Potassium supply to cotton roots as affected by potassium fertilization and liming

Cotton (Gossypium hirsutum) is known to have a high requirement for K and to be very sensitive to low soil pH. Most of K reaches plant roots by diffusion in the soil. As K interacts with Ca and Mg, liming can interfere in K movement in the soil, affecting eventually the plant nutrition. The objective of this work was to study the effect of dolomitic lime and 0, 15, 30, 45 and 60 g kg-1 of K on the supply of K to cotton roots. Cotton plants were grown up to 40 days in 5 L pots containing a Dark Red Latosol (Typic Haplusthox) with 68% and 16% of sand and clay, respectively. There was an increase in dry matter yields and in K accumulation due to K fertilization. Root interception of soil K was also increased by K application, but was not affected by lime. Mass flow and diffusion increased linearly with K levels up to 60 mg kg-1, in pots with lime. In pots without lime the amount of K reaching the roots by diffusion increased up to 45 mg kg-1, but decreased at the highest K level. Accordingly, there was more K reaching the roots through mass flow at the highest K level. This happened because there were more fine roots in pots without lime, at the highest K level. As the roots grew closer, there was a stronger root competition leading to a decrease in the amount of K diffused to cotton roots.

Growth and nutrient concentration in coffee root system under weed species competition

The effects of competition of six weed species on growth, nutrient concentration and nutrient content of coffee plant root system under greenhouse conditions were evaluated. Thirty days after coffee seedling transplantation into 12 L pots with soil level area of 6.5 dm². Weeds were transplanted or sowed in these pots, at densities of 0, 1, 2, 3, 4 and 5 plants per pot. The duration of competition (or weedy periods) from weed transplantation or emergence until plant harvesting, at the weed preflowering stage, were (in days): 77 (Bidens pilosa), 180 (Commelina diffusa), 82 (Leonurus sibiricus), 68 (Nicandra physaloides), 148 (Richardia brasiliensis) and 133 (Sida rhombifolia). Dry matter of coffee plants was linearly reduced with increasing B. pilosa and S. rhombifolia density, with pronounced effect of B. pilosa. C. diffusa was the only weed species whose increasing density in the pots did not diminish crop root dry matter. L. sibiricus, N. physaloides and R. brasiliensis reduced root dry matter of coffee plants by 75, 52 and 47%, respectively, as compared to the weed-free treatment, regardless of weed density. Under competition, even though weed species showed lower macronutrient concentration in the roots (except for P), they accumulated 4.2 (N), 12.3 (P), 4.3 (K), 5.5 (Ca), 7.6 (Mg) and 4.4 (S) times more nutrients in the roots than the coffee plants. Crop and weed nutrient concentration, as well as competition degrees greatly varied depending on both weed species and densities.

Growth and yield of corn grain and green ear in competition with weeds

Studies on plant growth are interesting because they provide explanations for the factors that influence yield in various crops. The objective of this work was to evaluate growth and yield in corn cultivar AG1051, when in competition with weeds. Cultivar AG 1051 was submitted to two groups of treatments: weed control, and sampling periods for dry biomass evaluation. The weed control treatments consisted of hoeing (two hoeings performed at 20 and 40 days after sowing) and no hoeing. Sampling periods consisted of collecting the above-ground part and roots of corn every fifteen days, until 105 days after sowing (DAS); the first sampling was performed 30 DAS. A completely randomized block design with ten replicates was used. For the characteristics evaluated in a single season, statistical analyses were carried out as a random block experiment. For the characteristics evaluated in several periods, statistical analyses were carried out as random blocks with split-plots (weed control assigned to plots). Fourteen weed species, unevenly distributed throughout the experimental area, were the most important. The growth observed for the above-ground part and root system of corn was 30% smaller in the non-hoed plots, compared to the hoed plots. Lack of weed control increased dry matter of the above-ground part of the weeds and reduced the number of unhusked and husked marketable green ears by 23% and 49%, respectively. Grain yield reduction caused by lack of weed control reached 38%.

