Roberto Fontes Araujo

Teste de condutividade elétrica para sementes de feijão-mungo-verde

Good quality seeds are indispensable for successful crop establishment. A more precise analysis of seed quality requires a complementation of the information supplied by the germination with vigor tests to allow selection of the best lots for commercialization and sowing. Among these tests, the electric conductivity test is important. The objective of this study was to develop a suitable methodology for the electric conductivity test in mung bean seeds, with treatments of different imbibition periods and seed numbers. Six seed lots were used with the following treatments: 100, 75 and 50 seeds imbibed in 75 mL of 25 °C distilled water, and evaluations after 3, 6, 9, 12, and 15 hours of imbibition. The electrical conductivity test done with four subsamples of 50 pure seeds soaked in 75 mL of distilled water at 25 °C, permits a separation of the lots after three hours of soaking, and this procedure would make a quality evaluation of mung bean seeds viable.

Uso de hipoclorito de sódio para degradação do endocarpo de sementes de cafeeiro com diferentes graus de umidade

The objective of this study was to evaluate the combinations between sodium hypochlorite concentrations and presoaking times that would provide higher germination of coffee seeds with moisture contents from 13 to 33% (w.b.). The seeds of Catuai Vermelho IAC 44 variety were dried in the shade until they reached the desired moisture contents. Five assays were accomplished, one for each moisture content of the seeds (13, 18, 23, 28 and 33%). Each assay consisted of 12 treatments, each one consisting of combinations of five sodium hypochlorite concentrations (3, 4, 5, 6 and 7% active chlorine) in the presoaking solution and two presoaking times (3 and 6 hr), besides the seeds with or without endocarp that were manually removed (control). The seeds were evaluated, by using the following tests: first germination counting, germination, germination speed index and seedling vigor. According to the results, the presoaking of the coffee seeds into sodium hypochlorite at 6% concentration active chlorine for three hours promoted an efficient degradation of the endocarp, besides providing germination speed index similar to the control, when seeds showed initial moisture content between 23 and 33%. In those seeds with moisture content at 18 and 13%, the presoaking in sodium hypochlorite led to an inferior germination performance of the seeds relative to the seeds without endocarp that was manually removed, regardless of the combination between concentration and the presoaking time.

Effects of different types of drying on the physiological quality of physic nut seeds.

Objetivou-se no presente trabalho avaliar diferentes tipos de secagem e seus efeitos na qualidade fisiologica de sementes de pinhao manso (Jatropha curcas L.). As sementes, com teor de agua de 32%, foram secas a sombra ate 9,9%, ao sol ate 8,8% e em estufa de circulacao forcada as temperaturas de 33 °C ate 8,5% e 43 °C ate 8,3% A qualidade fisiologica das sementes foi avaliada pelos testes de germinacao, primeira contagem de germinacao, condutividade eletrica, envelhecimento acelerado, emergencia em areia e indice de velocidade de emergencia. A temperatura de 43 °C proporcionou secagem mais rapida das sementes, com duracao de 42 horas. Nas secagens a 33 °C, ao sol e a sombra, este periodo foi mais prolongado, com 54, 144 e 456 horas, respectivamente. A secagem a sombra proporcionou reducao na qualidade fisiologica das sementes. As sementes secadas ao sol ou a temperatura de 33 °C nao diferiram entre si quanto a qualidade fisiologica e foram superiores aquelas secadas a sombra; entretanto, a germinacao foi inferior aquelas secadas a 43 °C, a partir dos 180 dias de armazenamento. A secagem a temperatura de 43 °C nao afetou a germinacao das sementes e reduziu ligeiramente o vigor, mesmo apos 270 dias de armazenamento. Como a maior temperatura utilizada nao afetou a germinacao das sementes, isto sugere ter sido o tempo gasto na secagem das sementes e determinante para sua conservacao. Sementes de pinhao manso podem ser secadas ao sol e sob temperaturas de 33 e 43 °C; temperatura de 43 °C proporciona menor tempo de secagem e melhor germinacao e vigor de sementes de pinhao manso; secagem a sombra e prejudicial a qualidade de sementes de pinhao manso.

