com quatro repetições. Após a aplicação dos tratamentos, as plantas foram transportadas para casa de vegetação sob condições controladas de temperatura e umidade, onde ficaram durante o período experimental, sendo realizadas as seguintes avaliações: taxa de transporte de elétrons e análise visual de intoxicação. A avaliação com o fluorômetro foi realizada nos intervalos de 1, 2, 6, 24, 48, 72, 120 e 168 horas após a aplicação, e as avaliações visuais, aos três e sete dias após a aplicação. Os resultados demonstraram diferença nos tratamentos, enfatizando a aplicação do diuron, que reduziu lentamente o transporte de elétrons comparado com os outros herbicidas e, em mistura com hexazinone, apresentou efeito sinérgico. Verificou-se com o uso do fluorômetro a intoxicação antecipada em plantas de P. maximum após a aplicação de herbicidas inibidores do fotossistema II de forma isolada e em mistura.

Efeitos da irrigação e adubação nitrogenada sobre a massa de forragem de cultivares de Panicum maximum Jacq.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Produção e composição bromatológica da forragem do capim-mombaça (Panicum maximum Jacq.), submetidos a diferentes fontes e doses de corretivo de acidez

The experiment was carried in protected (greenhouse) atmosphere, in University of Engineering, UN-ESP of Ilha Solteira-SP, with the objective of evaluating sources (limestone and calcium silicate slag) and doses (0,0 0,5 1,0 1,5 2,0 times the recommended dose) of corrective in the bromatolouic composition, tillering and production of dry matter of the grass mombaca (Nuncio? maximum Jacq.). The lineation was completely randomized design, with four repetitions. It was evaluated the tiller number, the production of dry matter, the gross protein, neutral detergent fiber (NDF) and acid detergent fiber (ADF). The corrective influenced the tillering in almost all of the countings. The limestone provided larger production of dry matter in the doses of 1,5 and 2,0 times the recommended dose. The bromatologic composition of the forage was not influenced by the corrective and doses.

Recuperação de larvas de Trichostrongylus colubriformis em diferentes estratos de Brachiaria decumbens E Panicum maximum

The purpose of the experiment was to evaluate infective Trichostrongylus colubriformis larvae vertical migration in two forage grass species. Experimental modules formed by eight plots, established with Brachiaria decumbens cv. Australian and Panicum maximum cv. Aruana, were used in the study, totaling four plots for each grass species. Each plot was divided into six 30 x 30 cm subplots. Larval migration was evaluated in the four seasons of the year, in different plant strata (0-7, 7-14, 14-21, 21-28 and above 28 cm). Four feces deposits were made, one in each season of the year, in the middle of 30-cm tall forage. The feces were collected from the forage ten days after each feces deposit in the experimental subplots. Grass height was measured in each of the strata immediately before the collections. The forage of the different strata was cut from an area measuring 10-cm in radius. The feces were collected manually from the subplots. There was a grass species and grass stratum interaction in the deposit made in autumn (P < 0.05). During that season, most of the larvae were recovered from the Brachiaria grass base; meanwhile, at the forage apex, the biggest average was registered in the aruana grass. Infective larvae (U) recovery was similar among the different strata during spring. In springtime, the biggest L3 recovery occurred at the 21-28 cm stratum from both forage species. No L3 was recovered from any of the No L3 was recovered from any of the grass strata during winter and summer. Study results show that migration of T colubriformis larvae was more influenced by weather conditions Than by forage species.

Collenchyma in Panicum maximum (Poaceae): localisation and possible role

This work relates the occurrence and distribution of collenchyma in Panicum maximum Jacq. P. maximum leaves were collected at different phases of development and sampled from both the base of the sheath and from the sheath-leaf blade transition area. For the stems, the study was made by using hand-cut sections of the internodal base. In the leaves, analyses of serial sections showed, at the base and sheath-leaf blade transition area, a sudden change of tissue at vascular bundle. The vascular bundles are surrounded by sclerenchyma, both in the sheath and the leaf blade, as well as by fibrous threads that occur on the adaxial side of the central bundles. However, at the base of the sheath and at the sheath-leaf blade transition area, sclerenchyma was substituted for collenchyma. In the stem, the substitution of sclerenchyma associated with vascular bundles for collenchyma occurs at the base of the internode, in the pulvinus region. The analyses from transmission electron microscopy showed the presence of lamellated cell wall and active protoplast in collenchyma cells.

