Denise Cunha Fernandes dos Santos Dias

Teste de envelhecimento acelerado em sementes de pimenta

The objective of this study was to adequate the methodology of accelerated aging test for vigor evaluation of pepper seeds. Six seed lots of pepper were tested for germination, germination at first count, cool germination and accelerated aging. For accelerated aging, the following methods were tested: traditional (100% RH) and modified (76% RH), at 38, 42 and 45oC for 48, 72 and 96 hours. The accelerated aging test was efficient for vigor evaluation of pepper seeds producing results similar to the first count and cool germination test, especially when conducted at 38 or 42oC for 96 hours by both traditional and modified methods.

Uso do teste de tetrazólio para avaliação da qualidade fisiológica de sementes de abobrinha

165RESUMO – O trabalho teve como objetivo desenvolver metodologia apropriada para o uso doteste de tetrazolio em sementes de abobrinha, visando determinar a viabilidade e o vigor. Osseguintes procedimentos foram avaliados: umedecimento das sementes em papel toalha por 16 e24h, a 25°C; imersao direta em agua, em câmara BOD, a 40°C, por 15, 30 e 60 minutos para a remocaodo tegumento e por mais 30 e 60 minutos para retirada da membrana que envolve o embriao. Osembrioes foram entao imersos em solucao de tetrazolio a 0,05 e 0,075% por 30, 60 e 90 minutos, emcâmara BOD, a 40°C, para coloracao. Paralelamente, foram conduzidos testes de germinacao evigor, estabelecendo-se cinco classes de viabilidade e vigor. A metodologia desenvolvida foiaplicada a oito lotes, sendo aferida com os resultados dos testes de germinacao, envelhecimentoacelerado e emergencia de plântulas em areia. O teste de tetrazolio mostrou-se eficiente para avaliara viabilidade e o vigor das sementes de abobrinha. O metodo de pre-condicionamento mais eficientefoi imersao direta em agua, a 40°C, por 30 minutos para a remocao do tegumento e por mais 30minutos para a retirada da membrana interna. A coloracao ideal dos embrioes foi obtida apos 60minutos de imersao em solucao de tetrazolio a 0,05 ou 0,075% a 40°C.Termos para indexacao:

Primed carrot seeds performance under water and temperature stress

Uniformity and percentage of seedling emergence of direct-seeded vegetables have a major impact on their yield and quality. Depending on temperature and soil water potential, carrot seeds performance in the field is poor justifying the use of techniques to accelerate the germination and seedling emergence. The objective of this work was to evaluate the effects of priming treatments, with and without aeration, on carrot seeds performance under water and temperature stress. Two seed lots of carrots, Brasilia cultivar, were primed in PEG 6000 -1.0 and -1.2 MPa solutions, for four and eight days, at 20oC, using two imbibition methods: priming in paper towel moistened with the respective solutions and immersion into aerated osmotic solutions. Non-primed seeds were used as control. After priming, the seeds were dried at room temperature until reach initial seed moisture content. The seeds were submitted to the following tests: germination, first count, seedling emergence in the field, germination at sub-optimal (15oC) and supra-optimal temperature (30oC) and germination under water stress (PEG 6000 at -0.4 MPa). Priming in -1.0 and -1.2 MPa PEG 6000 during four and eight days can be useful for improving carrot seedling emergence in the field and seed performance under supra and sub-optimal temperatures. Aeration of the peg solution was beneficial when seeds were primed at -1.2 MPa for eight days.

Germination and vigour of primed asparagus seeds

The osmotic conditioning or priming is considered a promising technique to speed up germination and to improve seed performance. Four seed lots of asparagus, Mary Washington cultivar, were primed at 25°C for seven or 14 days using PEG 6000 at -1.0 or -1.2 MPa, or sea water at -3.3 MPa; or for three days in distilled water. The physiological quality of the seeds was evaluated by standard germination, first count germination, speed of seedling emergence, and germination percentage and seedling fresh and dry weights after controlled deterioration test. Primed seeds presented higher germination speed, independently of their initial physiological quality. Beneficial effects of priming on germination and vigour were more expressive in the seed lot of low physiological quality. Priming in PEG 6000 at -1.0 MPa for 14 days was the most beneficial treatment to improve asparagus seeds performance.