Maturação de sementes de milho-doce: grupo Super Doce

The objective of the experiment was to study the seed maturation process of sweet corn BR 400 cutivar (Super Sweet). The first seed harvest was accomplished 27 days after flowering (DAF), which was considered when approximately 50% of the plants presented female flowers. Other harvests were accomplished at seven day intervals up to 90 DAF. Immediately after the harvest, the seed was threshed manually, and the seed moisturety content and dry weight were determined; the presence of the black layer was also evaluated visually. After the last harvest, the physiological seed quality was determined by the following tests: germination, modified cold, accelerated aging and electric conductivity. Seed dry matter (mass maturity) reached the maximum at approximately 41 DAF and the seed germination and vigor (physiologic maturity) maximum occurred from 48 to 76 DAF. All the seeds presented black layer at 55 DAF, and this was an efficient visual characteristic for the identification of the seed physiologic maturity.

Qualidade fisiológica de sementes de milho-doce colhidas em diferentes épocas

Sweet corn seeds, compared to those of the common corn, have, in general, a thinner pericarp, which makes them more susceptible to mechanical damages. A study concerning the maturation process of sweet corn seeds was carried out to determine the ideal harvesting point in order to obtain high quality seed, as well as to evaluate the performance of the seeds when harvesting is delayed. Sowing was accomplished on December and harvests carried out on February and March. The first harvesting was performed 26 days after flowering (DAF), when approximately 50% of the plants showed female flowering. The other harvests were accomplished at 7-day intervals, until 96 DAF. After harvest, the seeds were hand threshed, moisture content and dry matter were determined, and a visual evaluation for the presence of the black layer was made. After the last harvest, physiological quality of the seeds was determined by germination, modified cold, accelerated aging and electrical conductivity tests. The harvesting of the Doce Cristal sweet corn cultivar should be accomplished from the 47th to the 75th DAF in order to obtain seeds of high physiological quality. The black layer is an efficient visual characteristic for identification of their physiological maturity.

Superação da dureza de sementes e frutos de Stylosanthes scabra J. Vogel e seu efeito na germinação

This study was carried out to evaluate methods of breaking Stylosanthes scabra seed and fruit hardness, separately. The methods evaluated were: control dry heat at 85°C for 10, 12, and 14 hours, immersion in concentrated sulphuric acid for five and 10 minutes, and immersion in boiling water for one minute. The germination test consisted of evaluating normal seedlings (germination percentage), abnormal seedlings, hard seeds and dead seeds. It was concluded that the best treatment was seed scarification with concentrated sulfuric acid for five and 10 minutes. In relation to fruit scarification, an immersion time longer than 10 minutes deserves further study. The dry heat treatment did not overcome the impermeabily of the seed covering layers. Boiling water led to the death of more than 90% of the seeds.This study aimed to evaluate the efficiency of the accelerated aging test at different periods and exposure temperatures in evaluation of the physiological seed quality of sweet corn lots. The assays were carried out from February to June 2000 at the Laboratorio de Sementes of the Phytotechny Department in the Universidade Federal de Vicosa - MG. Corn seeds of the cultivar BR 400 (Super-Doce) were used into four lots obtained from a drying process at 30, 40, 50 and 60oC and an environmental relative humidity of 60%. Initially the moisture content of the seeds was determined and then the seed physiologic quality were evaluated by the germination, first germination count and cold tests. The entirely randomized experimental design was used for these tests. Two experiments were carried out in evaluating the methodology of the accelerated aging test. The first experiment was carried out at 42oC temperature on an entirely randomized design and a factorial scheme 4x4 (four aging periods: zero, 48, 72 and 96 hours and four seed lots) arranged on a split-plot design over time. The second experiment was carried out at 45oC temperature by using the same design and a factorial scheme 4x4 (four aging periods: zero, 24, 48 and 72 hours and four seed lots). In both experiments, the 45oC temperature and the 24hour-exposure to the accelerated aging provided a better differentiation among lots with different quality levels. The 42oC temperature over a 72 hour-period allowed a better differentiation between seed lots as to their physiologic quality.