Can sieve-element plastids in Panicum maximum (Poaceae) leaves act in the blockage of injured sieve-tube elements?

The ultrastructural features and the plastid changes caused by sample preparation were studied in sieve elements of Panicum maximum leaves. Samples of expanded leaves, taken near the ligule region, were fixed and processed by common light and transmission electron microscopy methods. In mature sieve-tube elements, the protoplast is electron-translucent and plastids are the most frequent organelles. Mitochondria and smooth endoplasmic reticulum segments are also visible and occupy a parietal position within the cell. The plastids are globular and show electron-dense proteinaceous inclusions in the stroma. The protein crystals are predominantly cuneate, but thin crystalloids and amorphous and/or filamentous proteins also occur. The presence of intact plastids plus others in different phases of plastid envelope rupture were interpreted as evidence that this rupture is a normal event in response to injury. This plastid envelope rupture is possibly activated by the release of pressure in the sieve-tube element. After plastid membrane vesiculation, the stroma and the protein crystals are dispersed within the sieve-element ground cytoplasm. The vesicles originating from the plastid envelope move to one cell pole, while protein crystalloids move to the opposite pole and agglomerate in the sieve-plate region. Our findings indicate that these protein crystalloids, which deposit in the sieve plate, may act in sieve-plate pores occlusion, preventing the release of phloem sap, similar to the role of P-protein in dicotyledons. (c) 2008 Elsevier GmbH. All rights reserved.

Estimativa do grau de infestação numa pastagem de Panicum maximum Jacq

Um piquete de capim-colonião (Panicum maximum Jacq) submetido a pastoreio contínuo e a roçadas periódicas revelou, seis anos após o plantio, elevado grau de infestação por outras plantas, destacando-se entre elas a grama-batatais (Paspalum notatum Flügge) que apresentou 85% de frequência e 20,9% de biomassa epígea seca relativa. As dicotiledóneas, em conjunto, apresentaram frequência de 95% e biomassa relativa de 38,7% mas a sua contribuição específica foi muito reduzida. O capim-colonião, por sua vez, apesar da frequência de 95%, apresentou apenas 32,2% de biomassa relativa (diminuição de 67,8%). Estas profundas alterações da flora e da vegetação podem ser atribuidas, em grande parte, a dois fatores: a) ação seletiva da roçadeira; b) preferências alimentares e disseminação endozoócora da gramabatatais pelos bovinos.

Níveis críticos de fósforo em Brachiaria decunbens (Stapf) Prain, Brachiaria humidicola (Rendle) Schweickerdt, Digitaria decumbens Stent, Hypharrhenia rufa (Ness) Stapf, Melinis minutiflora Pal de Beauv, Panicum maximum Jacq. e Pennisetum purpureum Schum

Plantas dos capins braquiaria brachiaria decumbens Stapf (Prain) , quicuio da Amazonia, (Brachiaria humidicola (Rendle) Schweickerdt), pangola (Digitaria decumbens Stent), jaraguá (Hyphrrhenia rufa (Ness) Stapf), gordura (Melinis minutiflora Pal de Beauv), colonião (Panicum maximum Jacq) e napier (Pennisetwn purpure um Schum) foram cultivadas em solução nutritiva completa contendo, 0,12; 0,48; 1,94; 7,75 e 31,00 mg de fósforo por litro, com o objetivo de determinar os níveis críticos internos e externos de fosforo, e avaliar a eficiência com que absorvem e utilizam o fósforo. Aos setenta e cinco dias as plantas foram coletadas, separadas em caules, folhas, bainhas e raízes. Após secagem a 80ºC, as amostras foram pesadas e analisadas para fósforo na matéria seca. Curvas representativas do peso da matéria seca e da concentração de fósforo na matéria seca em função dos níveis de fosforo da solução nutritiva foram obtidas a partir de dados calculados de equações de regressão. Verificou-se que: - As espécies diferiram quanto à necessidade externa de fósforo, sendo B. humidicola e H. rufa as menos exigentes. Seguiram-se em ordem crescente B. decumbens, M. minutiflora, P. maximum, P. purpureum e D. decumbens. - Os níveis críticos internos de fósforo variaram entre as espécies, sendo maior em D. decumbens (0,38%) que nas demais. Seguiram-se em ordem decrescente B. decumbens (0,32%), B. humidioola (0,26%), M. minutiflora (0,24%), P. maximum (o,24%) e P. purpureum (0,20%). - A eficiência de absorção e utilização, do fósforo foi maior para B. humidicola. Seguiram-se em ordem decrescente P. purpureum, P. maximum, D. decumbens , B. decumbens e M. minutiflora.

