Cíntia Maria Teixeira Fialho

Avaliação de formulações de glyphosate sobre soja Roundup Ready

This study aimed to evaluate the effects of three glyphosate formulations (Roundup Ready® and R. Transorb® - both with isopropylamine salt and Zapp Qi®, formulated as potassium salt), on transgenic soybean. CD 219RR variety soybean plants displaying the CP4Epsps gene, tolerant to glyphosate, were cultivated. At 25 days after emergence (DAE), when plants showed the second trifolium completely expanded (stadiums V2-V3 ), formulations were applied at 2,000 g ha-1 . Plants intoxication was evaluated 15 days after application as well as the number and dry matter of leaflets, number of radicular nodules and foliar content of N, P, K, S, Ca, Mg, Fe, Cu, Zn, and Mn at flowering and grain yield at the end of the cycle. Soil basal respiration rate, microbial biomass carbon and metabolic quotient were evaluated through soil samples collected during soybean flowering. Isopropylamine salt, present in the Roundup Transorb formulation, was more harmful to the soybean plants, also providing a negative effect on the soil microbiota. Roundup Ready formulation, registered as transgenic soybean, should not be applied on this crop at a higher rate, since it could alter the content of some nutrients, such as N, Ca, Mg, Fe and Cu, besides causing intoxication in the plants.

Nutrient content in arabica coffee cultivars subjected to glyphosate drift.

The effects of glyphosate on the foliar levels of nutrients in three coffee cultivars (Coffea arabica) were evaluated in this work. A factorial (3 x 5) was used in a randomized block design with four replications, with treatments consisting of three coffee varieties: Catucai Amarelo (2 SL), Oeiras (MG-6851) and Topazio (MG-1190) and five glyphosate doses (0, 57.6, 115.2, 230.4 and 460.8 g ha-1). At 45 and 120 DAA, leaves (third pair) from plagiotrophic branches were collected from the medium part of the plants. Glyphosate intoxication symptoms were characterized by chlorosis and leaf narrowing for the three coffee varieties. There was a reduction in foliar levels of N, P, K, Cu and Zn at 45 DAA, and N, K, Mn and Zn at 120 DAA, in coffee plants treated with glyphosate, regardless of the cultivar used. Cultivar Topazio showed the greatest reductions in the foliar levels of Fe and Mn, at 45 DAA and P and Fe, at 120 DAA, when treated with glyphosate.

Interferência de plantas daninhas sobre o crescimento inicial de Coffea arabica

The goal of this work was to evaluate the effects of weeds on the growth of young Arabica coffee plants, at different densities of infestation. Seedlings of Mundo Novo coffee cultivar were transplanted at the stage of four to five pairs of completely expanded leaves, to pots with capacity of 25 dm3. The experiment was arranged in a randomized block in factorial design (4 x 4), with four weed species (Digitaria horizontalis, Brachiaria decumbens, Brachiaria plantaginea and Mucuna aterrima) at four planting densities coexisting with coffee (zero, two, four, and six plants per pot), with four replications. The weed species were planted 60 days after the coffee plant transplanting (0 DAT). On this date, and on the day the experiment was concluded, at 90 DAT, height, leaf area and stem diameter of the coffee plants were determined. At 90 DAT, measurements were also performed to determine the increase in height, leaf area and stem diameter of the coffee plants, as well as shoot and root dry matter of the coffee plants and weeds and coffee plant root density. Based onthese data, estimations were made for leaf mass ratio, stem mass ratio, root mass ratio, leaf area ratio and root system/shoot ratio of the coffee plants. The species M. aterrima presented the highest reduction rate for plant height, leaf area, dry matter of stem and leaves and girth diameter of the coffee plants. Among the grasses, B. plantaginea presented the highest reduction rate for plant height, leaf area, girth diameter and root density. A negative relation was observed between weed increase and growth variables, and between root mass ratio and root system/shoot ratio.

Teor foliar de nutrientes em plantas daninhas e de café cultivadas em competição

This work aimed to evaluate nutrient accumulation in young coffee plants and weeds cultivated in competition during 90 days. Mundo Novo coffee seedlings at the stage of four to five pairs of fully-expanded leaves were transplanted into pots with 25 dm-3 of substrate. The experiment was arranged in a randomized block design, in a factorial scheme (4 x 4), with four replications. The treatments were constituted of four weed species: Digitaria horizontalis, Brachiaria decumbens, Brachiaria plantaginea, and Mucuna aterrina, at four infestation densities (zero, two, four, and six plants per pot), in coexistence with one coffee plant, during 90 days. To determine the foliar nutrient content, leaves were collected from the median part of the coffee plants and of the weeds. When in coexistence with the coffee plants, all the weeds provided a lower nutrient content in the leaves of the culture, mainly with increased plant density, except for the N concentration in the leaves of the coffee plants that coexisted with M. aterrina. The nutrient contents in the leaves of the weeds differed according to the species, indicating differentiated capacity of nutrient recycling. The weeds presented higher content of some nutrients, as follows: D. horizontalis in P and Fe; B. plantaginea in P, Mg, Mn, Zn and M. aterrina in N, Ca and Zn, regardless of infestation density.

