Perda da tolerância à dessecação em sementes de Copaifera langsdorffii Desf. de diferentes ambientes

Abstract

One of the seed characteristics that represent a challenge for those who propose to work with conservation is the desiccation sensitivity. This characteristic is found in a large number of species of agronomic, forest and medicinal interest. Orthodox seeds in germination process have been used in studies regarding this theme. In general, orthodox seeds present loss of desiccation tolerance after radicle protrusion, however, Copaifera langsdorffii seeds lose such capacity precociously, becoming sensitive in phase 2 of imbibition. Therefore, considering the need for studies related to the effect of the maternal environment over the desiccation tolerance, the present work aimed at analyzing molecular and ecological aspects of the loss of desiccation tolerance in C. langsdorffii seeds in germination process. The seeds were collected from areas of Stricto Sensu Cerrado in Montes Claros and Lavras, MG, Brazil, as well as in areas of riparian forest in Lavras, MG. The seeds from all three origins presented precocious loss of desiccation tolerance, however, seeds from Montes Claros maintained desiccation tolerance for a longer period then the remaining origins. Seeds from the Cerrado of Montes Claros were used in the biochemical and molecular analyses. Greater changes were observed in oligosaccharides of the raffinose family (raffinose, stachyose and trehalose), over the soaking process, being absent in stages desiccation sensitive. Genes related to germination had their expression increased during germination while those related to tolerance to desiccation decreased, increasing again after the treatment of reestablishment desiccation tolerance. It was possible to conclude that there is influence of the maternal environment over the loss of tolerance to desiccation in C. langsdorffii seeds and that the concentrations of oligosaccharides of the raffinose family, the synthesis of proteins resistant to heat and the expression of the genes superoxide dismutase, ABA1 and heat resistant proteins is correlated with the loss and reestablishment of desiccation tolerance of seeds from this species.