F.A. Ferreira

Photosynthetic efficiency and water use in eucalyptus plants sprayed with glyphosate

Objetivou-se com este trabalho avaliar a eficiencia fotossintetica e o uso da agua por plantas de clones de eucalipto submetidas ao herbicida glyphosate. O experimento foi realizado em esquema fatorial 4 x 5, com quatro clones de eucalipto (57, 386, 1203 e 1213) e quatro doses de glyphosate (43,2; 86,2; 129,6; e 172,8 g ha-1) e uma testemunha sem herbicida, considerada dose zero, com quatro repeticoes. Aos 7, 14, 21 e 28 dias apos aplicacao do herbicida (DAA) foi avaliada a intoxicacao das plantas, e aos 7 e 21 DAA, o fluxo de gases pelos estomatos (U - mmol s-1), a atividade fotossintetica (A - mmol m-2 s-1), a condutância estomatica (Gs - mol m-1 s-1), a transpiracao (E - mol H2O m-2 s-1) e a eficiencia do uso da agua (QUE - mol CO2 mol H2O-1). Aos 50 DAA, as plantas de eucalipto foram coletadas e colocadas em estufa de ventilacao forcada a 70 oC ate atingirem massa constante. Aos 21 DAA, o clone 1203 comportou-se como mais sensivel ao herbicida. Nao houve diferenca entre clones para as variaveis fisiologicas avaliadas. Aos 21 DAA constatou-se que, com o incremento da dose de glyphosate, houve reducao na condutância estomatica, na taxa de fluxo de gases pelos estomatos, na taxa fotossintetica e na eficiencia do uso da agua. Plantas dos clones 1213 e 1203 apresentaram maior acumulo de massa seca. O aumento da dose do glyphosate promoveu menor acumulo de massa seca das plantas de eucalipto. O glyphosate afetou negativamente o crescimento e a eficiencia fotossintetica e de uso da agua dos clones estudados.

Misturas de herbicidas no manejo de plantas daninhas na cultura do feijão

Avaliou-se a eficacia da combinacao dos herbicidas fomesafen, fluazifop-p-butil e bentazon no manejo integrado de plantas daninhas do feijoeiro (plantio direto e convencional), cultivados em areas anteriormente com milho para grao e silagem. Foi avaliado tambem o residuo do fomesafen no solo aos 125 dias apos a aplicacao (DAA). No plantio convencional, Cyperus rotundus foi a especie dominante, enquanto no plantio direto a infestacao dessa especie foi muito baixa. Nenhuma das combinacoes de herbicidas foi eficiente no controle de C. rotundus. Com excecao de fluazifop-p-butil + bentazon (125 + 480 g ha-1), todas as combinacoes foram eficientes no controle das especies daninhas dicotiledoneas. Nao houve efeito dos tratamentos de herbicidas na produtividade do feijoeiro. O fomesafen, aplicado no plantio direto, causou toxicidade no feijao a partir da dose de 100 g ha-1, sobretudo no milho para silagem. No plantio convencional, sintomas mais leves somente foram observados na dose de 200 g ha-1. Houve residuo de fomesafen no solo apenas na area de plantio direto onde nao havia palhada sobre a superficie do solo, ou seja, na area anteriormente cultivada com milho para silagem. E possivel reduzir doses do fomesafen quando misturado ao bentazon sem afetar a produtividade do feijoeiro. Em areas de feijao cultivado apos colheita do milho para silagem e importante o uso de doses pequenas do fomesafen, para evitar toxicidade a culturas sensiveis subsequentes.

Influence of herbicides on the photosynthetic activity of sugarcane genotypes

The objective of this study was to evaluate the effects of herbicides on the photosynthetic activity of sugarcane genotypes, under field conditions. An experiment was arranged in a randomized block design with split-plots and four replications.The following herbicides were allocated in the main plot: ametryn (2.000 g ha-1), trifloxysulfuron-sodium (22.5 g ha-1), mixture of ametryn + trifloxysulfuron-sodium (1,463 + 37 g ha-1) and a hoed treatment without herbicide. In the subplots, six sugarcane genotypes (RB72454, RB835486, RB855113, RB867515, RB947520 and SP80-1816) were allocated. At 70 days after planting and 15 days after herbicide application, evaluations of stomatal gas flow rate (U - μmol s-1), sub-stomatal CO2 concentration (Ci - μmol mol-1) , photosynthetic rate (A - μmol m-2 s-1) and CO2 consumed (ΔC - μmol mol-1) were conducted on the first plant leaf with visible ligule. Ametryn caused significant damage to the physiological characteristics related to sugarcane photosynthetic activity compared to the trifloxysulfuron-sodium. Sugarcane genotypes show differential sensitivity to herbicide treatments, with the most susceptible to ametryn being RB835486 and RB867515, and the most tolerant RB72454, RB855113, RB947520, SP80-1816 and RB867515. Regarding the evaluated characteristics, there was no difference between the genotypes treated with trifloxysulfuron- sodium and the mixture of ametryn + trifloxysulfuron-sodium.