Green ear yield and grain yield of maize cultivars in competition with weeds

The reduction in herbicide use is one of the greatest interests for modern agriculture and several alternatives are being investigated with this objective, including the adoption of cultivars that suppress weeds. The objective of this study was to verify if maize cultivars develop differently, in competition with weeds, to produce green ears and grain. Randomized complete block design was used, with split-plots and five replications. Cultivars DKB 390, DKB 466, DKB 350, AG 7000, AG 7575 and Master, were evaluated in the plots, without weeding and two weedings (at 22 and 41 days after sowing) in sub plots. Twenty-one species were identified in the experimental area, the most frequent being Gramineae (Poaceae), Euphorbiaceae, Leguminosae (Fabaceae) and Convolvulaceae species. There was no difference in the dry biomass above-ground part of the weeds in the plots of the evaluated cultivars. The cultivars behaved similarly in treatments with or without hoeing, except for plant height and ear height evaluations. Without hoeing, plant height increased in cultivar DKB 390, while plant height and ear height decreased in cultivar AG 7575. In the other cultivars, these traits did not change under weed control. The presence of weeds decreased the values of all traits employed to assess green corn yield, with the exception of the total number of green ears and grain yield.

Corn growth and yield in competition with weeds

Although labor is intensive, evaluating the growth of crops may allow a better understanding of crop performance, including the reasons why certain cultivars can compete better with weeds. This study aims at evaluating growth, green ear yield, and grain yield in corn when in competition with weeds. Cultivars AG 1051 and BRS 106 were grown with (two hoeings, at 20 and 40 days after sowing) or without weed control. In order to evaluate crop growth, six collections of the above-ground part and the root system of corn were performed, every 15 days, with the first collection made 30 days after sowing. A randomized complete block design was adopted, with split-split plots (weed control in plots, cultivars in subplots, and collections in sub-subplots) and ten replicates. Eighteen weed species were found in the experiment area. Increased values of corn leaf area, above-ground part and root system, due to plant age function, were smaller in non-hoed plots than in hoed plots and were dependent upon cultivar. The lack of weed control increased dry matter of weeds aboveground part and decreased green ear yield and grain yield. Cultivar AG 1051 had higher increases in leaf area, above-ground part of the plant and root system, due to plant age function, and controlled weeds better than cultivar BRS 106. In addition, cultivar AG 1051 was superior to other cultivars with respect to most traits used for green corn yield and grain yield assessment.

Root growth of Arabidopsis thaliana (L.) Heynh. treated with humic acids isolated from typical soils of Rio de Janeiro state, Brazil

Humic substances isolated from soil organic matter had been used as stimulators of plant metabolism. Arabidopsis thaliana (L.) Heynh. with only five chromosomes, short cycle and size, is an important model to evaluate the physiological effects of these substances, which are qualitatively and quantitatively influenced by morphogenesis, mineralogy and chemistry of soils. The objective of this study was to evaluate the ambience effects on bioactivity of humic acids. A and B horizons of four typical soils of the North Fluminense were sampled. After isolation and purification, humic acids were applied to plants in increasing concentrations. The number and length of lateral roots and main root length were evaluated and, subsequently, the concentrations of maximum stimulation were determined by dose-response curves and regression equations. The results showed that more stable humic acids isolated from soil in less advanced stages of weathering, high activity clay and high base saturation resulted in better physiological stimulants for Arabidopsis.

Production of cabbage grown in pots containing legumes' root and shoot

Roots effect is not generally considered in studies assessing the performance of crops in response to green manuring. However, such effect can contribute to a better understanding of crop rotation. The aim of this study was to assess the effect of root and shoot of two legumes on the production of cabbage. The experiment was conducted in pots of 10 liters containing substrate of 2:1 soil/sand. The experiment was arranged in a factorial scheme (2x3 + 2) in a randomized block design with five replicates using two legume species (Crotalaria juncea L. and Canavalia ensiformis L), three plant parts (root, shoot, or whole plant), and two additional treatments (mineral fertilization with 100% and 50% of the recommended dose of N for growing cabbage). Pots with legume treatments received mineral fertilizer with 50% of the recommended dose of N for growing cabbage. The experimental plot consisted of a pot containing one plant of cabbage. Legumes were grown in pots and harvested at 78 days. The root biomass was determined in extra pots. Production was assessed using head fresh and dry weight. The application of the whole plant of both legume species reduced cabbage production. However, root or shoot of both legume species was equivalent to 50% of mineral N fertilization required for the cultivation of cabbage.

Comportamento exófilo de Anopheles darlingi Root, em região meridional do Brasil

Observou-se o comportamento da população "Araraquara" de Anopheles darlingi, em seu ambiente original e em relação à sua atividade exófila com isca humana. As coletas foram realizadas às margens do rio Jacaré-Pepira, no Município de Dourado, Estado de São Paulo, Brasil. O ciclo nictemeral caracteriza-se pelo aspecto bimodal, com os dois picos correspondentes a cada crepúsculo, ou seja, vespertino e matutino. O seu detalhamento permitiu detectar bimodalidade secundária, subdividindo cada pico em um eocrepuscular precedendo ao intracrepuscular propriamente dito. A variação sazonal revelou aumento do número de mosquitos na estação chuvosa e quente e nítido declínio na seca e fria. Embora com dados insuficientes, houve indícios de que o An. albitarsis local, apresente também ritmo bimodal em seu ciclo diário de atividade.

