Carrier water quality is one of the main characteristics for an efficient and safe spraying of pesticides. Overall related to the levels of pH and hardness. The objective was to evaluate the ...interaction between water pH and storage time of the spray, containing 2,4-D amine, 2,4-D choline and dicamba, on the visible efficacy in Ipomoea triloba, Bidens pilosa, Amaranthus viridis; and water hardness on I. triloba. Three studies were carried out in a greenhouse. Study 1 with a 3x5 factorial, which factor A being pH of 2, 6 and 10 and factor B being 0, 2, 6, 24 and 36 hours of application after the mixture. Study 2 was a 3x5 factorial for each herbicide, whith factor A being the levels of pH (2, 6 and 10) and factor B being 0, 6, 12, 24 and 48 hours of application after the mixture. The study 3 is a 3x7 factorial, with factor A being the herbicides and factor B levels of water hardness: 0, 65, 125, 250, 500, 750 and 1000 parts per million. The pH of all solutions remained stable for 48 hours after preparation. However, did not interfere in efficacy of dicamba in I. triloba. Also, longer time between preparing the spray with 2,4-D formulations and application caused reduction efficacy on I. triloba. Also, the level of water hardness decreased control on I. triloba. The pH of carrier water did not affect efficacy of 2,4-D and dicamba on the weeds; however, longer time of the spray application reduce the visible efficacy.
RESUMO: A qualidade da água é uma das principais características para uma aplicação eficiente e segura de pesticidas. De maneira geral, a qualidade da água está relacionada aos níveis de pH e dureza. Assim, o objetivo foi avaliar a interação entre o pH da água e tempo de mistura da calda contendo os herbicidas 2,4-D amina, 2,4-D colina e dicamba, na eficácia visível em Ipomoea triloba, Bidens pilosa, Amaranthus viridis; além dos níveis de dureza da água em I. triloba. Três estudos feitos em estufa. Estudo 1 em fatorial 3x5 sendo o fator A pH de 2, 6 e 10 e o fator B 0, 2, 6, 24 e 26 horas da mistura até a aplicação. Estudo 2 em fatorial 3x5 para cada herbicida, sendo o fator A pH de 2, 6 e 10 e o fator B 0, 6, 12, 24 e 48 horas da mistura até a aplicação. Estudo 3 em fatorial 3x7 sendo o fator A os herbicidas e o fator B níveis de dureza da água: 0, 65, 125, 250, 500, 750 e 1000 partes por milhão. O pH manteve-se estável nas 48 horas. Entretanto, não interferiu na eficácia de dicamba em I. triloba. Além disso, maior tempo entre o preparo da calda com as formulações de 2,4-D e a aplicação causou redução da eficácia em I. triloba. Ainda, a dureza da água diminuiu o controle sobre I. triloba. O pH não afetou 2,4-D e dicamba sobre as plantas, entretanto, maior tempo de aplicação reduz a eficácia.
Ryegrass ( Lolium multiflorum Lam.) is an important forage and suffers negative interference from weeds, like annual bluegrass ( Poa annua L.). The competition of annual bluegrass with ryegrass can ...interfere with crop growth and reduce the amount of forage for animal feed. We aimed to evaluate the interference of annual bluegrass in ryegrass crops through the differentiation of niche and establishment. Two experiments were carried out testing different competition strata (shoot, root, and both) and ryegrass establishment with or after annual bluegrass, with increasing populations of annual bluegrass (0, 35, 139, 279, 419 plants m –2). The variables were plant height, height length of the root system, stem diameter, and fresh weight of shoot and root systems of ryegrass. The negative interference of growing populations of annual bluegrass occurred when in competition for the shoot and root systems of ryegrass. The fresh weight of shoots and roots were impacted when competing for the same strata. Ryegrass, established after the population of annual bluegrass, showed less competitive capacity. The negative interference of annual bluegrass in ryegrass is greater when the plants fully compete for the resources of the environment, and when the ryegrass establishes after the competitor.
