Olívia Alvina Oliveira Tonetti

Qualidade física e fisiológica de sementes de Eremanthus erythropappus (DC.) Mac. Leish

This study had the objectives to identify and suggest methods for evaluation of the physical and physiological quality of candeia seeds (Eremanthus erythropappus). The seeds used in the experiments were collected in 2001 and 2002, in the district of Carrancas and Lavras in the State of Minas Gerais. The seeds were dried, cleaned and stored in semi-permeable bags in cold chamber at 5oC and 60% relative humidity until the beginning of the experiments. To make the identification of empty seeds easier, a protocol for x-ray use combining radiation potency (Kv) and time (seconds) of exposition to radiation was developed. To eliminate the empty seeds, an experiment was undertaken using a South Dakota type seed blower combining the opening of the apparatus and time. For the germination tests, seeds were passed through the blower, washed in sodium hypochlorite and placed on paper in gerboxes. The first part was done on a thermogradient table and the second in Mengelsdorfii germinators. The imbibition curves were performed at 30oC at constant light and at 20-30oC and 30-20oC/10 hours under light. The protocol for radiological evaluation that enabled better visualization of the internal structures was 30kv for 45 seconds. The separation of seeds by the blower at the opening 6.0 for the time of 30 seconds allowed an increase from 14.75 to 93.37% in the number of seeds with embryo. The results showed that the seeds did not display dormancy and when the empty seeds were eliminated, the germination percentage was higher. The seeds reached the maximum germination percentage at 14 days of imbibition and the best germination condition was alternate temperature of 20-30oC with 10 hours of light. The germination studies revealed that germination also took place in the absence of light.

Comparação da viabilidade de sementes de Schizolobium parahyba (vell.) blake - leguminosae caesalpinioideae, pelos testes de germinação e tetrazólio

Schizolobium parahyba (Vell.) Blake, conhecido como guapuruvu, pode ser utilizado na construcao civil, na medicina popular e apresenta potencial para uso na recuperacao de matas ciliares. Poucas informacoes sao encontradas na literatura sobre avaliacao da qualidade fisiologica de sementes dessa especie, principalmente em relacao a metodologias para realizacao dos testes de germinacao e tetrazolio. Objetivou-se com este trabalho avaliar a influencia da temperatura no teste de germinacao e da concentracao da solucao no teste de tetrazolio para avaliacao da viabilidade de sementes de S. parahyba. Sementes de dois lotes tiveram seus apices cortados, as quais foram desinfestadas com hipoclorito de sodio e semeadas em bandejas de polietileno (35x20x5cm), sobre areia peneirada, lavada e autoclavada (120oC por 20 minutos). As sementes foram submetidas a temperaturas constantes de 25oC, 30oC, 35oC sob luz continua, e alternada de 20-30oC com 8 horas de luz na temperatura de 30oC. As avaliacoes foram realizadas considerando-se a emergencia de radicula, plântulas normais e indice de velocidade de germinacao. Para o teste de tetrazolio, apos a imersao das sementes em agua por 48 horas, os tegumentos e o endosperma foram removidos e os embrioes imersos nas solucoes de tetrazolio a 0,05% e 0,1% e mantidos em câmara de germinacao tipo BOD no escuro por 5 horas a 30oC. Nos testes de germinacao, as temperaturas de 25oC e 35oC proporcionam maior porcentagem e velocidade de germinacao de sementes de S. parahyba e no teste de tetrazolio, a concentracao 0,05% da solucao permitie avaliar, com eficacia, a qualidade dos lotes de sementes desta especie.

Loss of desiccation tolerance in Copaifera langsdorffii Desf. seeds during germination

This study evaluated the loss of desiccation tolerance in C. langsdorffii seeds during the germination process. Seeds were imbibed for 24, 48, 72, 96, 120 and 144 hours and dried to the initial moisture content, kept in this state for 3 days after which they were submitted to pre-humidification and rehydration. Ultraestructural evaluations were done aiming to observe the cell damage caused by the dry process. Desiccation tolerance was evaluated in terms of the percentage of normal seedlings. Seeds not submitted to the drying process presented 61% of normal seedlings, and after 24 hours of imbibition, followed by drying, the seeds presented the same percentage of survival. However, after 48 hours of imbibition, seeds started to lose the desiccation tolerance. There was twenty six percent of normal seedlings formed from seeds imbibed for 96 hours and later dried and rehydrated. Only 5% of seeds imbibed for 144 hours, dried and rehydrated formed normal seedlings. At 144 hours of imbibition followed the dry process, there was damage into the cell structure, indicating that the seeds were unable to keep the cell structure during the drying process. Copaifera langsdorffii seeds loses the desiccation tolerance at the start of Phase 2 of imbibition.

