RESUMO:As plantas daninhas, de forma geral, causam transtornos e prejuízos para diversos agricultores.O capim-navalhão (Paspalum virgatum) tem se destacado como uma agressiva planta daninha de pastagens em diversas regiões, especialmente em áreas de solo mais úmido. A sua baixa palatabilidade, grande produção de semente, tolerância a diferentes condições de estresse ambiental, e principalmente sua semelhança morfológica, fisiológica e bioquímica com as gramíneas forrageiras dificultam seu controle. O conhecimento da capacidade germinativa das sementes de plantas daninhas pode gerar subsídios para a adoção de práticas de manejo, visando reduzir sua população em ambiente agrícola ou de criações.O presente trabalho objetivou estudar os aspectos germinativos das sementes de capim-navalhão, visando avaliar a superação de dormência de suas sementes nos seguintes tratamentos: escarificação química utilizando ácido sulfúrico (H 2 SO 4 ), por 1, 5 e 15 minutos; embebição em água em temperatura ambiente por 2, 4, 8 e 16 horas; embebição em hipoclorito de sódio por 1, 5, 10 e 15 horas; e armazenamento em temperatura elevada (40 ºC) por 0, 23, 28, 33 e 38 dias. Assim, nas condições experimentais deste estudo, o uso de escarificação química proporcionou a maior percentagem e índice de velocidade germinativa de sementes de P. virgatum, assim como o método de armazenamento em temperatura elevada (40 ºC), especificamente por 23 e 33 dias.Temperaturas elevadas, tais como ocorrem no solo podem contribuir para a quebra de dormência das sementes capim-navalhão, assemelhando-se ao ato dos ruminantes ao se alimentarem das partes da gramínea, passando pelo trato digestivo,que possui efeito semelhante ao do ácido sulfúrico, contribuindo assim para que ocorra a quebra de dormência e,posteriormente disseminam as sementes da espécie. Palavras chave: Paspalum virgatum.planta daninha.Germinação.temperatura elevada.hipoclorito de sódio.
-The objective of this work was to evaluate seeds of cowpea, cultivar BRS Tumucumaque, subjected to different water stresses induced by polyethylene glycol (PEG-6000) and mannitol and different salt stresses induced by NaCl and CaCl 2 solutions. The water and salt stresses was evaluated in laboratory using completely randomized experimental designs in 2x6 factorial arrangements, with six osmotic potentials (0.0, -0.2, -0.4, -0.6, -0.8 and -1.0 MPa) and two stress inducers for each experiment, with four replications of 50 seeds. The percentage of germination, germination speed index, root and shoot lengths and seedling fresh weight were evaluated at the tenth day (end of the evaluation period). The simulated water stress showed effects on the cowpea seed germination and seedling initial growth by decreasing the rates of the variables evaluated, which had greater effect in treatments with PEG-6000. The salt stress induced by NaCl showed greater effect on the variables evaluated than that induced by CaCl 2 , due to the sodium toxicity in the salt chemical composition.Keywords: Germination speed index. Water deficit. Osmotic potential. ESTRESSE HÍDRICO E SALINO NA GERMINAÇÃO DE SEMENTES DE FEIJÃO-CAUPI (Vigna unguiculata cv. BRS Tumucumaque)RESUMO -O objetivo deste trabalho foi avaliar o comportamento de sementes das sementes da cultivar de feijão-caupi BRS Tumucumaque sob efeito de potenciais hídricos provocados por polietileno glicol (PEG 6000) e manitol e de potenciais salinos induzidos por soluções de NaCl e CaCl 2 . Para verificação dos estresses hídrico e salino, avaliou-se em laboratório, a combinação de seis potenciais osmóticos (0,0; -0,2; -0,4; -0,6; -0,8 e -1,0 MPa) com os dois agentes de estresses para cada experimento, em delineamento inteiramente casualizado, configurando esquema fatorial 2x6, com quatro repetições de 50 sementes. Foram avaliadas as variáveis: porcentagem de germinação, índice de velocidade de germinação (IVG), comprimento de raiz e parte aérea e massa fresca de plântulas no décimo dia, ao final do período de avaliação. A simulação de deficiência hídrica, utilizando-se manitol e PEG 6000 permitiu a constatação dos efeitos do estresse na germinação e no crescimento inicial das plântulas da cultivar BRS Tumucumaque, pelo decréscimo das variáveis observadas, sendo que os tratamentos à base de PEG 6000 foram os mais drásticos. A indução do estresse salino pelos sais NaCl e CaCl 2 foi verificada nas variáveis avaliadas, onde os efeitos do NaCl foram mais acentuados, devido a toxidade do sódio na composição química do sal.Palavras-chave: Índice de velocidade de germinação. Restrição hídrica. Potencial osmótico.
