O presente trabalho teve como objetivo caracterizar a dinâmica da comunidade infestante de plantas daninhas em cultivo do feijão-caupi no semiárido mineiro. Os tratamentos consistiram na coleta das plantas daninhas aos 7, 14, 21, 28, 35, 42, 49, 56, 63 dias após a emergência (DAE), posteriormente foi feito o controle da comunidade infestante por capina mecânica. A coleta de plantas daninhas foi feita pelo método padrão do quadrado inventário, lançado aleatoriamente na área útil de cada parcela, recolhendo todas as plantas. Foram determinados o número de indivíduos por espécie em cada parcela e o número total por coleta. Após a identificação e contagem das espécies, foi realizado o cálculo das variáveis fitossociológicas: Frequência, Densidade, Abundância, Frequência relativa, Densidade relativa, Abundância relativa, Dominância relativa, Índice de valor de importância (IVI), Índice de valor de cobertura (IVC) e Índice de similaridade (IS). As espécies Portulaca oleracea, Amaranthus viridis e Sorghum bicolor apresentaram maiores valores de IVI. Foi possível afirmar que é alta a similaridade florística das espécies de plantas daninhas que ocorreram durante o ciclo do feijão-caupi. Quanto ao Índice de valor de Cobertura (IVC), destacaram-se as espécies Portulaca oleracea, Sorghum bicolor e Senna obustifolia. Palavras-chave: comunidade infestante; Vigna ungiculata; levantamento fitossociológico. Phytosociology of weeds in cultivation of cowpea in the semi-arid region of Minas Gerais ABSTRACT: The present work aimed to characterize the dynamics of the weed community in cultivation of cowpea in the semi-arid region of Minas Gerais. The treatments consisted of collecting the weeds 7, 14, 21, 28, 35, 42, 49, 56, 63 days after emergence (DAE); following each collection, the weed community was controlled by mechanical weeding. The collections were carried out using the standard method of the inventory square, randomly launched in the useful area of each plot, collecting all the plants. The number of individuals per species in each plot and the total number per collect were determined. After identifying and counting the species, the phytosociological variables were calculated: Frequency, Density, Abundance, Relative frequency, Relative density, Relative abundance, Relative dominance, Importance value index (IVI), Coverage value index (CVI) and Similarity Index (SI). The species Portulaca oleracea, Amaranthus viridis and Sorghum bicolor presented the largest IVI. It was possible to affirm that the floristic similarity of the weed species that occurred during the cowpea cycle is high. The species Portulaca oleracea, Sorghum bicolor and Senna obustifolia presented the highest CVI values. Keywords: infestant comunnity; Vigna ungiculata; phytosociological survey.
Sorghum is one of the most drought-tolerant cereals. However, strong water stress, especially during the reproductive phase, causes significant grain yield reduction. Drought events are common in second crops planted after soybean harvest in Brazil. The objective of the present study was to assess grain sorghum hybrids grown under pre- and post-flowering drought stress. Twenty-five hybrids were subjected to two water stress environments (pre- and post-flowering) and one environment with non-water stress. The experimental design was a split plot based on a randomized complete block with three replicates. Water stress pre-flowering reduced plant height, accelerated flowering, and increased panicle index compared with water stress post-flowering. Both pre- and post-flowering stress reduced yield, by 45% and 48%, respectively. Grain mass was greatly affected by stress occurring post-flowering but not by that occurring pre-flowering. Therefore, the reduction in yield caused by pre-flowering stress is due more to the reduction of grain number in the panicle, whereas the reduction when stress occurs post-flowering is due more to reduction in grain size. The plant chlorophyll index decreased when stress occurred pre-flowering and reverted after irrigation had resumed, demonstrating recovery in the photosynthetic capacity of the sorghum plant. With post-flowering stress, the chlorophyll index decreased significantly 30 days after the stress, affecting grain filling, with consequent yield loss
The objective was to identify the species and quantify the importance value index of weeds in the cultivation of arabica coffee in two irrigation systems, at different times of the year, in the northern region of Minas Gerais. A phytosociological survey was carried out in each season of the year (spring, summer, autumn and winter) in an area cultivated with the species Coffea arabica, subjected to two irrigation systems (sprinkling and dripping). The coffee crop was implanted at a spacing of 3.5 m between rows and 0.7 meters between plants. The collection of weeds was performed using the standard method of the square inventory, which was launched between the lines of the crop. The identification of the species was carried out, the number of individuals was quantified, the dry mass, frequency, density, abundance, importance value index and coverage, and the similarity index. 33 weed species were identified, being the species with the highest IVI Euphorbia hirta, Brachiaria plantaginea, Digitaria horizontalis, Cyperus rotundus and Amaranthus spp. It was observed a higher occurrence of weeds from the monocot group in the sprinkler irrigation system while in the drip there were predominance of dicot plants.
