Atividade de invertases e sacarose sintase em plantas de cafeeiro pulverizadas com solução de sacarose

Uma prática cuja eficiência não foi ainda comprovada cientificamente, é a pulverização dos cafeeiros com solução diluída de sacarose, como fonte de carbono para as plantas. Este trabalho visou estudar o efeito da pulverização de açúcar via folha nos teores endógenos de carboidratos e na atividade das enzimas invertases e sacarose sintase em mudas de cafeeiros (Coffea arabica L.) com baixo (baixo) e alto (normal) nível de reservas de carbono. As pulverizações ocorreram nas concentrações de 0,5 e 1% de sacarose utilizando-se água como testemunha. A aplicação de sacarose a 1% aumentou a concentração de açúcares solúveis totais (AST) em plantas depauperadas, como também aumentou as atividades das enzimas invertase ácida da parede, invertase ácida do vacúolo, invertase neutra do citosol e sacarose sintase. Em plantas com níveis normais de carboidratos não foi observada nenhuma alteração nos teores dos AST, como também nas atividades de tais enzimas. Independentemente dos tratamentos aplicados e do estado fisiológico das plantas, não foram observadas diferenças na transpiração e na condutância estomática, mostrando, desta forma, o controle estomático da transpiração. A fotossíntese foi estimulada a 0,5% e 1% em plantas depauperadas, o que não aconteceu com plantas normais. A pulverização de sacarose em mudas de cafeeiros só é eficiente tratando-se de plantas depauperadas na concentração de 1%.One management practice of which the efficiency has not yet been scientifically tested is spraying coffee plants with diluted sucrose solutions as a source of carbon for the plant. This paper evaluates the effect of foliar spraying with sugar on the endogenous level of carbohydrates and on the activities of invertase and sucrose synthase in coffee (Coffea arabica L.) seedlings with reduced (low) and high (normal) levels of carbon reserve. The concentrations used were 0.5 and 1.0% sucrose, and water as a control. The use of sucrose at 1.0% caused an increase in the concentration of total soluble sugars in depauperate plants, as well as increased the activity of the following enzymes: cell wall and vacuole acid invertase, neutral cytosol invertase and sucrose synthase. In plants with high level of carbon reserve, no increments in total soluble sugar levels or in enzymatic activity were observed. Regardless of treatments or plants physiological state, no differences in transpiration or stomatal conductance were observed, demonstrating the stomatal control of transpiration. Photosynthesis was stimulated with the use of 0.5 and 1.0 % sucrose only in depauperate plants. Coffee seedling spraying with sucrose is only efficient for depauperate plants, at the concentration of 1.0%

Influéncia da aplicacao de cálcio e alagamento do solo sobre características anatómicas das folhas de milho (Zea mays L.) ¨Saracura¨ BRS-4154

A cultivar de milho “Saracura” BRS-4154 apresenta-se tolerante às condições de hipoxia decorrentes do encharcamento do solo. Alterações fisiológicas e anatômicas estão envolvidas no processo de adaptação de plantas a ambientes com baixa pressão de oxigênio. Ao mesmo tempo, o cálcio, além de ser um elemento estrutural que participa dos constituintes da parede celular, mostrou-se eficiente no aumento da tolerância de plantas do milho “Saracura” submetidas a estresse gasoso. O objetivo deste trabalho foi avaliar as alterações morfo-anatômicas das folhas da cultivar de milho “Saracura” sob influência da aplicação de cloreto de cálcio e alagamento do solo em plantas em estádio de floração. O experimento foi conduzido em casa de vegetação, cujos tratamentos consistiram na aplicação ou não de cálcio ao solo com irrigação normal ou alagamento. Cortes transversais e paradérmicos foram preparados de acordo com as técnicas usuais de microtécnica vegetal. Foram observadas alterações significativas para o tamanho dos estômatos, ângulo de curvatura de lâmina foliar, diâmetro polar de células buliformes e espessura de nervura mediana, feixe vascular, metaxilema, mesofilo, epiderme das superfícies adaxial e abaxial.Cacao-Theobroma caca

Calcium partially relieves the deleterius effects of hypoxia on a maize cultivar selected for waterlogging tolerance

Low soil oxygen concentrations due to waterlogging or transient flooding severely reduce maize production. However, genotypes with tolerance or even resistance to hypoxia develop morphological and biochemical adaptation mechanisms which may prove to be useful criteria for the selection and breeding of new improved genotypes. The objective of this work was to evaluate the effect of levels and modes of application of calcium sources on biomass yield, the contents of total soluble sugars and reduced sugars and on the activities of invertase isoforms and phosphoenolpyruvate carboxylase, in a maize variety (BRS 4154) derived from the 14th selection cycle for tolerance to transient soil flooding conditions, when cultivated under waterlogging conditions. The study was carried out in a greenhouse, utilizing 20 kg pots, filled with a lowland soil. The effects of two sources of calcium (CaCl2 , 300 kg ha-1 and CaSO4 , 500 and 1.500 kg ha-1) and three modes of application (applied 8 cm below surface, mixed with the whole soil volume and surface application) were tested in soils kept at field capacity and waterlogged after plants reached growth stage V6. Above ground biomass yield, the contents of total soluble sugars and reducing sugars and the activities of the neutral citosol (INC), acid vacuolar (IAV), acid cell wall invertases and phosphoenolpyruvate carboxylase were determined at the onset of flowering. Calcium application partially relieved the deleterious effect of waterlogging on biomass yield and the activities of INC, IAPC and PEPcase.Maíz-Zea may