Swartzia langsdorffii Raddi: morphophysiological traits of a recalcitrant seed dispersed during the dry season

Swartzia langsdorffii seeds have recalcitrant characteristics. Nonetheless, dispersal begins in the month with the lowest precipitation in the studied region, which could lead to seed death by desiccation. Therefore, the objectives of this study were: (1) to characterize the physiological behaviour of S. langsdorffii seeds related to their desiccation sensitivity/tolerance; and (2) to assess the morphophysiological characteristics that enable the seeds to remain viable after dispersal. Fruits and seeds were subjected to biometric evaluation and the anatomical and ultrastructural features of the seeds were determined. Field assessments were performed to determine the capacity of the seeds to maintain viability and to verify the relation between seed viability, diaspore water content and environmental variables. Seeds of this species were found to be recalcitrant and showed pores distributed throughout the seed coat, and contained a large number of stomata in the hypocotyl–radicle axis epidermis. Moreover, phenolic compounds were found throughout the radicle region. Seeds remained viable in the soil for up to 7 months after dispersal without a significant decrease in water content, despite the low precipitation and soil water content. Radicle protrusion began 5 months after dispersal and coincided with partial fruit decomposition at the beginning of the rainy season. Thus, the possible microclimate created by the pericarp, with the moisture content of the aril and the soil, the presence of the structures in the axis, such as the pores and stomata, the chemical composition and the morphology of S. langsdorffii seeds could favour maintenance of their viability until the beginning of the rainy season.

Viabilidade de Sementes de Ocotea puberula (Rich.) Ness ao Longo do Armazenamento

This study aimed to verify the DNA integrity and viability of Ocotea puberula seeds, with and without fruit, during storage. Seeds of five lots were stored, with and without fruit, in cold and dry chamber (40% ± 3% RH; 10 °C ± 2 °C) for 0, 3, 6, and 9 months. The following attributes were determined at each period: water content, germination potential (%), tetrazolium (%), and DNA integrity. Seed germination was conducted in germitest paper, in germinator at 30 °C under constant light. The tetrazolium test was performed in 0.5% solution for 1 hour. The DNA integrity of seeds was analyzed in agarose gel and DNA concentration was measured using a NanoDrop® spectrometer. The results showed that only seeds without fruit maintained germination for three months; after this period, the germination of seeds reduced gradually, becoming null after nine months. Seed degradation during storage was observed in the DNA integrity analysis. Ocotea puberula seeds, with or without fruit, stored in Kraft paper bags in cold and dry chamber had their viability and DNA integrity reduced after three months.

Utilização do teste de raios - x na avaliação dos efeitos da dessecação e infestação em diásporos de Canela-Batalha - Cryptocarya aschersoniana Mez (Lauraceae)

No presente trabalho, objetivou-se avaliar os efeitos da dessecacao e identificar lesoes por predacao por insetos, em diasporos de canela-batalha (Cryptocarya aschersoniana Mez.), utilizando-se testes de raios X. Os danos provocados pela dessecacao foram dimensionados nas imagens e associados a formacao de plântulas. Diasporos recem-beneficiados (45 % de umidade e 37 % de germinacao) foram colocados para secar em sala climatizada (20 oC e 60 % UR), dentro de bandejas plasticas em camada unica. Posteriormente, com o intuito de acelerar o processo de secagem, foram colocados em caixas de secagem com solucao saturada de hidroxido de sodio (28 % UR) e amostrados com 45, 37, 35, 31 e 26 % de umidade. Para as radiografias, utilizou-se a intensidade de radiacao de 40 kVp e tempo de exposicao de 1,5 minutos. Posteriormente, as radiografias foram fotografadas e as imagens analisadas em computador, sendo medido o afastamento entre o endocarpo e a semente. As sementes foram classificadas em sementes intactas, sementes com afastamento parcial, sementes com afastamento total e sementes predadas. Os testes de germinacao foram realizados sobre areia, em germinadores tipo Mangelsdorf a 25 oC e luz branca constante. Pelos resultados, observa-se que a germinacao e comprometida quando o teor de agua das sementes fica abaixo de 26 %. Nesse ponto, o afastamento entre o endocarpo e a semente e de 0,65 mm. Houve uma correlacao positiva entre a viabilidade das sementes, avaliada pelo teste de germinacao, e o afastamento entre o endocarpo e a semente observado nas radiografias. A analise radiografica possibilita identificar danos provocados por predacao apos infestacao por insetos.

Armazenamento de sementes de Alfavaca-cravo (Ocimum gratissimum L.)

The Ocimum gratissimum L. species is an aromatic subshrub that belongs to the Lamiaceae family and is considered as an important producer of essential oil, widely used in folk medicine. Because of the lack of information about the conservation of O. gratissimum seeds, we aimed to evaluate the longevity of the seeds on different storage conditions for 12 months through the germination and seedling formation percentage in this study. The seeds were stored in three types of packages: paper bags (permeable), aluminized paper bags (semipermeable) and glass flasks (impermeable), in the settings of laboratory bench, refrigerator and cold room over the 12 month period. The germination tests were performed on the 6th, 8th, 10th and 12th month, when moisture, germinability, germination velocity index and percentage of normal seedlings were evaluated. During the storage period, moisture, germinability and percentage of normal seedling were kept in each storage condition. The stored seeds showed increased values of GSI compared to the newly- harvested ones.