The action of these herbicides results from the inability of the plant to metabolize them immediately, because they are able to acidify the cell wall of vegetables by the greater activity of the ...proton pump of ATPase, linked to the cell membrane (Senseman, 2007). ...the pH reduction in the apoplast region induced throughout the cell because of the greater activity of enzymes responsible for the loosening of cells (Usepa, 2013). The main effect is drift after application, with phytotoxic effects on susceptible plants (Mortensen et al., 2012), such as tree species in native forest remnants and recovery plantations of degraded areas marginal to areas grown using agrochemical to control pests. In some studies, we found that the injury effect of Dicamba seen to be greater than 2,4-D in some crops (Egan et al., 2014a; MohseniMoghadam & Doohan, 2015). ...the objective of this work is to evaluate the phytotoxicity and photosynthetic alterations in Brazilian peppertree seedlings by applying different doses of 2,4-D and Dicamba simulating drifts. On that occasion, the following were determined net assimilation rate of CO2 (A - pmol CO2 m-2 s-1), stomatal conductance of water vapors (Gs - mol H2O m-2s-1), intercellular CO2 concentration (imol CO2 air mol-1), transpiration rate (E - mol H2O m- 2 s-1), water use efficiency (WUE - mol CO2 mol H2O-1), obtained by the relation between the amount of CO2 fixed by photosynthesis (A) and the amount of transpired water (E), and Rubisco carboxylation efficiency (A/Ci), obtained by the relation between the amount of CO2 fixed by photosynthesis and the internal concentration of CO2.
A utilização de herbicidas pré-emergentes oferece alternativa promissora para o manejo depopulações de plantas daninhas de difícil controle na cultura da soja, como aquelasapresentando tolerância ao ...herbicida glifosato como a poaia-branca (Richardia brasiliensis).Neste trabalho, objetivamos analisar avaliar possíveis diferenças na eficiência de controle eseletividade à soja quando pré-emergentes são aplicados anteriormente, ou logo após asemeadura da cultura. Para tal, conduziu-se experimento de campo empregando 10herbicidas pré-emergentes (além de testemunhas sem controle e capinadas), com 4repetições e aplicando-se os tratamentos antes ou após a semeadura da soja. Resultadosindicam que o momento de aplicação de herbicidas pré-emergentes em relação à semeadurada soja alterou significativamente a eficiência de controle de alguns ingredientes ativossobre plantas daninhas, porém não afetou a seletividade destes. Contudo, os herbicidasdiclosulam, mesotrione, flumioxazina, e a mistura flumioxazina + imazethapyr foramigualmente eficientes para o controle de poaia-branca e caruru, independentemente domomento de aplicação. Os únicos tratamentos com herbicidas que propiciaram controlesatisfatório (>70%) de todas as espécies avaliadas (poaia-branca, caruru e aveia-preta,Avena strigosa Schreb.) foram flumioxazina, e a mistura flumioxazin + imazethapyr.Aplicações em plante-e-aplique resultaram em ganhos produtivos médios de mais de 600 kgha-1 em relação ao aplique-e-plante, possivelmente devido ao controle superior de plantasdaninhas latifoliadas. Em conjunto, estas informações são úteis ao sojicultor, visto que nãoacarretam elevação no custo de manejo, somente afetando o momento de entrada na áreapara aplicação dos pré-emergentes.