The practice of liming may influence the leaching of herbicides in soils, especially those with weak acid character, such as picloram. The study on leaching, preserving soil structure, is an important factor when one intends to understand the dynamics of herbicides and environmental impacts. Thus, the effect of liming on picloram leaching in a dystrophic Red Yellow Latosol under field conditions was studied using a bioindicator plant. The experiment was set up in a completely randomized design (CRD), in split-plot scheme, with factorial in the plot. The factors of the plot corresponded to two soil conditions (presence and absence of liming) and 5 picloram concentrations (0; 384; 768; 1152; 1536 g ha-1), and the factor of the subplot was 5 soil depths (0-8, 8-16, 16-24, 24-32 and 32-40 cm), with four replicates. Pipes were introduced into the soil and, in part of the treatments, limestone was applied superficially. After ninety days, the different doses of picloram were applied on the surface of each pipe and these pipes were withdrawn after an accumulated rainfall of 128 mm, to perform the bioassay using cucumber plants (Cucumis sativus). Evaluations of plant development (phytotoxicity and shoot biomass) were carried out 21 days after sowing. It was concluded that picloram showed high leaching rate under all studied conditions and liming increased picloram leaching at doses lower than 768 g ha-1.
The corn crop has been cultivated throughout the country, with increasing productivity with the help of technology products. There are greater demand and greater use of improved seeds, associated with treatments of fungicides, insecticides, and bioregulators. It is believed that the use of biostimulant can improve many plant characteristics, one of which is productivity. The present work had as objective to evaluate the effect of the use of biostimulant applied in the treatment of seeds on the germinability and initial development of corn plants. The biostimulants used in the experiment were the Haf-Plus ® from the Inesta group, which is an organomineral stimulant and Stimulate ® from Stoller do Brazil which is a hormonal bio stimulant. The experimental design was completely randomized, in a 2 x 4 factorial scheme, with two biostimulants (Stimulate ® and Haf Plus ®) in 4 doses (Stimulate: control, 0.5 mL of Stimulate + 1 mL of water, 1.0 mL of Stimulate + 0.5 mL of water, 1.5 mL of Stimulate, and for Haf Plus: control, 0.125 mL + 0.375 mL of distilled Original Research Article
Changes in global climate have an important relationship with CO2 emission into the atmosphere. The implementation of integrated systems in some regions in the Amazon can mitigate CO emissions and improve soil attributes in the medium to long term. In this context, this study aimed to evaluate the CO emission dynamics and its relationship with soil attributes under different uses in the Amazon. The experiment consisted of four treatments characterized by different land uses (Degraded Pasture – DP, Managed Pasture – MP, Native Forest – NF, and Livestock Forest Integration – LF), with 25 replications. Soil CO emission (FCO ), soil temperature (Ts), and soil moisture (Ms) were evaluated over a period of 114 days. Soil samples were collected at the end of this period at a depth of 0 to 0.20 m to determine soil chemical, physical, and biological attributes. The mean FCO reached values of 3.80; 4.44; 3.88; and 3.14 µmol m s in NF, DP, MP, and LF, respectively. In addition to the direct relationship between soil CO emissions and soil temperature for all land uses, soil density indirectly influenced emissions in NF. The amount of humic acid induced the highest emission in DP. The increase in H+Al contents and the reduction in microbial biomass carbon increased emissions in MP. The highest CO emissions came from DP, which had the lowest values of soil moisture and the highest values of soil temperature. Soil organic carbon and carbon stock were higher in MP (8.20 g kg and 21.49 g kg ) and LF (6.01 g kg and 16.12 g kg ), respectively. These values demonstrate that FCO was influenced by the Amazon land uses and highlight LF as a low CO emission system with a higher potential for carbon stock in the soil