PROTEIN WITH INCREASING LEVELS OF UREA IN THE DIET OF DAIRY COWS AT PASTURE

This study aimed to evaluate the effect of replacing dietary crude protein with increasing levels of urea on the digestive, productive and economic parameters of crossbred mid- lactation dairy cows under grazing conditions (Urochloa brizantha cv. Xaraés). Five crossbred cows (Holstein x Zebu) were distributed in a Latin square design (5 x 5) at five experimental periods of 21 days each. Replacement levels of dietary crude protein by urea were 0%, 7%, 14%, 21% and 28%. The intakes of dry matter, crude protein, neutral detergent fiber, and total digestible nutrients, as well as the coefficient of digestibility, were not affected by increasing levels of urea (p>0.05), except for the intake of non-fibrous carbohydrates that increased linearly with supplemental urea levels (p<0.05). Milk yield and   chemical composition, feed efficiency, body weight, and nitrogen use efficiency did not show a significant difference (p>0.05) for cows fed by increasing levels of urea. The financial indicators (gross margin, net margin, profitability, and rate of return) were positive, exceeding operating expenses and the total operating cost. The partial replacement of dietary crude protein by urea in mid-lactation dairy cows under grazing conditions does not interfere with the productive parameters. The results of this study demonstrate that replacing 28% of dietary crude protein by urea could be done in order to reduce feeding costs without negative impact on the performance of lactating cows grazing tropical grass pastures.Este estudo teve como objetivo avaliar o efeito da substituição da proteína bruta da dieta por níveis crescentes de ureia nos parâmetros digestivos, produtivos e econômicos de vacas leiteiras mestiças em lactação, em condições de pastejo (Urochloa brizantha cv. Xaraés). Cinco vacas mestiças Holandês x Zebu foram distribuídas em delineamento quadrado latino 5 x 5, com cinco períodos experimentais de 21 dias cada. Os níveis de reposição de proteína bruta na dieta por ureia foram de 0, 7%, 14%, 21% e 28%. A ingestão de matéria seca, proteína bruta, fibra em detergente neutro e nutrientes digestíveis totais e o coeficiente de digestibilidade, não foram afetados pelo aumento dos níveis de ureia (p>0,05), exceto pela ingestão de carboidratos não fibrosos que aumentaram linearmente com os níveis suplementares de ureia (p<0,05). A produção de leite, a sua composição química, a eficiência alimentar, o peso corporal e a eficiência no uso de nitrogênio não apresentaram diferença significativa (p>0,05) para vacas alimentadas pelo aumento dos níveis de ureia. Os indicadores financeiros (margem bruta, margem líquida, rentabilidade e taxa de retorno) foram positivos, superando as despesas operacionais e o custo operacional total. A substituição parcial da proteína bruta da dieta pela ureia em vacas leiteiras em lactação sob pastejo não interfere nos parâmetros produtivos. Os resultados deste estudo demonstram que a substituição de 28% da proteína bruta da dieta por ureia pode ser feita para reduzir os custos de alimentação sem impacto negativo no desempenho de vacas em lactação mantidas em pastagens de grama tropical

Hydroponic forage of corn and millet grown on different organic substrates

The objective of this study was to evaluate the production and nutritive value of the hydroponic forage of corn and pearl millet grown in different organic substrates. It was carried out in a completely randomized design in 2 x 3 factorial scheme with four replications. The grasses used were corn and pearl millet and sugarcane bagasse, chopped elephant grass and chopped Brachiaria grass as substrates. The harvest was carried out 15 days after sowing, with seed density of 2 kg/m², irrigated with water and commercial nutrient solution. The productive parameters and chemical composition of the hydroponic forage were evaluated. The use of sugarcane bagasse substrate resulted in a greater production of total dry mass for corn among the other treatments, which reflected in better efficiency in the production parameters. As for substrates composed of chopped grass, lower values ​​of neutral detergent fiber were identified in both corn and pearl millet. The substrates and grass species affect the evaluated parameters, in which the use of sugarcane bagasse resulted in greater total production of dry mass using corn. The substrates based on chopped grass reflected in biomass with reduced fiber content, high levels of digestible nutrients, in addition to high protein content

Growth dynamics and senescence of digit grass as a response to several canopy heights

