Navegando por Autor "Ribeiro, Dimas Mendes"

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Action of ferric and aluminium ions on the dormancy breakage of Stylosanthes humilis seeds
(Acta Physiologiae Plantarum, 2011-04-05) Ribeiro, Dimas Mendes; Mapeli, Ana Maria; Delatorre, Carla Andréa; Carnelossi, Marcelo Augusto Gutierrez; Barros, Raimundo Santos
Dormancy of scarified seeds of Stylosanthes humilis was broken by acidic Al^3+ and Fe^3+ solutions. Fe^+3-stimulated seeds exhibited a high activity of 1-aminocyclopropane-1-carboxylate (ACC) oxidase and produced great amounts of ethylene, which showed correlated with the germination process. In addition, specific inhibitors of ethylene biosynthesis and action largely depressed the Fe^3+-stimulated germination, leading to the conclusion that the ion broke dormancy by triggering ethylene production by the seeds. By contrast, inhibitors of ethylene biosynthesis and action did not impair germination of Al^3+-stimulated dormant seeds. Moreover, ethylene production and activity of ACC oxidase of Al^3+-treated seeds was substantially decreased by inhibitors of ethylene biosynthesis, but germination kept large. Together these data suggest that ethylene biosynthesis was not required in the chain of events triggered by Al^3+ leading to dormancy breakage. Methyl viologen (MV), a reactive oxygen species-generating compound, broke dormancy of seeds to the same extent as Al^3+ did. Germination of both Al^3+- and MV-stimulated dormant seeds was inhibited by sodium selenate, an antioxidant compound; selenate, however had no effect on germination of Fe^3+-stimulated seeds. Together these data indicate that the mechanisms underlying the germination of Al^3+- and Fe^3+-treated seeds are not the same.
Differential root and shoot responses in the metabolism of tomato plants exhibiting reduced levels of gibberellin
(Environmental and Experimental Botany, 2019-01) Martins, Auxiliadora O.; Omena-Garcia, Rebeca P.; Oliveira, Franciele S.; Silva, Welder A.; Hajirezaei, Mohammad-Reza; Vallarino, José G.; Ribeiro, Dimas Mendes; Fernie, Alisdair R.; Nunes-Nesi, Adriano; Araújo, Wagner L.
The ability to adapt to the environment is crucial for plant survival and thus a refined communication system capable of integrating endogenous and exogenous signals and further relaying this information to different parts of the plant is a key component of such adaptability. Given that they grow in highly distinct environments it is arguably unsurprising that roots and shoots display different responses to a given environmental condition. Accordingly, a higher sensitivity of roots to gibberellins (GAs) allows rapid adjustments in growth and development possibly triggering (a) stress tolerance mechanism(s). Here we investigated the differential metabolic responses between root and shoot following reductions of the endogenous GA content using tomato (Solanum lycopersicum L.) plants deficient in GA biosynthesis (gib3, moderately deficient, gib2, intermediate deficiency and gib1, extremely deficient in GAs). GA depletion impedes shoot growth to a greater extent than root growth in all mutants. Moreover, the greater the reduction in GA content the greater the extent of a disturbance at the metabolic level. Low leaf carbohydrate contents were observed in plants displaying higher root growth, suggesting an enhanced flow of photoassimilate to support root growth. Large increases in amino acids contents of either roots or shoot were observed. The increased amino acid content was coupled to reduced levels of TCA cycle intermediates suggesting that these changes are directly linked to early reactions of nitrogen assimilation. The combined data are discussed in terms of our current understanding of the interaction between GA and primary metabolism and their crosstalk in environmental responses.
Effect of sodium nitroprusside (SNP) on the germination ofSenna macranthera seeds (DC. ex Collad.) H. S. Irwin & Baneby under salt stress
(Journal of Seed Science, 2015-10) Silva, Aparecida Leonir da; Dias, Denise Cunha Fernandes dos Santos; Borges, Eduardo Euclydes de Lima e; Ribeiro, Dimas Mendes; Silva, Laércio Junio da
Nitric oxide (NO) has been used as stimulating of the germination process for many species. However, there are few studies evaluating the effect of nitric oxide donor in the regulation of seed germination under salt stress, especially for native forest species. The objective was to evaluate the effects of SNP, an NO donor substance, on germination of Senna macranthera seeds under salt stress. The seeds were germinated at different osmotic potentials induced by NaCl solution (0.0, -0.1, -0.2, -0.3, -0.4 and -0.5 MPa). To evaluate the effect of the SNP, potentials -0.3 and -0,4 MPa were selected, applying SNP at different concentrations: 100, 200, 300 and 400 µM. Germination tests were conducted at 25 °C, with photoperiod of 8 hours. Percentage of radicle protrusion, radicle protrusion speed index, percentage of normal seedlings, shoots and roots length and dry matter were evaluated. Salt stress with NaCl is harmful to germination of S. macranthera seeds. SNP has the potential to recover germination under salt stress, especially in the concentration of 100 µM.