Leaching of sulfentrazone, isoxaflutole and oxyfluorfen in three soil profiles

The aim of this study was to evaluate herbicide leaching in three soil profiles.Doses of 0.50 and 0.75 kg ha-1 sulfentrazone, 0.113 and 0.169 kg ha-1 isoxaflutole, and 0.72 and 1.08 kg ha-1 oxyfluorfen were applied on the surface of 30 cm high PVC columns filled with the three soil following types: one with a sandy loam texture and two clayey ones with low and high organic matter contents. After applying these herbicides, the columns were submitted to two rounds of 40 mm - simulated rain with a 24h interval between them. Herbicide leaching was detected by bioassay method using sorghum (Sorghum bicolor) plants. Both the activity and movement of the herbicide sulfentrazone in the soil profile increased after application of the highest dose. After application of 0.75 kg ha-1 of sulfentrazone, the highest downward movement was observed in the sandy loam soil, down to 27.5 cm, followed by the clayey soils with low and high organic matter contents, down to 25.0 and 17.5 cm, respectively. A high leaching potential was observed of isoxaflutole, which exceeded 22.5 cm in depth for the three soils and both doses studied. However, oxyfluorfen remained adsorbed in surface layers of soil only. When comparing the types of soil, the highest herbicide activity and movement occurred in the sandy loam soil. Isoxaflutole presented greater mobility than sulfentrazone, while oxyfluorfen showed low leaching potential.

Método rápido para detecção de resistência de capim-arroz (Echinochloa spp.) ao quinclorac

Given that resistance of Echinochloa sp. to quinclorac is widely distributed in rice fields in the states of Rio Grande do Sul and Santa Catarina, and that the standard tests are relatively slow in showing resistance, a quick test must be developed to identify seeds from Echinochloa plants resistant to quinclorac. The trials were conducted under greenhouse and germination chamber conditions. In the germination chamber trial, seeds of four Echinochloa biotypes, characterized as resistant or susceptible to quinclorac, were sown at concentrations of 0, 3.75, 18.75, 37.5, 187.5, 375 and 1875 mg L-1 of quinclorac, and the trial was conducted at 25oC for 14 days. Under greenhouse conditions, the same biotypes were sown and treated with rates of 0, 5.5, 187.5, 375, 750, 1500 and 3000 g ha 1 of quinclorac. Under greenhouse conditions, dry mass and plant height were evaluated 25 days after emergence, and under germination chamber conditions, dry mass and plant height were evaluated 14 days after sowing (DAS), with survival being evaluated 7 DAS. The quick test required less time, labor and material, being as efficient as the greenhouse trial. In addition, it could differentiate both resistant biotypes in function of the resistance level. It is suggested that the concentration of 375 mg L-1 of quinclorac be used as the standard for the quick test, since it showed an adequate safety margin in separating seeds from the resistant and susceptible biotypes.

Absorção, translocação e exsudação radicular de glyphosate em clones de eucalipto: clones

To evaluate absorption, translocation and radicular glyphosate exudation in two Eucalyptus sp. clones (2277 and 531), 14C-glyphosate at 1440xa0gxa0ha-1 were distributed on the third and fourth leaf blade, under 0,030 μCi of radioactivity. Evaluations were performed 0, 2, 8, 32 and 72 hours after herbicide application - HAA. After 8 HAA, 14C-glyphosate on the leaf was similar in both clones. However, considering the whote plant, it was higher in 2277, at any evaluation time. After washing the leaves, higher amount of 14C-glyphosate was verified in the water of 531, indicating its smaller herbicide absorption. In the ground tissue and in the roots, 14C-glyphosate was similar in both clones, at any application time though, showing higher concentrations in the roots. Between 0.78 and 1.16% any of the applied herbicide was exuded into the nutritive solution, without showing difference on translocation and radicular exudation in both clones. The different absorption between the clones can be a likely explanation for the the different tolerance among genotypes.