Manutenção de colônia de anopheles darlingi root, 1926, em laboratório

Descreve-se a instalação e manutenção inicial de uma colônia de An. darlingi, no município de Araraquara, SP, como parte do programa de pesquisas em malária da Superintendência de Controle de Endemias - SUCEN. Participando-se de experiência semelhante descrita por CORRÊA na década de 70, apresenta as modificações sugeridas por outros autores e pela experiência de seis meses de funcionamento. A perspectiva c dc desenvolvimento de uma colônia com simplificações de técnicas e equipamentos. São dadas informações sobre alimentação de larvas e alados, duração dos estádios larvais, mortalidade e acasalamento.

TOXOCARIASIS: SEROLOGICAL DIAGNOSIS BY INDIRECT ANTIBODY COMPETITION ELISA

Toxocariasis is caused by infection of man by Toxocara canis and Toxocara cati larvae, the common roundworm of dogs and cats. Because larvae are difficult to detect in tissues, diagnosis is mostly based on serology. Non specific reactions are observed mainly due to cross-reactivity with Ascaris sp antigens. This investigation aimed at developing and evaluating an indirect antibody competition ELISA (IACE) employing a specific rabbit IgG anti-Toxocara canis excretory-secretory antigens as the competition antibody, in order to improve indirect ELISA specificity performed for toxocariasis diagnosis. For that, the rabbit IgG was previously absorbed by Ascaris suum adult antigens. Sensitivity and specificity of IACE were first evaluated in 28 serum samples of mice experimentally infected with T. canis embryonated eggs. Adopting cut-off value established in this population before infection, sensitivity and specificity were 100% after 20 days post-inoculation. For human population IACE was evaluated using sera from 440 patients with clinical signs of toxocariasis and the cut-off value was established with 60 serum samples from apparently healthy individuals. Using as reference test the indirect ELISA performed by Adolfo Lutz Institute, sensitivity was 60.2%, specificity was 98% and concordance was 77.3%. Repeatability of IACE was evaluated by the inter-reactions variation coefficient (2.4%).

Ecologia de Anopheles (Nyssorhynchus) darlingi Root em área de implantação de empreendimento hidrelétrico, na divisa dos Estados do Mato Grosso do Sul e São Paulo

INTRODUÇÃO: Hidrelétricas alteram o fluxo das águas e provocam impactos sobre a composição de mosquitos, justificando-se essa pesquisa. O objetivo da pesquisa foi estudar anofelinos de área sob a influência de um novo lago e avaliar a vulnerabilidade relativa à malária. MÉTODOS: Foram feitas coletas de Anopheles nas margens da Represa Porto Primavera, durante as fases do alagamento até sua cota máxima. Utilizaram-se as técnicas: atrativa humana, de armadilha de Shannon e concha entomológica. Os indicadores Riqueza e Diversidade foram utilizados para medir o impacto. A análise das distribuições temporais foi realizada pelo teste Mann-Whitney, considerando localidade, cota e método de captura como variáveis independentes (α=0,05). RESULTADOS: A densidade de Anopheles darlingi oscilou entre as localidades A, B e C, sendo que os maiores picos foram para B e C. Com a estabilidade do lago, no último nível, evidenciou-se a tendência de redução da densidade de Anopheles darlingi. CONCLUSÕES: Sugere-se que o risco de autoctonia de malária nas proximidades do lago permanece inalterado, ficando o alerta para esporádicas infecções humanas.

