Comparative study of the karyotypes of South American species of Araucaria

Root tips of both Araucaria araucana (Mol.) Koch and Araucaria angustifolia (Bert.) O. Ktze. were used as sources of mitotic chromosomes. Both species have 26 chromosomes as the diploid number, consisting of 13 pairs of homologues. In both species 10 pairs of chromosomes are metacentric, and 3 pairs are submetacentric with slight differences in the centromere position between the two Araucarla species. Both karyotypes also are characterized by a metacentric pair of chromosomes having a long inter calar constriction close to the centromeric region. Amrnoniacal silver staining identifies this long constriction as the nucleolus organizer region or NOR. In addition, one of the metacentric pairs of A. angustifolia chromosomes has a small terminal satellite. © 1984, American Genetic Association.