Selection for drought tolerance is one of the main challenges of sorghum breeding programs, and early phenotyping, in the seedling phase, can increase selection gains for this trait. This work evaluated characteristics related to root morphology as indicators for early selection of tolerant genotypes to water restriction. Twenty-six hybrids were evaluated, of which twenty-three were experimental and three commercial (BRS310, DKB540 and 1G282). The hybrids were grown in tube-shaped containers in a greenhouse with non-stress stressed water. The evaluated characteristics were Root length (RL), root surface area (SA), root diameter (RD), root volume (RV), surface area of very thin roots (from 0-1 mm in diameter) (SA1), as well as the root/shoot dry mass ratio (R/S). Under water restriction, the hybrids with the best performances for most of the evaluated characteristics were BRS310, 1516057, 1719034, 1719026, 1716041, 1G282, 1516059, 1720052, 1716049, 1718036 and 1716045. The characteristics RV, SA, SA1 and R/S showed the greatest contribution in the selection of these hybrids.
The banana is a highly perishable fruit in which storage and transport for a long period is limited due to the lack of post-harvest technologies that aim to retard fruit ripening. In this regard, the objective of this study was to evaluate the postharvest conservation period of the ‘Prata-Anã’ clone Gorutuba banana using different concentrations of 1-methylcyclopropene (1-MCP), associated with the modified atmosphere and refrigerated storage. Banana bunches (Musa spp. AAB) ‘Prata-Anã’ Gorutuba clone were obtained from Belém farm, located in Janaúba-MG. The pieces were decomposed in bouquets of 4 fruits and submitted to 1-MCP application at concentrations of 0.0; 0.2; 0.4; 0.6; 0.8 and 1.0 ppm for 24 hours and stored refrigerated at room temperature to 13±1 °C. Every 5 days physical and chemical evaluations were performed. There was a delay in the ripening of fruits subjected to refrigeration and treated with 0.6 ppm of 1-MCP and increase in shelf life, due to probable inhibition of ethylene, which showed firmer fruits. Respiratory activity decreased with increasing concentration of 1-MCP. In refrigerated storage, fruits treated with 1-MCP were kept longer than 30 days. For the fruits kept at room temperature shelf life was 21 days for fruit subjected to concentrations of 0.4 to 1.0 ppm. However, the use of 1-MCP associated with the modified atmosphere under refrigeration directly influenced the postharvest conservation of bananas, allowing a longer period of commercialization.
Uma boa formação de pastagens começa pela qualidade da semente forrageira. O uso de sementes de baixa qualidade e a escolha indevida da forrageira influenciará diretamente na formação inicial do pasto. No entanto, as espécies forrageiras tropicais exibem algumas dificuldades, como a desuniformidade na maturação e dormência nas sementes, cujo aspectos como natureza, intensidade e persistência não estão totalmente esclarecidos. Além disso, a degrana natural das sementes é uma outra limitação à produção de sementes de espécies forrageiras tropicais, o que diminui a eficiência dos métodos de colheita e prolonga a emissão da inflorescência. Um dos principais problemas relacionados a comercialização de sementes forrageiras tropicais é a estacionalidade característica do mercado, a qual está intimamente associada à época de plantio de pastagens, que ocorre no período de chuvas. Outra dificuldade é ausência de informação legal sobre o uso alternativo para as sobras e descartes de sementes forrageiras quando não atendem os padrões mínimos de qualidade para comercialização.
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