Effect of the seed coat on dormancy and germination in Stylosanthes humilis H. B. K. seeds
(Journal of Seed Science, 2017-04) Chaves, Izabel de Souza; Silva, Nilo Cesar Queiroga; Ribeiro, Dimas Mendes
Seed of Townsville stylo (Stylosanthes humilis H.B.K.) is known to exhibit a hard seed coat and when freshly harvested also show a physiological dormancy, however, the nature of the co-actions between seed coat and embryo growth that determine dormancy is poorly understood. In this study, physical dormancy of Townsville stylo seeds was not reduced during natural ageing at room temperature, in contrast to the physiological dormancy, which is gradually overcome during after-ripening. Furthermore, the permeability of seed coat was affected by scarification treatments as well as by low-pH solutions. Together, these data indicate that physical dormancy overcome of seed is prerequisite for radicle protrusion and physiological dormancy of Townsville stylo seeds contribute to its timing.
Effects of gibberellic acid on Tifton 85 bermudagrass (Cynodon spp.) in constructed wetland systems
(Plos One, 2018-10-26) Araújo, Edcássio Dias; Borges, Alisson Carraro; Dias, Neriamara Martins; Ribeiro, Dimas Mendes
This study aimed to evaluate 1) the influence of gibberellic acid (GA3) in the development of Tifton 85 bermudagrass grown in constructed wetland systems (CWs) and 2) the plant's capacity to remove nutrients and sodium from synthetic municipal wastewater (SMW). The experiment was carried out in Viçosa, Minas Gerais, Brazil, and consisted of foliar applications of GA3 set in randomized blocks design, with four replicates and 6 treatments as following: NC (control with plants); 0 μM GA3; N1: 5 μM GA3; N2: 25 μM GA3; N3: 50 and N4: 100 μM GA3 per CWs, NC* (control with no plants): 0 μM GA3. The study was conducted over two crop cycles in the spring 2016. The parameters used to evaluate the performance of the Tifton 85 bermudagrass were its plant height, productivity, chlorophyll measurement, number of internodes, nutrients and Na removals. Chemical analyses of the effluents were conducted. In response to the application of GA3, the increase in height of Tifton 85 bermudagrass in the first crop cycle was higher than the increase in height in the second crop cycle. The decrease in plant growth in response to GA3 in the second crop cycle may be linked to the age of the plant tissue and climatic conditions. The greater growth of the plants cultivated in the CWs allows a more efficient removal of pollutants, using simple management and low cost. The results suggest that applying 50 μM of GA3 to the development of Tifton 85 bermudagrass provides higher dry matter yield and removal of nitrogen, phosphorus, and sodium for the first crop cycle in CWs. However, in the second crop cycle, the application of GA3 had no effect on dry matter production and nutrient removal by Tifton 85 bermudagrass in CWs.
Ethylene responses and ACC oxidase gene expression in Lippia alba (Verbenaceae) chemotypes with varying ploidy levels
(In Vitro Cellular & Developmental Biology - Plant, 2017-06) Batista, Diego Silva; Castro, Kamila Motta de; Ribeiro, Dimas Mendes; Caixeta, Eveline Teixeira; Santos, Marcelo de Oliveira; Viccini, Lyderson Facio; Otoni, Wagner Campos
Lippia alba (Mill.) N. E. Br ex Britton & P. Wilson is a species of great economic importance due to the medicinal activity conferred by its essential oils. Ethylene (ET) is a gaseous hormone that affects several processes in plant growth and development. This hormone is synthesized through a reaction in which 1-aminocyclopropane-1-carboxylic acid (ACC) is converted to ET by the action of the enzyme ACC oxidase (ACO). The ET activity in three L. alba chemotypes (BGEN-01, triploid; BGEN-02, diploid; and BGEN-42, hexaploid) was evaluated by culturing plants in vitro in the presence of the ET precursor (ACC), scavenger mercury perchloride (MP), the inhibitors aminoethoxyvinylglycine (AVG) and silver thiosulfate (STS), and a CO2-enriched atmosphere. Leaf abscission rate, ET accumulation, and ACO gene expression (LaACO) were investigated. Leaf abscission was higher in BGEN-42, regardless of the precursor/inhibitor. ACC had the highest ET accumulation in BGEN-02 and BGEN-01, whereas BGEN-42 presented lower ET accumulation than the control. MP and AVG were effective in preventing ET production when compared to the control. LaACO was upregulated in BGEN-01 and BGEN-42 treated with ACC and in BGEN-01 treated with STS. In the CO2 enrichment experiments, LaACO expression was higher in BGEN-42 in the treatments without forced ventilation. Thus, the expression of this gene in L. alba can be altered by elevating CO2 levels and also by the addition of ACC. This is the first report of ET interactions in L. alba cultured in vitro.
