Alismatales sensu stricto : análise citogenética com técnica convencional, bandeamento e sítios de DNAr 45S

Abstract

The order Alismatales corresponds to one of the basal monocotiledones clads and is found predominantly in habitats aquatic or semiaquatic. The present work aimed to understand the internal taxonomic relations and the karyotype evolution in a monofiletic group of Alismatales of exclusively neotropical occurrence. Five species of Alismataceae and four of Limnocharitaceae were investigated using 2% Giemsa, silver nitrate staining, C-banding, CMA/DAPI fluorochromes staining and fluorescence in situ hybridization (FISH) with probes of ribossomal 45S DNA. One species of Hydrocharitaceae was also staining with Giemsa 2%. In Alismataceae, the Echinodorus species showed 2n=22 and CMA/DAPI and C/CMA/DAPI bands located in the short arm and satellite of two of the smallest acrocentric chromosomes pairs. Fluorescence in situ hybridization with 45S rDNA probe co-localized in general, with the blocks revealed after fluorochromes staining, with exception of E. andrieuxii, for which only three 45S rDNA sites were detected. E. lanceolatus was the only species with DAPI+ bands, which were located in the telomeric regions of seven acrocentric pairs. In Limnocharitaceae, Hydrocleys (2n=16) and Limnocharis (2n=20), the CMA+ regions had corresponded to the RONs and the 45S rDNA sites in Hydrocleys nymphoides and Limnocharis flava. L. laforestiidiffered in relation to the number of 45S rDNA because two sites were observed in the later. In Hydrocleys nymphoides and H. martii the GC-rich in the heterochromatin was associated with the satellite located in the smallest acrocentric pair, and in a metacentric pair of intermediate size in the later. The only representative of Hydrocharitaceae, Limnobium laevigatum showed 2n=28 and an asymmetric bimodal karyotype as well as the other investigated species. In the group examined the refined techniques cytogenetic provided information such as detection of structural chromosome changes important for the karyotype evolution in Alismatales.