Avaliação da perda da tolerância à dessecação e da quantidade de dna nuclear em sementes de Peltophorum dubium (spreng.) taubert durante e após a germinação

Abstract

The objective of this study was to investigate the loss of desiccation tolerance (DT) in seeds of Peltophorum dubium (Sprengel) Taubert, during and after germination. P. dubium seeds were sown, removed after germination when the primary root lengths reached 1, 3 and 5 mm (68% water content), dehydrated in silica gel until they had reached their initial moisture content (8%), rehydrated and evaluated for survival (resumption of growth and development of normal seedlings). This procedure was also followed in the assays during imbibition, where 4 replications of 25 seeds were subjected to 12, 24, 48, 60 and 72 hours of imbibition. Subsequently, different points were selected (12, 48 and 60 hours of imbibition and radicles 1 mm long) to evaluate the nuclear DNA content in order to relate the beginning of the cell cycle with the loss of DT. For the three radicle lengths sampled, there was no survival of seeds which had been dried and rehydrated. There was a progressive decrease in the survival of P.dubium seeds related to the imbibition period and subsequent drying and rehydration, suggesting that the loss of DT occurs early in germination before radicle protrusion. Seeds imbibed for 12, 24, 48, 60, 72 hours and germinated seeds with 1 mm long radicles showed 98%, 93%, 83%, 35%, 17% and 0% survival, respectively. The assays with the nuclear DNA content do not show any relationship between the resumption of the cell cycle and the loss of DT.