Teste de envelhecimento acelerado em sementes de crambe (Crambe abyssinica Hochst), cultivar FMS Brilhante

A utilizacao de sementes de alta qualidade fisiologica merece destaque na instalacao de qualquer cultura, sendo necessario avalia-las por meio dos testes de germinacao e de vigor. O objetivo deste trabalho foi avaliar a eficiencia do teste de envelhecimento acelerado na determinacao do vigor de sementes de crambe. Foram utilizados cinco lotes de sementes de crambe, cultivar FMS Brilhante, e a qualidade inicial de cada lote foi avaliada pela determinacao do teor de agua, germinacao, primeira contagem de germinacao, emergencia de plântulas e indice de velocidade de emergencia. Para o teste de envelhecimento acelerado, as sementes foram submetidas a temperaturas de 41 e 43 oC, em câmara tipo BOD, durante 48, 72 e 96 horas. No final de cada periodo de envelhecimento, as sementes foram colocadas para germinar, conforme metodo descrito para o teste de germinacao. O delineamento experimental foi inteiramente casualizado, com quatro repeticoes por lote. O teste de envelhecimento acelerado na condicao de 41 oC, por 72 h, proporciona maior diferenciacao do vigor entre os lotes de sementes de crambe, cultivar FMS Brilhante.

Teste de condutividade elétrica para sementes de pinhão-manso (Jatropha curcas L.)

EnglishIn order to have more accurate information of seed quality among different seed lots, it is necessary to supplement the data supplied by the germination test with other tests, making possible the selection of best lots for marketing and seeding establishment and among those tests the electrical conductivity test fits well to that purpose. For physic nut (Jatropha curcas L.), no information about electrical conductivity test methods is available in the literature. Thus, the aim of this research was to establish a standard method for testing the electrical conductivity of physic nut seeds leaking, testing different number of seeds, amount of water and soaking period. So, we used eight lots of physic nut seeds proceeding the electrical conductivity test with the following variations: 15, 25 or 35 seeds, soaked in 75 or 100 mL of distilled water at 25 oC, and the readings performed after 3, 6, 9, 12, and 24 hours of soaking. As a matter of fact, were determined the germination percentage and the seedling emergence rate. Based on the results and on the correlation coefficients calculated between the results of electrical conductivity test and emergence percentage, the most efficient methods were with 15 seeds under soaking in 75 mL of water, with readings after 6, 9 and 12 hours; 25 seeds under soaking in 75 mL of water, with readings at the same time mentioned before, but the most appropriate method to to distinguish physic nut seed lots with different physiological quality is the use of 15 seeds in 75 mL of water, with reading after six hours of its starting. portuguesPara uma analise mais completa da qualidade de sementes, faz-se necessario complementar as informacoes fornecidas pelo teste de germinacao com testes de vigor, possibilitando, assim, selecionar os melhores lotes para comercializacao e semeadura. Dentre esses testes, destaca-se o de condutividade eletrica. Para sementes de pinhao-manso (Jatropha curcas L.), nao ha informacoes referentes a metodologia do teste de condutividade eletrica na literatura. Objetivou-se neste trabalho estabelecer metodologia para o teste de condutividade eletrica em sementes de pinhao-manso, variando-se o numero de sementes, a quantidade de agua e o periodo de embebicao. Para tanto, foram utilizados oito lotes de sementes de pinhao-manso, e o teste de condutividade eletrica foi realizado com as seguintes variacoes: 15, 25 ou 35 sementes, embebidas em 75 ou 100 mL de agua destilada a 25 oC, sendo as leituras realizadas apos 3, 6, 9, 12, e 24 horas de embebicao. Para efeito de comparacao, foram determinadas a porcentagem de germinacao e a porcentagem e indice de velocidade de emergencia. Com base nos resultados obtidos e pelos coeficientes de correlacao calculados entre os resultados de condutividade eletrica e porcentagem de emergencia, verificou-se que as metodologias mais eficientes foram com 15 sementes e 75 mL de agua, com leituras apos 6 horas, 9 horas e 12 horas e 25 sementes e 75 mL de agua, com leituras, tambem, apos 6 horas, 9 horas e 12 horas. Concluiu-se que o teste de condutividade eletrica foi eficiente para diferenciar lotes de pinhao-manso quanto a qualidade fisiologica das sementes. A metodologia mais adequada para a realizacao do teste de condutividade eletrica para sementes de pinhao-manso e a conduzida com o uso de 15 sementes e 75 mL de agua, com leitura apos 6 horas de embebicao.

