Protocolo de crioconservação de sementes de algodão (Gossypium hirsutum L.raça latifolium Hutch.) cultivares BRS 200 Marrom r BRS Verde

• Autor(a) principal: Coelho, Robson Rogerio Pessoa
• Data de Publicação: 2006
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFPB
• Texto Completo: https://repositorio.ufpb.br/jspui/handle/tede/8139
• topic: Sementes de algodão; Cotton seeds; Temperaturas subzero; Nitrogênio líquido; Subzero temperatures; Liquid nitrogen; CIENCIAS AGRARIAS::AGRONOMIA

The preservation of seeds of economical value in liquid nitrogen or cryoconservation has the potential of extending the storage period almost indefinitely. However, during the freezing and thawing processes, the reached temperature can cause stress that could be lethal for many biological material species, including seeds. The capacity of seeds to resist to freezing in liquid nitrogen is configured as critical factor for the long term conservation. In this work and attempt was made to investigate the cryoconservation of herbaceous color cotton seeds from the cultivates BRS 200 Brown and BRS Green, material developed by Embrapa Algodão. In this case, the study was divided in four parts in the attempt to include all the stages for the establishment of a long term storage protocol in cryogenic temperatures. It was studied the determination of the high moisture freezing limit for the cryoconservation, the kinetics of cryogenic freezing in different temperatures, the storage in subzero temperatures for 12 months (cryoconservation), and, finally, the possible degradation of essential chemical substances to the germination process, considering the exposition of seeds to such extreme storage conditions. The high moisture freezing limit of cotton seeds from the two cultivates range from between 6-8%, while for the long term storage there was a drop in germination and vigor in the two cultivates in any of the temperatures and thawing methods used. It was verified that the freezing curves of these seeds mainly in the temperatures of -25, -45 and -170oC, in spite of the largest similarity with the cooling curves, they present, although in discrete way, the three characteristic phases of the curve of freezing of the pure water. With regard to the thermal diffusivity, it was concluded that it increases with the increase in humidity content, and it does not present a symmetrical behavior with temperature oscillation. The found results also allow to conclude that the seeds of the two cultivates have similar chemical composition and that, in general, there was a decrease in the reserve of chemical components during storage, except for the minerals.