Cytogenetics of Alismatales s.s.: chromosomal evolution and C-banding

Ten species of Alismatales, five of Alismataceae, four of Limnocharitaceae and one of Hydrocharitaceae were studied with regard to chromosome number, chromosome morphology, and pattern of Giemsa C-bands. The genus Echinodorus had a diploid chromosome number of 22 for all species that were analyzed and a karyotypic formula of 2m + 20a. For the family Limnocharitaceae, Hydrocleys nymphoides had a diploid chromosome number of 16, Hydrocleys martii (4m + 2sm + 10a) had a diploid chromosome number of 16, Limnocharis flava had a diploid chromosome number of 20 and L. laforestii (4m + 16a) had a diploid chromosome number of 20. The only species of Hydrocharitaceae that was studied exhibited a karyotype that consisted of a diploid chromosome number of 28 and a karyotypic formula of 4m + 6sm + 4a. The distribution pattern of the C-banded karyotype in Echinodorus showed four blocks of constitutive heterochromatin in two smaller acrocentric pairs that corresponded to the heterochromatic NORs. In E. lanceolatus, 14 bands in the termini of the arms beyond the heterochromatic NORs of seven acrocentric pairs were also observed. Idiograms are presented and the karyotypic evolution patterns for the studied groups are discussed.