Variations in environmental conditions, such as the availability of light, can affect the efficacy of herbicides because they alter the biological characteristics of plants including those that are related to the plant’s sensitivity to herbicides. Therefore, the objective of the present study was to assess the influence of environments with different light availabilities, and of the application of glyphosate and carfentrazone-ethyl (separately or in combination) on the morphophysiology and control of Macroptilium atropurpureum. An experimental design of randomized blocks with five replicates was used, with treatments arranged in a split-plot design. The plots were composed of three levels of shading (full sunlight, 50% shading, and 70% shading); within each plot there were sub-plots, one for each of the two herbicides (glyphosate and carfentrazone-ethyl), used either separately or in combination. The doses of glyphosate + carfentrazone-ethyl applied in the treatments were 0+40 g ha-1 of carfentrazone-ethyl, 1.440+0 g ha-1 of glyphosate, 1.080+30 g ha-1 of glyphosate + carfentrazone-ethyl, and there was an additional treatment that did not include the application of an herbicide. Plants of M. atropurpureum cultivated under shading exhibited higher sensitivity to the herbicides, greater leaflet area, and lower photosynthetic rates than plants cultivated under full sunlight conditions. Under shading, both herbicides applied separately or in combination were effective in controlling M. atropurpureum, which indicates a greater susceptibility of this species to these herbicides in environments with light restriction. The species was tolerant to the two tested herbicides, used either alone or in combination, when grown under full sunlight conditions.
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.
A utilização de biofertilizante na agricultura é uma alternativa promissora aos fertilizantes minerais e de destino de dejetos. Objetivou-se neste estudo avaliar características morfológicas, produção de biomassa e teores de nutrientes foliares do milho e do milheto irrigados e adubados com biofertilizante suíno. Foram conduzidos dois experimentos, com milho e com milheto no período de junho a setembro de 2011 em um latossolo vermelho amarelo, em delineamento de blocos casualizados, com seis tratamentos e quatro repetições, a saber: doses de biofertilizante suíno para fornecer 0, 50, 100, 150 e 200 kg/ha de P2 O5 , e um tratamento adicional com adubo mineral NPK 4-14-8. Cada uma das doses de fósforo fornecida pelo biofertilizante suíno foi comparada, pelo teste de Dunett, ao tratamento adicional com adubo mineral, e a significância foi declarada quando P<0,05. Para as doses de fósforo fornecidas via biofertilizante suíno foram ajustadas equações de regressão. As plantas de milho e milheto responderam de forma linear, quanto à produção de biomassa, com o aumento das doses de biofertilizante suíno. Na dose de biofertilizante suíno que proporcionou a aplicação de 150 kg/ha de P2 O5 , a produção de biomassa para silagem e os teores foliares de nutrientes, tanto do milho quanto do milheto, foram semelhantes aos obtidos com a adubação mineral.
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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