The presence of weeds amid pastures has caused significant damage to cattle farmers due to the difficulty in controlling these species. Paspalum virgatum stands out as an aggressive weed in Amazonian agroecosystems. Proper management of weed species is threatened by their aggressiveness, adaptation to low fertility soils and morphological, physiological and biochemical similarities with the grasses used as fodder. It is also possible that part of these characteristics of aggressiveness occur due to the ability of weeds to produce allelochemicals, resulting in damage to surrounding plants. The objective of this study was to qualitatively verify the presence of secondary metabolites in P. virgatum species under different water availability. The analyzed species were initially grown separately under three conditions of water availability: water deficit, field capacity and flooded environment. The water deficit treatment was conducted to verify weed ability to develop under conditions of extreme water shortage. This is a characteristic related to its rusticity, as found in grasses in the Amazon region. Excess water treatments were also conducted, since this is a common condition found in areas with partial flooding of a few months during the rainy season in the Amazon. After 120 days, weeds were collected and separated into roots, stems and leaves. The material was subsequently dried, ground and subjected to procedures to determine secondary metabolites. Phenolic compounds, flavonoids and alkaloids were identified in all conditions of plant development. The flavonoid detection test presented an intense yellow color. This is a strong indication of the presence of this class in stems and leaves of plants under flood and in leaves of plants under field capacity soil conditions. An intense presence of phenolic compounds was verified in stems and leaves, regardless of treatment. General alkaloids were found in great intensity in all samples. Saponins were found in leaves of P. virgatum under water stress (flooding and water deficit). All the metabolites were found in the plants, diverging between treatments and parts of the plant. It was concluded that the species presented higher steroid content in the roots when growing in places with excess of water. In conditions of full water supply, the presence of steroid was less intense in the roots, leaves and stems, result also found in roots and leaves of plants under water deficit. Alkaloids were less intensely present in the roots, regardless of the water treatment in which the plant was submitted. Results demonstrated that there are secondary metabolites responsible for some physiological ability of the weed to withstand excess or water deficit, indicating the need for further studies
Sunflower is a crop of great economic interest both nationally and internationally, due to its use especially in oil production. However, factors such as water restriction are commonly found in growing areas and exert a negative influence on the productive performance of the crop, especially in critical periods, such as the germination and initial development of the seedlings. Thus, the objective of this study was to evaluate the germinate behavior of seeds of sunflower cultivars as a function of lower osmotic potentials. The experiment was installed in a completely randomized design, in a 3x5 factorial scheme, three sunflower cultivars (Charrua, Nussol and Olisiun 4) and five osmotic potentials (0, -0.2, -0.4, -0.8, -1.2 MPa) with 3 replicates. For the study, solutions of polyethylene glycol (PEG 6000) were repaired. Rolls of paper towels were moistened with the concentrations and later kept in a germination chamber at 25 °C, where they remained for ten days. First counts (4th day) and total counts (10th day) were performed, and the germination rate (%) was verified. In addition, in the last evaluation, aerial and root length, green mass and dry mass of seedlings were determined. Based on the results obtained it can be verified that in osmotic potential higher than -0.8 MPa, no germination occurred. Nussol germinated more in more negative concentrations, with a germination rate of 90%, differing from the cultivars Charrua and Olisiun 4, which, in larger potentials, reached only 30% of germination.
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