Changes in seed quality during fruit maturation of sweet pepper

Studies regarding seed maturation are important to determine the ideal fruit development stage for harvesting in order to obtain high-quality seeds. Changes in sweet pepper (Capsicum annuum L.) seed quality were monitored during seed development in order to identify the stage of maximum quality of the seeds and the optimum harvest date. Fruits harvested from 20 to 75 days after anthesis (DAA) with step of five days were grouped according to maturity stage (green, yellow, red and intense red color outside). Before seed extraction, the fruit weigh, diameter and length were determined. Seed water content, seed dry weight, 1.000-seed weight, germination, first count, speed emergence index, seedling length, accelerated aging and electrical conductivity tests were performed. Mass maturity of the seeds was attained at 75 DAA, when seed water content was 47.3 % and the fruits were red. Sweet pepper seeds with high germination and vigour should be harvested when fruits are completely red outside, at 75 DAA.

Comparação entre testes de vigor para avaliação da qualidade fisiológica de sementes de tomate

The objective of this study was to compare different methods for vigour evaluation of tomato seeds. Four seed lots of the Santa Clara cultivar were evaluated by the following tests: standard germination, first count of germination test, cool germination, accelerated aging, controlled deterioration and seedling emergence in soil. It was concluded that the accelerated aging and the first count of germination tests were not efficient in detecting differences among vigour levels of seed lots seed lot vigor levels. The cool germination and seedling emergence in soil tests identified seed lots of with high and low vigour levels. Similar classification in vigour levels were was obtained by the controlled deterioration test conducted at 41oC for 48h and 24% seed moisture content.

Pre-germinative treatments in castor bean (Ricinus communis L.) seeds

Castor bean seeds have slow and irregular germination that frequently results in irregular seedling emergence in the field. This fact has been attributed to their probable impermeability to water. The objective of this study was to evaluate the effect of pre-germination treatments on seed performance. Five seed lots, AL-Guarany cultivar, were submitted to the following treatments: control (untreated seeds), scarification with sandpaper, caruncle removal, tegument removal, immersion in water for 12 and 24h, caruncle removal + immersion in water for 12 and 24h, scarification with sandpaper + immersion in water for 12 and 24h, germination at 10oC/7 days and at 25oC/5 days, germination at 10oC/7 days and at 30oC/5 days, accelerated aging at 41oC/48h and 100% RH. After each treatment, with exception of the germination at 10oC, the seeds were submitted to the germination test, at 25oC. Counts were performed at 7 and 14 days after sowing. In general, all the pre-germination treatments contributed to increasing the germination percentage of castor bean seeds in relation to the control. The most efficient treatments to speed up germination were scarification with sandpaper and caruncle or tegument removal. However, considering the practical application, scarification can be recommended to increase the percentage and speed of seed germination.

