Solange Carvalho Barrios Roveri José

Armazenamento de sementes de girassol em temperaturas subzero: aspectos fisiológicos e bioquímicos

The significant progress in Brazilian agricultural production has been due its capacity to incorporate and use genetic resources. Embrapa Genetic Resources and Biotechnology is the institution responsible for the long-term conservation of the seed germplasm of many crops, stored at -20 °C. Appropriate storage is necessary for correct germplasm management, to ensure the quality of the material stored and minimize the deterioration process. The objectives of this study were to evaluate the effect of seed water content on the tolerance to storage at sub-zero temperatures of -20 °C and -196 oC, to associate the tolerance level with physiological and biochemical aspects and to verify the effect of the pre-humidification of seeds on physiological quality after storage. Seed quality was evaluated by tests of electrical conductivity, first and final count of germination and determination of the peroxide index. Sunflower seeds can be dried to 3.2% of water content in silica gel or in a drying chamber and stored at -20 °C or -196 °C without loss of germination and vigor. Seed deterioration, evaluated by the peroxide index, was lower in seeds stored in NL. The humidification treatment was important for the evaluation of seedlings in the first count of germination test and the electrical conductivity test.

Aspectos químicos e estruturais da qualidade fisiológica de sementes de soja

The objective of this work was to evaluate the additive and non-additive genetic effects for thickness of the seed coat layers and of the lignin present in them, and to verify if the characters used to evaluate the physiological quality of the seeds is correlated with the lignin content. Three cultivars (M-Soy 8400, CD201, CD206) with high and three (CD215, CD202, Savana) with low physiological quality were used to obtain F1 and F2 hybrid seeds, including the reciprocals, using partial diallel crosses and the parental lines. First germination count, final germination count and germination rate, used to evaluate the physiological quality, can be correlated with lignin content. Positive correlations were observed between lignin content and the percentage of normal seedlings in the aging test at the 5th and 11th days after sowing, with the highest correlation values at the 5th day. The correlation between germination rate and lignin content was negative. The diallel analysis showed reciprocal effect, showing that the thickness of the seed coat layers and of the lignin contained in these layers can be explained by maternal effect.

Tolerância de sementes de linhagens de milho à alta temperatura de secagem

Cultivares tolerantes a altas temperaturas de secagem proporcionam reducao no tempo de secagem, uma etapa critica no sistema de producao de sementes de milho (Zea mays L.). Nesta pesquisa, foi avaliada a tolerância a alta temperatura de secagem de sementes de linhagens de milho, por meio de testes de germinacao e vigor. As sementes foram colhidas manualmente em espigas com teor de agua em torno de 35% e secas artificialmente a 45 C ate atingirem 11% de teor de agua. Em seguida, foram submetidas aos testes de primeira contagem e contagem final de germinacao, envelhecimento acelerado, teste de frio sem solo e de condutividade eletrica. Houve diferencas significativas nos valores de germinacao e vigor de sementes das diferentes linhagens, sendo entao classificadas em tolerantes e intolerantes. Pelos resultados, conclui-se que a sensibilidade das sementes a injuria por secagem a alta temperatura e dependente da linhagem.