-Plants kept under competition tend to modify their morphology to optimize the use of production factors. This study aimed to evaluate the effects of competition between transgenic maize and five weed species on the growth and yield of transgenic maize hybrid. The experiment used a randomized block design with four replicates in a factorial 5 x 2 + 6 scheme consisting of a combination of maize under competition with five weed species (Bidens pilosa, Commelina benghalensis, Brachiaria brizantha, Sorghum arundinaceum and Ipomoea triloba) in two weed densities (15 or 30 plants m -2 ) plus six treatments corresponding to maize and weed species without competition. All the means for dry matter accumulated by maize plants in the stem and leaf in the density of 15 plants m ² were higher than the means for plants in coexistence with 30 plants m -². Number of kernels, diameter and length of cob were not affected by competition with weeds. The weeds that most interfered with maize biomass production were S. arundinaceum and B. brizantha. Leaf dry mass accumulation was more sensitive than the production of stem. It was observed that maize was usually very competitive with weeds, and there was a strong decrease in dry matter accumulation of all the weeds in the study when in coexistence with the crop. Keywords

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-This study aimed at evaluating the physiology of maize and weeds when living under different densities. The randomized block design with 4 replications was used. The factorial scheme 5 x 2 + 1 and 5 x 3 was adopted, for maize and weeds respectively, corresponding to weed species (Bidens pilosa, Commelina benghalensis, Urochloa brizantha, Sorghum arundinaceum and Ipomoea triloba) and infestation density (control, 15 and 30 plants m -2 ). Weeds were kept in coexistence with the maize hybrid DKB 390 PRO 2, with an additional treatment for maize plants absent of competition. It was kept in coexistence with maize hybrid DKB 390 PRO 2 besides an additional treatment with maize plants absent of competition. On day 45 and 60 after maize planting (DAP) physiological reviews were performed within the culture, and 38 days after weed transplanting (DAT), an infrared gas analyzer (IRGA) was used. There were physiological changes in maize due to the coexistence with weeds. On day 45 DAP, the competition, regardless of the weed species, caused less photosynthetic rate in maize coexisting with 15 plants m showed lower transpiration rate. U. brizantha and S. arundinaceum showed reduction in photosynthesis and transpiration, due to increased density and coexistence with maize. Keywords

Wastewater can be considered an excellent nutritional and water source for cultivated plants. However, the presence of high concentrations of salts and toxic compounds can negatively affect crops. The effect of irrigation with different concentrations of treated wastewater on the accumulation of nutrients and gas exchange aspects of millet (Pennisetum glaucum (L.) R. Br.) grown in clay soil and sandy loam soil was analyzed. This study was conducted in a greenhouse (16°40’57,50” S; 43°50’26,07” O; 650 m) in a 5 x 2 factorial design, consisting of five levels of concentration of treated wastewater (0, 25, 50, 75, and 100%), combined with two types of soil (clay and sandy loam). The experiment was designed in randomized blocks with four replicates. The increase in treated wastewater concentration in irrigation water applied to clay soil and sandy loam soil favored the increase of net photosynthesis, transpiration rate, stomatal conductance, leaf chlorophyll content and accumulation of macro- and micronutrients in millet plants. Millet plants grown in clay soil showed an average increase of 23% in gas exchange capacity and 71% in accumulation of macro- and micronutrients, when compared with treatments in sandy loam soil. Therefore, treated wastewater contributes to the increase in gas exchange capacity and greater accumulation of nutrients in millet plants, which represents an alternative for reduced demand for fresh water and use of chemical fertilizers.

-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.Keywords: Eucalyptus, picloram, 2,4-D, photosynthetic rate, water use efficiency, bioassay. RESUMO -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 + 240 g L -

Plants have the ability to undergo morphophysiological changes based on availability of light. The present study evaluated biomass accumulation, leaf morphoanatomy and physiology of Neonotonia wightii and Pueraria phaseoloides grown in full sunlight, as well as in 30% and 50% shade. Two assays were performed, one for each species, using a randomized block design with 10 replicates. A higher accumulation of fresh mass in the shoot of the plants was observed for both species under cultivation in 50% shade, while no differences were detected between the full sunlight and 30% shade. N. wightii and P. phaseoloides showed increase in area and reduction in thickness leaf when cultivated in 50% shade. There were no changes in photosynthetic rate, stomatal conductance, water use efficiency and evapotranspiration of P. phaseoloides plants because growth environment. However, the shade treatments caused alterations in physiological parameters of N. wightii. In both species, structural changes in the mesophyll occurred depending on the availability of light; however, the amount of leaf blade tissue remained unaltered. Despite the influence of light intensity variation on the morphophysiological plasticity of N. wightii and P. phaseoloides, no effects on biomass accumulation were observed in response to light.

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A severidade de doenças em plantas pode ser afetada por práticas, como a aplicação de herbicidas para o controle de plantas daninhas. Por isso, objetivou-se apresentar e discutir a relação do uso de herbicidas na severidade de doenças de plantas cultivadas. Após contato, os patógenos tentam infectar e colonizar os hospedeiros, enquanto que estes também utilizam de mecanismos para se defender da infecção. Os tricomas, a cutícula e as ceras epicuticulares são barreiras à penetração. Compostos fenólicos, enzimas e fitoalexinas são substâncias sintetizadas pelas plantas e tóxicas aos patógenos. A ação herbicida influencia a severidade de doenças de maneira indireta sobre os mecanismos de defesa das plantas ou de forma direta, quando apresenta efeito tóxico aos patógenos. O efeito de adjuvantes presentes na formulação comercial dos herbicidas provoca degradação dos tricomas, das ceras epicuticulares e da cutícula, favorecendo a penetração dos patógenos. Efeitos prejudiciais na fisiologia e metabolismo secundário das plantas, provocados por herbicidas, afeta a síntese de compostos de defesa supracitados. Entretanto, as moléculas herbicidas podem inibir a germinação de esporos e crescimento de hifas fúngicas, o que implica na redução da infecção e colonização. Pontos necróticos decorrentes da ação herbicida podem tornar as plantas menos propensas à ocorrência de ferrugens, míldios e oídios que são causadas por fungos biotróficos. Os herbicidas ainda possuem efeitos secundários como a redução populacional de plantas hospedeiras alternativas e de insetos vetores. A relação entre herbicidas e severidade de doenças em culturas figura como importante ferramenta para o manejo fitossanitário de forma integrada.