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Variation in environmental conditions, such as light availability, can affect herbicide efficacy by altering leaf morphoanatomy. Accordingly, the aim of the present study was to evaluate the influence of light level and herbicide application on leaf anatomy and herbicide efficacy, using Macroptilium atropurpureum as a model weed species. The experiment involved a factorial design (3 × 4), using three light levels (0, 50, or 70% shadow) and four herbicide treatments (no herbicide, glyphosate, carfentrazone-ethyl, or a combination of glyphosate and carfentrazone-ethyl). When combined, the herbicides were efficient in controlling M. atropurpureum under all light levels. However, when applied independently, the herbicides failed to satisfactorily control plants cultivated in full sunlight, and plants cultivated in shaded environments were more sensitive to glyphosate application than those cultivated in full sunlight. The greater efficacy of the herbicides on plants grown under shaded conditions can likely be attributed to changes in leaf morphoanatomy. Plants grown under restricted light conditions exhibit greater average leaf area, lower trichome density, reduced epicuticular wax deposition, thinner leaves, and lower dry mass accumulation, characteristics which are closely correlated to chemical control. The combination of the herbicides presents an additional effect in the control of M. atropurpureum. Also, changes in leaf anatomy caused by light restriction reduce the tolerance of M. atropurpureum to the herbicides.

Objetivou-se com o presente estudo avaliar os danos causados em plantas de eucalipto expostas à deriva de glyphosate em diferentes porções da copa. A simulação de deriva ocorreu por meio da aplicação de 1.080 g ha-1 de glyphosate em cinco porções da copa (0, 25, 50, 75 e 100% dos ramos basais), em quatro áreas de cultivo: áreas I e II, plantas com 0,91 e 2,98 m e altura da copa exposta à deriva de 0,30 e 1,0 m, respectivamente; e nas áreas III e IV ambos os cultivos encontravam-se com 8,15 m de altura, variando a altura de exposição à deriva de 2,0 e 2,5 m, respectivamente. Aos 30 e 480 dias após a aplicação (DAA), foi avaliada a taxa de sobrevivência, e aos 300 e 480 DAA, determinou-se o diâmetro à altura do peito (DAP), altura das plantas, volume de madeira e os seus respectivos incrementos. Já o incremento médio anual (IMA) foi determinado aos 480 DAA. Na área I, em que as plantas se encontravam com 0,91 m de altura, observou-se, no tratamento com 100% dos ramos basais expostos à deriva, redução no estande de plantas na ordem de 18,75 e 38,19% aos 30 e 480 DAA, respectivamente. Nas áreas I e II constataram-se reduções no crescimento de planta em altura e DAP, no volume de madeira e no IMA, à medida que houve aumento da porção da copa exposta à deriva de glyphosate. Todavia, nas áreas III e IV, em que as plantas se encontravam com 8,15 m de altura, não se verificou alterações nas características avaliadas, independentemente da porção da copa exposta à deriva do glyphosate. With the present study we aim to assess the damage caused to Eucalyptus plants exposed to glyphosate drift in different canopy portions. The drift simulation was carried out through application of 1,080 g ha-1 of glyphosate in five canopy portions (0, 25, 50, 75 and 100% of the low branches), in four areas of cultivation. Areas I and II, plants with 0.91 and 2.98 m, and height of canopy drift exposition of 0.30 and 1.0 m, respectively. In areas III and IV both cultivations were 8.15 m high, varying the height of drift exposition between 2.0 and 2.5 m, respectively. At 30 and 480 days after application (DAA), the survival rate was assessed, and at 300 and 480 DAA diameter at breast height (DBH), height, volume and their respective increment were determined. The medium annual increment (MAI) was determined at 480 DAA. Area I, in which the plants were 0.91 m high, we observed that treatment with 100% of the low branches exposed to drift led to stand reduction of the plants around 18.75 and 38.19% at 30 and 480 DAA, respectively. Areas I and II showed reduction in plant growth in height and DBH, wood volume and MAI, to the extent that there was an increase in the portion of canopy exposed to glyphosate drift. However, in areas III and IV, in which 8.15 m height plants were found, no changes were verified for the evaluated characteristics, regardless of the portion of canopy exposed to glyphosate drift.

CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Little is known about the agronomic aspects of Mexican Sunflower (Tithonia diversifolia), in spite of its potential for multiple uses. In this study, we evaluated the effects of application rates of biofertilizer and irrigation on yield, growth, and leaf chlorophyll and nutrient content of Mexican Sunflower. In an experiment in the Brazilian semi-arid region, we used a 5 × 2 factorial arrangement, consisting of five application rates of biofertilizer (0, 40, 80, 120, and 160 m3 ha-1), with and without irrigation. The statistical design was randomized blocks with three replications. Irrigated plants of Mexican Sunflower had greater dry and fresh matter yields, greater height, and greater leaf area index and leaf contents of K, Zn, and B. However, the high concentration of bicarbonate in the irrigation water reduced the leaf contents of N, Ca, S, Fe, and Mn. The mean increase in the two cuttings obtained with the use of irrigation was 350% and 314% for fresh and dry matter, respectively. The increase in the biofertilizer application increased the leaf chlorophyll contents of irrigated plants; however, it did not result in production or nutritional gains. In regions with low availability of rainfall, irrigated cultivation of Mexican Sunflower is recommended.

The use of biofertilizers in agriculture is a promising alternative to mineral fertilizers and as a destination of manure. The objective of this study was to evaluate the morphological characteristics, biomass production and leaf nutrient content of irrigated corn and millet fertilized with swine biofertilizer. Two experiments were conducted between June and September 2011 using corn and millet grown on a Red-Yellow Latosol in a randomized block design consisting of six treatments and four repetitions: swine biofertilizer doses to provide 0, 50, 100, 150 and 200 kg/ha P2O5 and one additional treatment using NPK 4-14-8 mineral fertilizer. Each dose of phosphorus provided by the swine biofertilizer was compared by the Dunnett test to the additional treatment with mineral fertilizer and significance was defined when P

Objetivou-se neste trabalho avaliar a persistência e o risco de intoxicação de espécies de eucalipto para mistura de herbicidas picloram + 2,4-D em aplicação prévia ao plantio florestal. O experimento foi implantado em campo, em delineamento inteiramente casualizado com 6 repetições, no esquema fatorial 4 x 5, com quatro espécies (Eucalyptus urophylla, E. globulus, E. saligna e Corimbia citriodora) e cinco doses de herbicida à base de picloram + 2,4-D (64 + 240gL-1 ): 0, 3, 4, 5 e 6Lha-1 do produto, aplicadas 30 dias antes da implantação da cultura. Aos 15 e 40 dias após o plantio (DAP), foram feitas avaliações fisiológicas. Aos 90 dias após a aplicação do herbicida (DAA), foi realizado um bioensaio para identificar o efeito residual do produto. Nenhuma espécie apresentou sintoma visível de intoxicação, porém ocorreram alterações fisiológicas. Para taxa fotossintética, houve diferentes respostas, com redução para maiores doses, exceto em E. saligna. Aos 15DAP E. saligna e E. urophylla apresentaram taxas superiores para condutância estomática e transpiração. Aos 40 DAP, constatou-se que o aumento das doses ocasionou diminuição linear na condutância estomática. A eficiência no uso da água das plantas foi menor aos 15 DAP nas doses mais elevadas, não havendo alterações aos 40 DAP. Não foram observados sintomas de intoxicação no bioindicador aos 90 DAA. Entretanto, o aumento das doses aplicadas ocasionou efeito linear positivo no acúmulo de biomassa do bioindicador. A mistura de picloram + 2,4-D não causou alterações morfológicas, porém desencadeou respostas fisiológicas negativas nas plantas. The objective was the assessment of the persistence and risk of intoxication of eucalyptus species by mixing picloram 2,4-D herbicide on application prior to forest planting. The experiment was deployed in the field in a completely randomized design with 6 repetitions, in a 4 x 5 factorial scheme, with four species (Eucalyptus urophylla, E.globulus, E.saligna and Corimbia citriodora) and five doses of the picloram base herbicide + 2,4-D (64 + 240 g L-1): 0, 3, 4, 5, and 6 L ha-1 of the product, applied 30 days before deployment of culture. At 15 and 40 days after planting (DAP), physiological assessments were carried out. At 90 days after herbicide application (DAA) a bioassay took place to identify the residual effect of the product. No species showed visible symptoms of intoxication; however, there were physiological changes. For photosynthetic rate there were different responses, with reduction for larger doses, except in E.saligna. At 15 DAP, E.saligna and E.urophylla showed higher rates for stomatal conductance and transpiration. At 40 DAP, it was found that increasing the doses caused a linear decrease in stomatal conductance. Water use efficiency of plants was lower at 15 DAP in higher doses, with no changes at 40 DAP. Toxic symptoms were not noticed the in bioindicator at 90 DAA. However, increasing the applied doses caused a positive linear effect on the accumulation of biomass of the bioindicator. The mixture of picloram + 2,4-D did not cause morphological changes, but triggered negative physiological responses in the plants.