Controle da hidratação para o condicionamento osmótico de sementes de aspargo

RESUMO - Como o aspargo apresenta a germinacao da semente e a emergencia da plântula lentas, justifica-se o uso de tecnicas que acelerem a germinacao, como o condicionamento osmotico das sementes. Inicialmente, para definir as melhores condicoes de condicionamento das sementes, e necessario conhecer os padroes de embebicao dessas sementes para se ter um controle adequado da hidratacao. Assim, este trabalho teve como objetivo conhecer o padrao de embebicao das sementes de aspargo com vistas ao seu condicionamento osmotico. Utilizaram-se quatro lotes de sementes de aspargo, cultivar Mary Washington, determinando-se as curvas de embebicao das sementes, para cada lote, em agua destilada, em PEG 6000 a –1,0MPa e –1,2MPa e em agua do mar a –3,3MPa, em BOD a 25 0 C. Para tanto, determinou-se o grau de umidade das sementes apos 2, 4, 6, 8, 10, 12, 24, 48, 72, 96, 120, 144, 168, 336, 504 e 672 horas de embebicao em PEG 6000 a –1,0MPa e –1,2MPa e em agua do mar a –3,3MPa. Para o condicionamento em agua destilada, o grau de umidade das sementes foi determinado apos 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 24, 48, 72, 96, 120, 144 e 168 horas de embebicao. Para a determinacao do grau de umidade, adotou-se o metodo da estufa a 130 0 C/1 hora. Verificou-se que em agua destilada houve rapida hidratacao das sementes, com a protrusao da raiz primaria a partir das 120 horas (5 o dia) de embebicao. No condicionamento em PEG 6000 a -1,0MPa, a partir das 504 horas (21 dias) de embebicao, houve lento incremento no grau de umidade das sementes, iniciando-se a protrusao da raiz primaria. Um controle eficiente da hidratacao foi obtido nas sementes embebidas em PEG 6000 a -1,2MPa e em agua do mar a -3,3MPa, onde nao ocorreu protrusao da raiz primaria ate 672 horas (28 dias) de embebicao.

Dinâmica de reservas das sementes de soja durante o desenvolvimento de plântulas de diferentes cultivares comerciais

Physiological quality and vigor of the seeds comprise properties that determine a high level of activity and performance during germination and seedling emergence, having a direct relation with the establishment of the stand of a crop. In this context, the assessment of seedling development, including the analysis of the seed reserves mobilization are a reliable method to investigate the physiological potential of seed lots. In this preliminary study, the aim was to investigate the dynamics of seed reserves mobilization of a sample of soybean commercial cultivars. By means of the seedling length bioassay and weight of dry matter of seeds, cotyledons, hypocotyls and radicles, information on the reserves mobilization during the germination process was obtained. Data were subjected to analysis of variance and Scott and Knott test, and afterwards, phenotypic correlations between traits were obtained. The results have shown that the dry matter of seeds, reserves reduction of seeds and dry matter of seedlings are positively correlated, and thus, seeds containing more reserves may be more effective during the early development of seedlings. In contrast, reserve reduction of seeds and conversion efficiency of the seeds reserves in the dry matter of seedlings are negatively correlated.

Testes fisiológicos e bioquímicos na estimativa do potencial de armazenamento de sementes de algodão

A pesquisa teve por objetivo avaliar a eficiencia de testes de vigor e de determinacoes bioquimicas em estimar o potencial de conservacao de sementes de algodao (Gossypium hirsutum L.) durante o armazenamento por doze meses, em câmara fria e em condicoes de ambiente no Setor de Armazenamento do Departamento de Fitotecnia da UFV. Antes do armazenamento, as sementes foram submetidas aos seguintes testes e determinacoes: germinacao, envelhecimento acelerado, germinacao a baixa temperatura, emergencia das plântulas em leito de areia, condutividade eletrica, teor de lipidios e atividades de lipoxigenase, fosfatase acida e inibidor de tripsina. Para estimar o potencial de armazenamento, aplicou-se uma analise das distâncias generalizadas de Mahalanobis entre os resultados obtidos nos testes de vigor e nas determinacoes bioquimicas realizadas antes do armazenamento e os percentuais de germinacao obtidos a cada dois meses de armazenamento. Os testes de envelhecimento acelerado e de germinacao a baixa temperatura, realizados antes do armazenamento, podem ser utilizados para estimar a viabilidade das sementes, respectivamente, apos oito e dez meses de armazenamento em ambiente. O teste de condutividade eletrica e as determinacoes bioquimicas nao permitem prever o potencial de armazenamento das sementes de algodao.