MARCHANTIA POLYMORPHA L. S. LAT. KARYOTYPE ANALYSIS

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  No significant interpopulation variation in chromosome size or the location of centromeres and constitutive heterochromatin could be found in Marchantia polymorpha s. lat. The karyotype of M. polymorpha L. s. lat, as well as of M. plicata Nees et Mont. and M. berteroana Lehm. et Lindenb. comprises six metacentric, two submetacentric and one m-chromosome. The m-chromosome differs in size and structure in male and female plants. The only other difference found among the populations examined is in the location of the nucleolar organizer, which is on a small metacentric chromosome in all except a Japanese specimen where it occurs on the m-chromosome. Speciation in Marchantia subg. Marchantia seems not to have involved major chromosome rearrangements. Constitutive heterochromatin, as defined by Giemsa C-banding, is present in small quantities but does not provide enough cytological markers by which to assess the hybrid status of M. polymorpha s. str., or the distinctions between M. polymorpha s. str., M. aquatica (Nees) Burgeff and M. alpestris (Nees) Burgeff.