Efeito de concentrações de espalhante adesionante e doses de glyphosate no controle de Brachiaria decumbens e Panicum maximum

Foram avaliadas as interações entre o glyphosate e o espalhante adesionante correspondente ao condensado de alcoolfenóis com óxido de eteno e sulfonados orgânicos quanto à redução de tensão superficial e ao controle de Panicum maximum e Brachiaria decumbens. Os produtos comerciais apresentavam 360 g e.a./l e 466 g i.a./l, respectivamente. O herbicida reduziu o efeito do espalhante sobre a tensão superficial. Na concentração de 0,1% de p.c., o espalhante maximizou o controle das duas espécies pelo glyphosate. P. maximum mostrou-se menos sensível ao glyphosate que B. decumbens, exigindo doses 24,05% superiores.

Sistema radicular do Panicum maximum Jacq. cv. IPR-86 Milênio adubado com nitrogênio e submetido à lotação rotacionada

Avaliou-se o efeito do nitrogênio no sistema radicular da espécie Panicum maximum Jacq. cv. IPR-86 Milênio, sob pastejo. As doses de N utilizadas foram 0; 150; 300 e 450 kg/ha.ano. As densidades de raízes no pré-pastejo foram avaliadas no quinto ano de aplicação de N, em três profundidades (0-10; 10-20 e 20-40 cm), com crescimento aos 7; 14; 21 e 35 dias após o pastejo. O método de pastejo utilizado foi o de lotação rotacionada. Os valores máximos de densidades de comprimento e de massa das raízes no pré e no pós-pastejo foram obtidos nas doses de N de 204; 206; 192 e 197 kg/ha, respectivamente. Nas doses de N de 0, 150 e 300 kg/ha, o crescimento das raízes (em densidade de comprimento) aumentou, em média, até 29 dias após o pastejo, enquanto, na dose 450 kg/ha, o aumento foi linear. Independentemente da dose de N, 60 a 25% do sistema radicular do cultivar IPR-86 Milênio concentrou-se nas camadas de 0-10 e 10-20 cm de profundidade, respectivamente.

Variação na estrutura da vegetação de duas cultivares de Panicum maximum jacq. (colonião e tabiatã) submetidas a diferentes tipos de manejo. Composição em proteína bruta e digestibilidade In vitro da matéria seca

This work was carried out at FCAV-UNESP, Campus of Jaboticabal, Brazil, to study the effects of nitrogen fertilization (0 and 50 kg N/ha/cut), three sucessive periods of growth (December 21st 1987, January 25th 1988 and February 29th 1988)) and three cutting ages (28, 35 and 42 days) on composition in crude protein and in vitro dry matter digestibility of two cultivars of Panicum maximum Jacq. i.e., Coloniao and Tobiata. Plants were harvested in five vertical layers above soil level (0-20, 20-40, 40-60, 60-80 and over 80 cm). The samples were divided in: green leaves, green stems and dry material. Generally, values of in vitro dry matter digestibility and the levels of crude protein of both cultivars were greater in the higher layers of the vegetation, with a decrease, however, for the other layers and more advanced phases of plants development, mainly with no N fertilization.

In situ degradability of hand harvested or extrusa samples of Tanzania grass (Panicum maximum, Jacq.)