Effects of flooding of the River Paraná on the temporal activity of Anopheles (Nyssorhynchus) darlingi Root (Diptera: Culicidae), at the border state of Mato Grosso do Sul and São Paulo, Brazil

INTRODUCTION: Study of the temporal activity of malaria vectors during the implantation of a hydroelectric power station on the River Paraná, intended to generate electrical energy. The river separates the States of São Paulo and Mato Grosso do Sul, in Brazil. The objective was to verify whether alterations occurred in the wealth and diversity indices of Anopheles, following two successive floods, extended to the temporal activity and nycthemeral rhythm followed over a five year period. METHODS: Mosquito capture was performed monthly using the Human Attraction Technique and Shannon Traps. The first, executed for 24h, provided the nycthemeral rhythm and the second, lasting 15h, permitted the tracking of Anopheles during the two floods. RESULTS: The bimodal pattern of Anopheles darlingi defined before these floods was modified throughout the environment interventions. The same effect had repercussions on the populations of An albitarsis s.l., An triannulatus and An galvaoi. Activity prior to twilight was less affected by the environment alterations. CONCLUSIONS: The dam construction provoked changes in Anopheles temporal activity patterns, permitting classification of the area as an ecologically steady and unstable situation. Differences observed in Anopheles behavior due to the capture methods revealed the influence of solo and multiple attractiveness inside the populations studied.

Ecological competition and the incidence of Acinetobacter baumannii bloodstream infections in a teaching hospital in Southeastern Brazil

IntroductionRecently, pathogen ecology has been recognized as an important epidemiological determinant of healthcare-associated infections (HAIs). Acinetobacter baumannii is one of the most important agents known to cause HAIs. It is widespread in healthcare settings and exhibits seasonal variations in incidence. Little is known about the impact of competition with other hospital pathogens on the incidence of A. baumannii infection.MethodsWe conducted an ecological study, enrolling patients who presented with healthcare-associated bloodstream infections (HA-BSIs) from 2005 to 2010 at a 450-bed teaching hospital in Brazil. HA-BSIs were said to be present when bacteria or fungi were recovered from blood cultures collected at least three days after admission. Monthly incidence rates were calculated for all HA-BSIs (overall or caused by specific pathogens or groups of pathogens). Multivariate Poisson regression models were used to identify the impacts of the incidence of several pathogens on the incidence of A. baumannii.ResultsThe overall incidence rate of HA-BSI caused by A. baumannii was 2.5 per 10,000 patient-days. In the multivariate analysis, the incidence of HA-BSI caused by A. baumanniiwas negatively associated with the incidence rates of HA-BSI due to Staphylococcus aureus (rate ratio [RR]=0.88; 95% confidence interval [CI]=0.80-0.97), Enterobacter spp. (RR=0.84; 95%CI=0.74-0.94) and a pool of less common gram-negative pathogens.ConclusionsOur results suggest that competition between pathogens influences the etiology of HA-BSIs. It would be beneficial to take these findings into account in infection control policies.

Biologia de Anofelinos Amazônicos. VI. Variabilidade Enzimática em ANOPHELES DARLINGI Root. (DIPTERA, CULICIDAE)

São relatados resultados preliminares sobre o polimorfismo protético de populuções naturais de Anopheles darlingi, procedentes de duas localidades da região amazônica-Ariquemes (Rondônia) e Rodovia PA-422 (Pará). Pata as esterases, foi detectada variação para o locus Est-2na população de Ariquemes, enquanto foi monomórfico na população da PA-422, sendo verificados nesta última, apenas indivíduos com o genótipo Est2*F/Est2*F. A freqüência do alelo Est2*F foi estimada em 0,80 na população de Ariquemes, valor este muito maior do que o observado na população da BR-174 (Manaus/Boa Vista), em estudos anteriores, que foi de 0,48. Os resultados para o sistema da leucina aminopeptidase (LAP) sugerem que a enzima é controlada por três loci, aparentemente monomórficos em ambas as populações.

Fine-root production in two secondary forest sites with distinct ages in Eastern Amazon

The objective of this work was to assess the fine-root (≤ 2 mm diameter) production dynamics of two forest regrowths at different ages. Fine-root production was monitored by the ingrowth core method in one 18-year-old site (2 ha) and one 10-year-old site (0.5 ha), both localized in the Apeú region, Northern Pará State, Brazil. The sites were abandoned after successive shifting cultivation, beginning in 1940. Monthly production of live fine-root was similar between sites and was influenced by rainfall seasonality, with higher production during the dry season than the wet season for mass and length. However, mortality in terms of mass was higher in the 10-year-old site than in the 18-year-old site. The seasonality influenced mortality only in the 18-year old site following the pattern observed for live fine-root. The influence seasonal on mortality in terms of length was different between sites, with higher mortality during the wet season in the 10-year-old site and higher mortality during the dry season in the 18-year-old site. Specific root length was higher during the wet season and at the 10-year-old site. Fine-root production was not influenced by the chronosequence of the sites studied, probably fine-root production may have already stabilized in the sites or it depended more on climate and soil conditions. The production of fine-roots mass and length were indicators that generally showed the same pattern.