[Mutagenesis and plant phylogenesis]

There are two types of genetic mutations - nuclear and cytoplasmic. We consider genic, chromosomic and genomic nuclear mutations in several seed plant families characterized by different evolutionary age and life forms. "Atlas of chromosome numbers of flowering plants" published in our laboratory in 1969 and containing information about 35 000 species and periodical "Index to plant chromosome numbers" (USA) covering in all about 150 000 species were used for comparative study of chromosome numbers. Gymnosperms originated approximately 300 000 000 years ago and represented predominantly by arboreous and shrub forms are characterized by practically total lack of polyploidy and rare aneuploidy, thus the evolutionary progress in this group has been provided by genic mutations. The morphology of chromosomes in Gymnosperms is much more uniform as compared with Angiosperms - all 200 species of Conifers have 24 large meta- and submetacentric chromosomes Angiosperms. This group originated twice later includes 300 000 species with wide range of living forms - from initial arboreous to ephemeric ones. Therefore, the dominating type of mutations for some groups of Angiosperms as Fagaceae, Aceraceae, Aquifoliaceae, Caricaceae and Lauraceae is genic one. The major part of arboreous Angiosperms has clear polyploid series like 2n = 28, 56, 84 (Betula) and 2n = 38, 76, 114 (Magnolia). Polyploidy is the prevalent type of mutagenesis because of the advantage consisting in amplification of total number of genes against a background of preservation of the genome integrity. The chromosomic type of mutations prevalent in groups with asexual reproduction provides the flow of genes between genomes as a result of aneuploidy. Genomic mutations are observed mostly in herbaceous plants. In such groups as Poaceae, Cyperaceae, Ranunculaceae and Rosaceae we observe up to 90 % of polyploid species. Due to such ploidy restrictions like the size of karyon, and the size and the number of chromosomes numerous shorter polyploid series are observed in this group. Hence primitive mutations are prevalent in ancient Gymnosperms. Chromosomic and genomic mutations arose later providing gene flow without functional changes of source genomes.