Tolerance of New Sugarcane Genotypes to Herbicides

The effects of the herbicides ametryn, trifloxysulfuron-sodium and the mixture (ametryn + trifloxysulfuron-sodium) on the yield components of ten sugarcane genotypes were evaluated in this study. The experiment was conducted in a Paleudultand and t was arranged in a randomized block design with split plots. The herbicides ametryn (2.000 g ha-1), tryfloxysulfuron-sodium (22,5 g ha-1) were allocated in the plots as well the commercial mixture ametryn + trifloxysulfuron-sodium (1.463 + 37 g ha-1) and control without herbicide application (hoed). The herbicides were applied at as initial post-emergence of the crop. The sugar cane genotypes (RB72454, RB835486, RB855113, RB855156, RB867515, RB925211, RB925345, RB937570, RB947520 and SP801816) were allocated in the subplots. At 14, 45 and 60 days after treatment application (DTA), sugarcane genotype intoxication by the herbicides was evaluated, using grades. At 14 and 45 DTA, plants had their leaf area and dry matter determined. Plant height was measured at 14 and 360 DTA, and stem productivity was determined by harvest time, 430 days after planting. The genotype RB855156 was the most sensitive to the applied products and the genotypes RB925345, RB947520 and SP80-1816, the most tolerant. In all cases of intoxication, a complete recovery of the crop was observed up to 60 DTA. It was concluded that selectivity of sugarcane to the herbicides ametryn, trifloxysulfuron-sodium and ametryn + trifloxysulfuron-sodium is dependent on the cultivated genotype.

Quantification and chemical composition of epicuticular wax of eucalyptus leaves

This work aimed to quantify and evaluate the chemical composition of the epicuticular wax from leaves of six Eucalyptus clones (UFV01, UFV02, UFV03, UFV04, UFV05 and UFV06). The epicuticular wax was extracted and quantified and their constituents analyzed by gas chromatography coupled with a mass spectrometer, with 31 constituents being identified in the six Eucalyptus clones appraised. The analysis of the samples revealed mostly the presence of hydrocarbons. The component found in larger proportion in the clones UFV02 (36.07%), UFV03 (33.00%) and UFV06 (40.98%) was 3β-acetoxy-urs-12-en-28-al, while in the clones UFV01 (17.80%), UFV04 (11.38%) and UFV05 (17.62%) the component found in larger proportion was hexacosane. The clones UFV02 and UFV04 presented the most variety of chemical components (19 components).This work aimed to quantify and evaluate the chemical composition of the epicuticular wax from leaves of six eucalyptus clones (UFV01, UFV02, UFV03, UFV04, UFV05 and UFV06). The epicuticular wax was extracted and quantified and their constituents analyzed by gas chromatography coupled with a mass spectrometer, with 31 constituents being identified in the six eucalyptus clones appraised. The analysis of the samples revealed mostly the presence of hydrocarbons. The component found in larger proportion in the clones UFV02 (36.07%), UFV03 (33.00%) and UFV06 (40.98%) was 3β-acetoxy-urs-12-en-28-al, while in the clones UFV01 (17.80%), UFV04 (11.38%) and UFV05 (17.62%) the component found in larger proportion was hexacosane. The clones UFV02 and UFV04 presented the most variety of chemical components (19 components).

Competitividade de biótipos de capim-arroz resistente e suscetível ao quinclorac

The objective of this research was to evaluate the competitive potential of two Echinochloa sp. biotypes, resistant and susceptible to quinclorac, collected in rice regions in the state of Santa Catarina. The trial was carried out under controlled environment, and the treatments consisted of plant densities of Echinochloa resistant or susceptible to quinclorac. At the center of the experimental unit, three seeds of the biotype were planted and considered as the treatment. Ten seeds of the opposite biotype were planted on the edges. Ten days after emergence, the number of plants was standardized, with only one plant left at the center of the experimental unit, and a variable number of plants on the edges (0, 1, 2, 3, 4 or 5 plants), according to the treatment. The experimental design consisted of completely randomized blocks in a factorial scheme 2 x 6, with four replications. Forty days after emergence, plant height, number of tillers and leaves, leaf area, fresh and dry weight and water content were evaluated. Data were analyzed by the F-test, using the DMRT test for the increasing density effect, and DMS test to compare the biotypes. All analyses were run at 5% significance level. A correlation matrix was built among the evaluated variables. The Echinochloa sp. biotypes studied, resistant and susceptible to quinclorac, are similar in behavior under high competition levels, with the susceptible ones being superior to the resistant ones in some of the variables studied, at low or moderate competition levels.

Tolerância do Tifton 85 ao glyphosate em diferentes épocas de aplicação

Tifton 85 is a type of forage of high nutritive value, recommended for grazing or hay and silage production. It can be considered a weed, mainly in agricultural and forage seed production areas, probably due to its easy propagation and fast development. Thus, this experiment aimed to evaluate Tifton 85 tolerance to increasing levels of glyphosate during two different seasons. The experiment was arranged in a completely randomized block design with four replications in a 2 x 8 factorial arrangement, and pulverization in two seasons (winter and summer) and eight glyphosate levels (0; 270; 540; 1,080; 2,160; 3,240; 4,320; and 5,400 g ha-1). The experiment was carried out in polyethylene pots with 10L capacity. For each season, control of the Tifton 85 plants was performed at 15, 30 and 60 DAA (days after application). Around 90% of Tifton 85 plant control was observed with 2,636.72 g ha-1 of glyphosate in the winter and 3,607.03 g ha-1 of glyphosate in the summer. The results obtained showed that Tifton 85 is highly tolerant to glyphosate and control is more efficient in the winter than in the summer.