The purpose of this study was to examine the growth and senescence dynamics of Digitaria eriantha cv. Survenola as a response to several canopy heights (25, 35, 45, and 55 cm) of harvests in two seasons of the year (rainy and dry). The experiment was established at the Federal University of Sergipe, in São Cristóvão - SE, Brazil, from 03/26/2015 to 03/28/2016, under a randomized-complete-block design with four replicates. Plots were irrigated, and upon reaching the pre-established canopy heights, they were cut to a 10 cm-residual height. Increasing canopy heights in the dry season led to lower tiller density, for basal and aerial tillers. However, irrespective of tiller type and season, this variable increased after the rest period. Light interception rose with canopy heights (P<0.05) in the dry period and it showed a quadratic response in the rainy season. Greater canopy heights led to a higher (P<0.05) daily leaf senescence rates and daily stem growth rates. Regardless of the season, the total accumulation and net herbage accumulation rates of basal tillers increased as canopy heights did. The greatest canopy height promoted the daily stem production, whereas the lowest height did not allow the grass to express its production potential. The defoliation-height range of 35 to 45 cm is the most recommended, as it favors the control of stem growth and leaf senescence

Práticas de Manejo e os Efeitos na Composição do Dossel Forrageiro

The aim of this review is to address the intensities and frequencies of defoliation and their effects on the accumulation of forage, nutritional value and animal performance. The main limitation in grazing animal production in Brazil is pasture management. With inadequate management it is common to have degraded areas and consequently a reduction in animal productivity. However, the use of the pasture in an adequate way can provide gains to the productive systems. In this context, strategies for the use of pastures were developed in order to enable greater production of forage with greater nutritional value, favoring animal productivity. These management strategies were developed because the research started to involve the entire ecosystem that makes up the pasture, from the soil to the animal product. Thus, it is crucial to know the morphophysiological characteristics of forage plants, as each ecosystem change (climate, animal species, plant structure) will reflect on the development of the canopy. Knowing how each of these factors behaves is essential to achieve greater forage production with sufficient nutritional levels so that there is no loss in animal production or damage to the pasture that makes up the forage system.El objetivo de esta revisión es abordar las intensidades y frecuencias de defoliación y sus efectos sobre la acumulación de forraje, el valor nutricional y el rendimiento animal. El principal obstáculo en la producción de animales en pastos en Brasil es el manejo de los pastos. Con un manejo inadecuado, es común la existencia de áreas degradadas y, consecuentemente, una reducción en la productividad animal. Sin embargo, el aprovechamiento de los pastos de forma adecuada puede posibilitar ganancias a los sistemas productivos. En este contexto, se desarrollaron estrategias de aprovechamiento de pastos con el objetivo de posibilitar una mayor producción de forrajes con mayor valor nutritivo, favoreciendo la productividad animal. Estas estrategias de manejo se desarrollaron porque la investigación comenzó a involucrar a todo el ecosistema que conforma el pasto, desde el suelo hasta el producto animal. Por lo tanto, es crucial conocer las características morfofisiológicas de las plantas forrajeras, ya que cada cambio en el ecosistema (clima, especie animal, estructura de la planta) se reflejará en el desarrollo del dosel. Conocer cómo se comporta cada uno de estos factores es fundamental para que podamos lograr una mayor producción de forraje con niveles nutricionales suficientes para que no haya pérdidas en la producción animal, ni daños en los pastos que componen el sistema forrajero.Objetiva-se com esta revisão abordar as práticas de manejo do vaso forrageiro e seus efeitos sob o acúmulo de forragem, valor nutricional e desempenho animal. A principal limitação da produção de animal a pasto, no Brasil, é o manejo de pastagens. Com o manejo inadequado é a existência de áreas de comumgradas e, consequentemente, uma redução na produtividade animal. No entanto, a utilização da pastagem de modo adequado pode possibilitar ganhos aos sistemas produtivos. Nesse contexto, as estratégias de utilização de pastagens foram elaboradas com o intuito de produção de forma possível com valor nutricional, favorecendo a maior produtividade animal. Essas estratégias de condução são elaboradas pois as pesquisas são feitas para todo o planejamento individual que com o pasto, desde o produto. Assim, é crucial conhecer as características morfofisiológicas de plantasrageiras, pois cada mudança de ecossistema (clima, espécie animal, estrutura da planta) irá refletir no desenvolvimento do dossel. Saber como cada um dos fatores se comporta é essencial para que eles tenham atingido uma maior produção de forragem com níveis nutricionais suficientes para que não haja danos na produção animal, nem os danos à pastagem que compõe o sistema forrageiro

Effect of stocking management and nitrogen supplementation on pasture milk yield

This study aimed to evaluate the effect of the first and last stocking strategies combined with a partial substitution of the protein from the supplement for urea nitrogen on nutrient intake and digestibility, milk composition, and nitrogen balance of primiparous Girolando cows. The cows were allocated to a double 4 × 4 Latin square composed of four animals and four treatments in a 2 × 2 factorial arrangement. Supplements were formulated to provide an intake of 0.6% body weight, with and without the inclusion of 21% urea nitrogen in their composition. The first stocking management method improved nutrient intake and digestibility. Supplementation with urea led to a 47% higher excretion of urine N (g/day) than the urea treatment. The combination of the supplement without urea and the first stocking provided higher intake and retention of nitrogen and higher retained-N levels (%digested N). The combination of a supplement containing 21% urea nitrogen and the first stocking can be used without compromising the nutritional and productive parameters of the cows. Keywords: xaraes grass; tip; repas