Synthetic auxin herbicides constitute major alternatives for managing tough-to-kill weeds such as Ipomoea spp. Adjuvant use is known to positively affect the biological efficacy of pesticides by ...modifying key spraying solution and droplet properties. Determining to what extent the use of adjuvants could change spray solution parameters and affect synthetic auxin herbicides’ efficiency for Ipomoea spp. control were the research goals. The study was conducted in two phases: laboratory and field, respectively. In the laboratory, the pH, the surface tension, and the resources of the herbicide drops were measured. In the field, weed control was evaluated. All adjuvants modified spray solution properties, lowering surface tension values. Most adjuvants decreased pH values as well as number and density of droplets due to an increase in droplet size. Regardless of adjuvant usage, Ipomoea spp. control levels rose more rapidly following 2,4-D spraying rather than dicamba, resulting in lower biomass accumulation when the former was used. Dicamba-containing treatments displayed slightly but significantly lower Ipomoea spp. control levels at the end of the evaluation period. Herbicide efficacy for Ipomoea spp. control was not improved upon the addition to the spray solution of any of the tested adjuvants. Adjuvant use altered spraying solution and droplet properties. 2,4-D spraying allowed for lower Ipomoea spp. biomass and greater control levels relative to dicamba, suggesting it might constitute a better option for Ipomoea spp. control. Even though herbicide efficacy was not improved with adjuvants, their use should still be considered given favorable spraying solution alterations, mainly with some alteration in droplet sizes despite the use of similar spray nozzles tips - maintaining weed control efficacy.
The aim of this study was to investigate the (i) behavior of young Tabebuia serratifolia (Yellow Lapacho) plants exposed to flooding condition, (ii) measuring the physiological and biochemical ...parameters in leaf and root, and (iii) to discover if this species can be used in areas where the flooding occurs frequently. A completely randomized block design with two water conditions (control and flooding) was used. The parameters measured were the leaf water potential, stomatal conductance, transpiration rate, nitrate reductase activity, nitrate, free ammonium, glutamine synthetase activity, total soluble amino acids, total soluble proteins, alcohol dehydrogenase activity, and lactate dehydrogenase activity. The data showed significant differences in all parameters. The reductions were observed in water relations and nitrogen compounds. However, increases were determined in alcohol dehydrogenase and lactate dehydrogenase activities after flooding. Regarding with organs evaluated, modifications more intense into root for many parameters such as glutamine synthetase and lactate dehydrogenase enzymes, and leaf was more responsive in nitrate, free ammonium, and alcohol dehydrogenase activity. Therefore, Tabebuia serratifolia plants are sensitive to flooding, and are not suitable for areas prone to flooding.
Background: Atrial fibrillation (AF) is a common complication after coronary artery bypass grafting (CABG). Since its prevention with prophylactic drug therapy has limited success, alternative ...approaches are desirable. This study examined the efficacy of atrial or biatrial pacing, compared with no pacing, on the incidence of AF after isolated CABG.
Methods: From August 2002 to September 2004, 240 patients underwent CABG. After surgery, right and left atrial epicardial pacing wires were implanted for 72 hours of temporary pacing. Patients were randomly assigned to one of three groups: no pacing (control group), right atrial (RA), and biatrial (BiA) pacing. Cardiac rhythm was monitored continuously during intensive care, or daily on the ward. The primary endpoints of this study were an episode of AF occurring up to 72 hours after CABG and the risk factors correlated with this event.
Results: Atrial and BiA pacing significantly lowered the incidence (1.25% vs 25%, P=0.001) of AF episodes, and were both correlated (odd ratio 0.038; 95% confidence interval 0.005–0.29) with a decrease in rates of postoperative AF. Multivariable analysis identified older age (odd ratio 1.074; 95% confidence interval 1.024–1.12) and no pacing as independent risk factors of postoperative AF.
Conclusions: Temporary right atrial or biatrial pacing after CABG significantly decreased the postoperative incidence of AF. Multivariable analysis identified older age and no pacing as predictors of AF occurrence.