Índices para avaliar o estado de nitrogênio da batata multiplicada por distintos materiais propagativos

Melhoria na eficiencia de aplicacao do N pode ser conseguida pela sincronizacao da demanda da planta com o suprimento de N durante o ciclo da batateira. O objetivo do trabalho foi determinar os valores otimos de indices relacionados com o estado de nitrogenio ao longo do ciclo da batata cultivada em ambiente protegido, utilizando distintos materiais propagativos, tuberculo-semente, minituberculo e broto, comuns na producao de tuberculo-semente basica. Os indices, determinados na quarta folha e na mais velha, foram intensidade da cor verde, avaliada pelo indice SPAD e pela tabela de cor, e caracteristicas agronomicas: comprimento, largura, area e numero de foliolos. Foram realizados tres experimentos em vaso, em casa de vegetacao na Universidade Federal de Vicosa. Em cada experimento, instalado no delineamento de blocos ao acaso, com quatro repeticoes, foram utilizadas seis doses de nitrogenio (0; 25; 50; 100; 200 e 400 mg dm-3). Os indices foram determinados a cada 10 dias iniciando-se aos 20 dias apos a emergencia. Com cada material de propagacao, o indice SPAD medido tanto na QF quanto na FV respondeu de forma diferenciada ao incremento na dose de N e atingiu os valores otimos de 41,3; 40,5; 37,0; 35,8; 36,0; 31,9 e 29,8 dos 20 aos 80 DAE, respectivamente, ao ser utilizado o tuberculo-semente basica. Com todos os materiais de propagacao, a idade da planta influencia significativamente todas as variaveis, exceto o numero de hastes ou o numero de folhas, quando e utilizado broto ou minituberculo, respectivamente. O valor otimo dos indices relacionados com a intensidade da cor das folhas e das caracteristicas agronomicas da planta foram estabelecidos e variam com o material de propagacao e idade da planta de batata.

Uso de hipoclorito de sódio para acelerar a emergência das plântulas e o desenvolvimento das mudas de cafeeiro

The objective of this study was to evaluate the effect of seed imbibition in water solution at different concentrations of sodium hypochlorite on the rate and speed of emergence of coffee seedlings as well as to assess the development of the seedlings. One trial was conducted for each of the five seed moisture content (13%, 18%, 23%, 28% and 33% wet weight). Each one consisted of five treatments, represented by seeds previously imbibed for three hours in water solution with three sodium hypochlorite concentrations (4, 5 and 6% of active chlorine), besides seeds with parchment and seeds without parchment (control). The seedlings were evaluated for the emergence rate and speed, and the seedlings for height, number of leaves and leaf area. The preimbibition of seeds with initial moisture degree of 23, 28 or 33% in water solution with sodium hypochlorite at 4% active chlorine increased the rate and speed of seedling emergence, and improving the seedling development compared to seeds with parchment.