Photosynthetic characteristics of hybrid and conventional rice plants as a function of plant competition

Objetivou-se com este estudo avaliar caracteristicas relacionadas a capacidade fotossintetica de variedades de arroz hibridas e convencionais, de forma a quantificar seu potencial de competicao. O experimento foi instalado em casa de vegetacao em delineamento experimental de blocos casualizados e esquema fatorial 2 x 6, com quatro repeticoes. O fator A consistiu de variedades de arroz (convencional e hibrida) e o fator B de niveis de competicao. Os tratamentos consistiram em manter uma planta da variedade BRS Pelota (convencional) ou Inov (hibrida) no centro da unidade experimental, sob competicao com 0, 1, 2, 3, 4 ou 5 plantas da variedade BRS Pelota na periferia, de acordo com o tratamento. Cinquenta dias apos a emergencia (DAE), concentracao de CO2 subestomatica (Ci - mmol mol-1), taxa fotossintetica (A - mmol m 2 s1) e CO2 consumido durante a avaliacao (DC - mmol mol-1) foram quantificados, bem como a massa seca da parte aerea das plantas (SDM). Plantas hibridas apresentaram maior capacidade fotossintetica que as convencionais, quando sob competicao com ate tres vezes sua propria densidade. Sob mesma intensidade de competicao, plantas hibridas sao superiores as convencionais. No entanto, deve-se enfatizar que em condicoes de campo a menor habilidade competitiva com plantas daninhas normalmente atribuida as variedades hibridas, provavelmente se deve a sua menor densidade de semeadura, mas se a densidade de plantas daninhas e mantida em niveis adequados plantas hibridas de arroz podem apresentar desempenho similar ou normalmente superior ao de plantas convencionais.

Competition of weeds with coffee plants, in two times of infestation.

The aimed of this work was to evaluate the weed interference installed at 60 and 180 days after coffee seedlings transplanted in pots contend 25 dm3 of substrate. The experiment was arranged in a randomized blocs, with four replications, in factorial design (2 x 4 x 2), with two weed species (Brachiaria decumbens and Brachiaria plantaginea), cultured per 90 days, in four densities (zero, two, four and six plants per pot), together with coffee seedlings of different ages: 60 and 180 days after transplanted. In the moment of the experiment harvest was evaluated the increment in plant height, in leaf area and in girth diameter of the coffee, dry matter of weeds and coffee, and coffee root density. It also estimated the leaf mass ratio, stem mass ratio, root mass ratio, root system/shoot ratio of coffee plants. The weeds provided negative interference in the characteristics evaluated. Verified was smaller increase of height, leaf area and total dry matter of coffee plants with the increase of weed density. The effects of plants interference were bigger when the interference was installed sooner. In this case smaller occurred accumulation of growth variables; however both grasses behaved of similar way not differing for the most variables. When the competition was installed later the coffee plants were more sensible to competition the B. plantaginea in relation to B. decumbens. The increase of weed densities promoted bigger allocation of photoassimilates for the shoot part in detriment to coffee root system.

Deriva simulada do glyphosate em cultivares de café Acaiá e Catucaí

This study aimed to evaluate the effects of simulated glyphosate drift on the growth of two cultivars with distinct growing patterns. The experiment was arranged in a randomized block design, with four repetitions, and the treatments were distributed in a factorial scheme 2x5, with two cultivars in the first factor and the glyphosate subdoses (0, 57.6; 115.2; 230.4 and 460.8 g ha‑1) in the second factor. On the day glyphosate was applied and at 45 and 120 days after application (DAA), height, leaf area, stem diameter, and number of plagiotropic branches and leaves were evaluated; at 10, 45 and 120 DAA, plant intoxication symptoms were visually evaluated and at 120 DAA, dry mass accumulation of the stem, leaves, and roots was evaluated. The intoxication symptoms of the coffee plants caused by glyphosate were characterized by chlorosis and leaf narrowing in the two cultivars studied. However, more severe symptoms were verified in the Acaia cultivars from 10 DAA on, such as necrosis of younger leaves in the median part of the plant. It was concluded that Acaia cultivar is less tolerant to glyphosate than Catucai cultivar, since it showed lower growth when submitted to herbicide treatment, i.e., tolerance can vary between cultivars with distinct growing patterns.