In order to compare the in situ degradability of tanzania grass samples obtained as by extrusa or hand plucked, three ruminal fistulated cows were used in a completely randomized block design with split-plot scheme. Five grams of extrusa or hand harvested grasses were placed in nylon bags rumen incubated during 3, 6, 12, 24, 48, 96 and 120 hours. The degradability of DM, CP, NDF and ADF were, in this sequence, 62.59, 80.88, 50.73 and 46.65%, for hand-harvested grass; and 79.53, 90.97, 71.21 and 65.68%, for extrusa. In situ degradability data of hand harvested samples were not reliable.

Degradabilidade in situ do Capim Panicum maximum cv. Tanzânia Incubado Cortado ou na Forma de Extrusa

The aim of this study was to compare the chemical composition, in vitro dry matter disappearance (IVDMD) and ruminal degradation of Panicum maximum, J. cv. Tanzania samples obtained by clipping (square method) or extrusa collection (animal selection). In the in situ trial, three ruminal fistulated dry crossbred cows, with 499 kg LW, were used in a completely randomized block design with split-plot arrangement design. Five grams of clipped (+/- 2 cm) grass or extrusa samples were placed in nylon bags (7 x 14 cm) and rumen incubated during 3, 6, 12, 24, 48, 96 and 120 hours. The IVDMD and the CP, NDF and ADF content were, respectively, 55.8, 7.6, 81.9 e 43.6%, for the clipped grass and .66.5, 12.1, 78.8 e 39.5%, for the extrusa samples. The potential degradability of DM, C P, NDF and ADF were 62.59, 80.88, 50.73 and 46.65%, for clipped grass; and 79.53, 90.97, 71.21 and 65.68%, for extrusa samples. The quality of the selected animal diet (extrusa) was better than the available forage in terms of IVDMD and chemical composition (high protein and low fiber content). In situ degradability trials carried out with clipped samples, and non selected by animal, could not supply reliable results closed to the animal diet.

Voluntary intake of Tanzania grass (Panicum maximum) under rotational grazing by lactating cows

The study was conducted at Nucleo de Pesquisas Zootecnicas Nordeste of the Instituto de Zootecnia, Ribeirao Preto, SP, in a rotational grazing area of Tanzania grass (Panicum maximum), to estimate the dry matter intake by lactanting cows. The estimation of dry matter intake was calculated from the feces production estimated using extrusa Chromium-mordent and the in vitro digestibility of diet. The three treatments were crossbreed cows fed 3 kg.day(-1) of concentrate, crossbred cows without concentrate suplementation and pure Gir cows also without concentrate supplementation. The milk production was 11.98, 6.53 and 5.46 kg per cow per day, the grass intake was 8.26 +/- 5.66, 11.01 +/- 5.37 and 9.55 +/- 2.31 kg of dry matter per day or 2.15%, 2.37% and 2.34% of live weight for the three experimental groups respectively. The milk production was higher (P<0.01) for cows fed with concentrate. No difference was found for dry matter intake.

Efeito da densidade de plantas de Panicum maximum Jacq. sobre o crescimento inicial de Eucalyptus grandis W.Hill ex Maiden

In order to verify the effect of Panicum maximum plant density on the initial growth of Eucalyptus grandis plants, one assay was conducted under semi-controlled conditions of soil fertility and humidity. Dark red Latossol, collected from the arable layer, was used as substrate in 50 liters amianthus cement boxes. One seedling of Eucalyptus was planted in each box. Fifteen days later, seedlings of P. maximum were transplanted on the same box. The treatments consisted of 0, 4, 8, 12, 16 and 20 plants of P. maximum per m 2. The experimental design was the complete randomized design, with six treatments and eight replicates for P. maximum. One hundred and ten and 190 days after transplanting, Eucalyptus plants grown among P. maximum showed an average reduction of 30.80 and 46.55% stem diameter, 25.10 and 22.50 plant high, 40.18 and 31.29% stem dry weight, 61.32 and 54.06% branch dry weight, 53.72 and 51.82% root dry weight, 44.62 and 38.50% leaf dry weight, 22.51 and 23.16 branch number, 20.72 and 19.97% leaf number, and 33.88 and 17.05% leaf area, respectively.