Cell cycle activity and beta-tubulin accumulation during dormancy breaking of Acer platanoides L. seeds

Cell cycle events in embryo axes of Norway maple (Acer platanoides L.) seeds were studied during dormancy breaking by flow cytometric analyses of the nuclear DNA content and by immunodetection of beta-tubulin. Most embryonic nuclei of dry, fully matured seeds were arrested in the G(2) phase of the cell cycle. In addition, the lowest content of beta-tubulin was detected in dry, mature seeds. Imbibition in water and cold stratification resulted in a decrease in the number of nuclei in G(2), and a simultaneous increase in beta-tubulin content. In germinated seeds the content of beta-tubulin was the highest and the number of cells in G(2) was the lowest. Both cell cycle events preceded cell expansion and division and subsequent growth of the radicle through the seed coat. The anatomical investigation has proved that the main reason for decrease in the number of nuclei in G(2) is mitosis, started with seeds germination ( radicle protrusion). The activation of the cell cycle and the beta-tubulin accumulation were associated with embryo dormancy breaking.