Germinação de sementes dormentes de Stylosanthes humilis H.B.K. promovida pelo acúmulo de etileno em ambiente fechado
(Universidade Federal de Viçosa, 2003-02-25) Ribeiro, Dimas Mendes; Barros, Raimundo Santos; http://lattes.cnpq.br/5398288540393715
Sementes dormentes escarificadas de estilosante (Stylosanthes humilis HBK), leguminosa tropical forrageira anual, germinaram em ambiente fechado devido ao acúmulo de etileno por elas produzido. O etileno acumulado fez aumentar a germinação e intensificou a sua produção. A adição de etileno à atmosfera interna dos frascos Erlenmeyers selados, às concentrações 0,5 mmol m -3 ou menores, promoveu um aumento na produção de etileno, em comparação ao etileno adicionado, caracterizando um efeito autocatalítico do regulador gasoso. A remoção do etileno da atmosfera dos frascos por solução de perclorato de mercúrio levou a diminuição da emanação do regulador gasoso pelas sementes dormentes e não- dormentes e também da germinação. Os inibidores da biossíntese do etileno, 2- aminoetoxivinilglicina mais Co(NO 3 ) 2 , bloquearam completamente a germinação das sementes dormentes, mas não das não-dormentes, possivelmente devido ao etileno residual produzido por estas. A combinação das duas técnicas, isto é, remoção do etileno da atmosfera dos frascos simultaneamente à embebição das sementes com a solução dos inibidores, promoveu uma inibição completa da produção de etileno por sementes dormentes e não-dormentes e da germinação. Com a Injeção de etileno na atmosfera dos frascos Erlenmeyer, a germinação das sementes não- dormentes foi estimulada sob concentrações bem menores do que as requeridas para a germinação das sementes dormentes, indicando que a sensibilidade ao regulador gasoso foi bem maior nas sementes não-dormentes.
Germination of dormant seeds of Stylosanthes humilis as promoted by ethylene accumulation in closed environments
(Brazilian Journal of Plant Physiology, 2004-05) Ribeiro, Dimas Mendes; Barros, Raimundo Santos
Germination of scarified dormant seeds of Townsville stylo (Stylosanthes humilis) is very low in Petri dishes, but may be appreciable in sealed Erlenmeyer flasks if ethylene accumulates in their atmospheres. When ethylene in the flask atmosphere was fixed by a mercuric perchlorate solution, emanation of the gaseous regulator and germination of dormant seeds were drastically decreased. On the other hand, ethylene produced by dormant seeds and accumulated in the flask atmosphere led to a further enhancement of ethylene accumulation and a corresponding increased seed germination. Germination of both dormant and non-dormant seeds did not occur when ethylene biosynthesis was completely blocked.
Re-evaluation of the role of nitric oxide as a component of abscisic acid signalling pathway in guard cells
(Universidade Federal de Viçosa, 2007-04-13) Ribeiro, Dimas Mendes; Finger, Fernando Luiz; http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4783681Y0; Puschmann, Rolf; http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4787733Y5; Barros, Raimundo Santos; http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4787859T6; http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4778644J9; Dias, Denise Cunha Fernandes dos Santos; http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4727304Z9; Fontes, Elizabeth Pacheco Batista; http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4781848H2; Oliveira, Luiz Edson Mota de; http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4783250P2; Loureiro, Marcelo Ehlers; http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4780851Y3
O ácido abscísico (AAB), sintetizado em resposta ao défice hídrico, induz o fechamento dos estômatos via ativação de uma complexa cascata de sinalização. Tem-se demonstrado que o óxido nítrico (ON) é um componente chave na cadeia de sinalização que leva ao fechamento dos estômatos induzido pelo AAB em várias espécies, sob boa disponibilidade hídrico. Entretanto, a função do ON no fechamento dos estômatos induzido pelo AAB em resposta ao défice de água não está esclarecida. O AAB induz a formação de ON e a remoção do ON por um seqüestrador inibe o fechamento dos estômatos em folhas túrgidas, mas não nas desidratadas. A síntese de ON induzida pela redutase do nitrato (RN) parece necessária para o fechamento dos estômatos induzido por AAB em folhas túrgidas de Arabidopsis, mas não nas desidratadas. Além disso, as células-guardas de folhas túrgidas do duplo mutante da RN nia1 nia2 e do mutante simples da RN nia1::Ds não sintetizam ON e nem fecham os estômatos em resposta ao AAB ou nitrito, embora os estômatos desses mutantes se feche em resposta ao NPS (nitroprusado de sódio), composto liberador de ON. Entretanto, o fechamento dos estômatos do mutante nia1 nia2 e nia1::Ds foi induzido por AAB, mas não por nitrito ou NPS em folhas mantidas sob défice hídrico, indicando que o fechamento dos estômatos induzido por AAB ocorreu independentemente da síntese de ON mediada pela RN. Confirmando esses resultados, o AAB reduziu a perda de água nos mutantes nia1 nia2 e nia1::Ds, e também em plantas do tipo selvagem, mas NPS e nitrito não diminuíram a transpiração das folhas dos mutantes deficientes na RN e em folhas do tipo selvagem. O tratamento de folhas de mutantes insensíveis ao AAB, abi1-1 e abi2-1, com AAB ou NPS não promoveu qualquer alteração significativa na abertura dos estômatos em folhas tanto sob condições de défice hídrico como em folhas não estressadas, sugerindo que o ON foi incapaz em sobrepor-se à mutação abi1-1 e abi2-1. Assim, o ON não parece necessário para o fechamento dos estômatos induzido pelo AAB em folhas sob condições de défice de água.