OBJETIVO: Avaliar os efeitos da estimulação atrial direita temporária na prevenção da fibrilação atrial no pósoperatório de revascularização do miocárdio com circulação extracorpórea e identificar os ...fatores de risco para o aparecimento dessa arritmia. MÉTODO: Estudamos 160 pacientes que, ao término da cirurgia de revascularização miocárdica, submeteram-se ao implante de eletrodos epicárdicos na parede lateral do átrio direito e foram randomizados em grupos não-estimulado (NE) e grupo com estímulo atrial direito (AD). O ritmo cardíaco foi monitorizado durante as 72 horas seguintes ao término da operação e as variáveis estudadas foram: a incidência de fibrilação atrial, os fatores de risco pré, intra e pós-operatórios para o seu aparecimento e eventos pósoperatórios. Resultados: Foram detectados 21 (13,1%) episódios de fibrilação atrial, sendo 20 no grupo NE e um no grupo submetido à estimulação do átrio direito (AD). O risco relativo para o desenvolvimento de fibrilação atrial foi de 0,18 (IC 95%= 0,05-0,60) para o grupo AD quando comparado ao grupo NE. A regressão logística identificou que as variáveis idade mais jovem, uso de beta-bloqueador no pré-operatório e presença da estimulação atrial direita estiveram associadas a uma menor razão de chances (odds ratio) para o surgimento de fibrilação atrial no pós-operatório. CONCLUSÕES: A estimulação atrial direita temporária reduziu a incidência de fibrilação atrial pós-operatória. A idade avançada e a não estimulação atrial foram fatores preditivos independentes para a ocorrência dessa arritmia.
OBJETIVO: Avaliar os efeitos da estimulação atrial direita temporária na prevenção da fibrilação atrial no pósoperatório de revascularização do miocárdio com circulação extracorpórea e identificar os ...fatores de risco para o aparecimento dessa arritmia. MÉTODO: Estudamos 160 pacientes que, ao término da cirurgia de revascularização miocárdica, submeteram-se ao implante de eletrodos epicárdicos na parede lateral do átrio direito e foram randomizados em grupos não-estimulado (NE) e grupo com estímulo atrial direito (AD). O ritmo cardíaco foi monitorizado durante as 72 horas seguintes ao término da operação e as variáveis estudadas foram: a incidência de fibrilação atrial, os fatores de risco pré, intra e pós-operatórios para o seu aparecimento e eventos pósoperatórios. Resultados: Foram detectados 21 (13,1%) episódios de fibrilação atrial, sendo 20 no grupo NE e um no grupo submetido à estimulação do átrio direito (AD). O risco relativo para o desenvolvimento de fibrilação atrial foi de 0,18 (IC 95%= 0,05-0,60) para o grupo AD quando comparado ao grupo NE. A regressão logística identificou que as variáveis idade mais jovem, uso de beta-bloqueador no pré-operatório e presença da estimulação atrial direita estiveram associadas a uma menor razão de chances (odds ratio) para o surgimento de fibrilação atrial no pós-operatório. CONCLUSÕES: A estimulação atrial direita temporária reduziu a incidência de fibrilação atrial pós-operatória. A idade avançada e a não estimulação atrial foram fatores preditivos independentes para a ocorrência dessa arritmia.OBJECTIVE: To evaluated the effects of temporary atrial pacing to prevent the atrial fibrillation after coronary artery bypass graft surgery and the risk factors to the occurrence of this arrhytmia. METHODS: We have studied 160 patients who, at the end of coronary artery bypass graft surgery, were submitted to epicardial electrode implantation in the right atrium lateral wall. They were randomized into two groups: non-pacing (NP) group and right atrial (RA) pacing group. The cardiac rhythm was monitorized over 72 hours following to the end of surgery and the variables studied were as follow: incidence of atrial fibrillation; the risk factors pre-, intra-, and postoperative for its occurrence, and postoperative events. RESULTS: There were 21 (13.1%) episodes of atrial fibrillation, 20 in NP group and one in RA group. The relative risk (RR) for development of atrial fibrillation was 0.18 (95% CI; 0.05-0.60) for the RA group when compared to the NP group. The logistic regression identified that the study variables, such as younger age; use of beta-blockers in the preoperative, and the presence of right atrial pacing had been associated to a lower Odds ratios (ORs) for the occurrence of atrial fibrillation in the postoperative. CONCLUSIONS: The temporary atrial pacing reduced the incidence of atrial fibrillation after the CABG surgery. Older age and a non-atrial pacing were the independent predictive factors of the occurrence of this arrhythmia.
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