Abstract

Mitotic metaphase plates were analyzed in Eucalyptus globulus Labill. and Eucalyptus cladocalyx F. Muell. The chromosomes were observed by squashing root tips, pre-treated with 8-Hydroxyquinoline and stained with the Feulgen reaction. Both, E. globulus and E. cladocalyx had a karyotype of 2n = 22, with 1A symmetry level, and chromosome sizes varying between 0.68 and 2.03 m m. Mean chromosome size differed significantly between E. cladocalyx (1.42 m m) and E. globulus (1.02 m m) (P < 0.01). The greater chromosomal size of E. globulus suggests a greater amount of DNA, probably originated by structural alterations. This evolutionary pattern of karyotype morphology might be associated, as well, with a high level of conservation in chromosome morphology.