Efeito de herbicidas na atividade microbiana do solo

This work aimed to evaluate the effects of herbicides and doses on the microbial activity and inorganic phosphate solubilization potential of a soil cultivated with sugarcane. The treatments were composed by the herbicides ametryn, trifloxysulfuron-sodium, and ametryn + trifloxysulfuron-sodium at 0, 1, 2, 4, and 8 times the reference doses of 10, 0.112, and 7.315 + 0.185 mg dm3 of the active ingredient, respectively. After herbicide application, soil samples were incubated for 15 days and CO2 evolution (C-CO2) was evaluated every three days. At the end of incubation, microbial biomass carbon (MBC), metabolic quotient (qCO2), phosphate solubilization potential, and relative phosphate solubilization were evaluated for the treatments tested. C-CO2 evolution was affected by the herbicides and increasing application doses. Trifloxysulfuron-sodium caused a reduction in C-CO 2 evolution of 10.3% in comparison to the control. MBC and qCO2 were negatively affected by the herbicides ametryn and trifloxysulfuron-sodium + ametryn. Trifloxysulfuron-sodium reduced MBC when applied at decreasing doses; the reverse was observed for qCO2. Phosphate solubilization potential was reduced with the application of ametryn (47.20%) and trifloxysulfuron-sodium + ametryn (13.55%), while trifloxysulfuron-sodium applied singly stimulated this activity in the soil (25.48%). Similar behavior was observed for relative phosphate solubilization.

Impacto de sulfentrazona, isoxaflutol e oxyfluorfem sobre a microbiota de dois solos florestais

Questions regarding the application of pre-emergence herbicides for control weeds in eucalyptus are noteworthy due to the impact of this practice on the environment, particularly on soil microbial activity and beneficial micro-organisms such as mycorrhizal fungi and phosphate solubilizers. The aim of this research was to study the impact of applying herbicides sulfentrazone isoxaflutole and oxyfluorfen on mycorrhizal colonization, microbial biomass and microbial activity of two forest soils cultivated with eucalyptus. The trial was conducted in a greenhouse using two soils, one clay and sandy loam distributed in 12 dm3 pots. The 4x3 factorial design was used , with three herbicides (sulfentrazone, oxyfluorfen, isoxaflutole) over the untreated control and three assessments (5, 20 and 70 days after application (DAA)), in a completely randomized design with four replications . After herbicide application seedlings of the hybrid Eucalyptus grandis x Eucalyptus urophylla. We evaluated the microbial biomass of the soil respiration rate, the quotient and the metabolic potential of solubilization of inorganic phosphate at 5, 20 and 70 DAA. At 70 DAA verified the percentage of roots colonized by mycorrhizal fungi and spore viability in the soil. The sulfentrazone, isoxaflutole and oxyfluorfen as well as the time of application affected the microbiological indicators differently. In the sandy loam soil sulfentrazone was more harmful to microbial biomass, mycorrhizal colonization and microorganisms solubilizing inorganic phosphate. In clay soil, however, the application of the three herbicides did not affect microbial biomass, but reduced root colonization of eucalyptus by mycorrhizal fungi and the potential solubilization of inorganic phosphate. The sulfentrazone stood for caused an increase in the number of non-viable spores of mycorrhizal fungi in the soil.

GERMINAÇÃO DE SEMENTES EM FUNÇÃO DO TRATAMENTO PRÉ-GERMINATIVO DE Chamaecrista

Chamaecrista Moench pertence a familia Leguminosae, subfamilia Caesalpinioideae. Diante da escassez de informacoes sobre os mecanismos de germinacao das especies, objetivou-se com esse trabalho avaliar a eficiencia de tratamentos pre-germinativos para superacao de dormencia de sementes de Chamaecrista debilis . Considerando-se as caracteristicas aparentes das sementes em relacao a espessura do tegumento e sua dureza, foi efetuado teste de germinacao com 12 tratamentos: testemunha- sementes intactas, escarificacao mecânica com lixa d’agua n. 80, imersao em agua a 100 o C por 5, 10, 15, 30 e 60 segundos e imersao em acido sulfurico concentrado por 5, 10, 15, 30 e 60 segundos . Foram avaliadas as porcentagens de germinacao das sementes e o indice de velocidade de germinacao, alem do teor de agua das sementes de Chamaecrista debilis . Utilizou-se o delineamento inteiramente casualizado com quatro repeticoes, e as medias foram comparadas pelo teste de Scott-Knott, a 5% de probabilidade. As sementes de Chamaecrista debilis apresentaram grau de umidade de 11,71%. Os tratamentos com agua a 100oC por 5, 10 e 15 segundos e acido sulfurico por 15 segundos foram os mais eficientes em promover a germinacao, indicando que a dormencia nessa especie tambem deve-se a impermeabilidade do tegumento.