Cytogenetics of Rutaceae IV

Structure and systematic significance of interphase nuclei

Abstract

The interphase nuclei of 68 species of Rutaceae representing the eight major tribes in the family were analyzed. Nuclei were classified as areticulate (two types), semi-reticulate (five types) and reticulate (one type). No eureticulate nuclei were detected. Variation of the structure among different tissues, individuals or species of the same genus was minimal and mainly associated to tissue differentiation or ploidy levels. The differences in chromatin organization among nuclear types are mainly correlated with the pattern of prophase condensation and the amount of nuclear DNA. The structure of the interphase nucleus appears to be particularly important in the cytogenetical characterization of tribes and sub-tribes of the Rutaceae. The tribe Aurantieae is the only one to be characterized by a single nuclear type (areticulate) whereas the remaining tribes show varied nuclear structure for the different subtribes. Some tribes, as Rutineae and Cusparieae, appear to have a characteristic nuclear type for each subtribe. The systematic significance of these findings is discussed.