Caracterização palinológica, citogenética e morfológica de espécies do gênero Calliandra Benth. (Leguminosae - subfamília Caesalpinioideae e Clado Mimosoid) ocorrentes no nordeste do Brasil

Abstract

Calliandra Benth. is a neotropical genus with 139 species and distributed in three main regions of the American continent. One of these regions is northeastern Brazil, considered one of the centers of diversity of the genus, with 66 species; among these twenty-six are representatives of the Androcallis section, four of the Microcallis section and thirty-six of the Monticola section, occurring in areas of vegetation formation caatinga, cerrado and ecotones. The present study aimed to analyze pollinic units of Calliandra species in the Androcallis Barneby section, Microcallis Barneby section and Monticola ER Souza and LP Queiroz section, occurring in northeastern Brazil, and to provide comparative cytogenetic analyzes regarding chromosome number, ploidy level and distribution of heterochromatic regions AT and CG in ten species of Calliandra belonging to the Androcallis section, using the CMA/DAPI technique, in addition to conducting a taxonomic study of species occurring in the state of Piauí. Expeditions were carried out to collect botanical material in several states in the Northeast for taxonomic, palynological and cytogenetic studies. Comparative palynological and cytogenetic analyzes were carried out to differentiate the species studied using the acetolysis technique to determine the patterns of pollen dispersion units (polyads) and chromosomal banding with chromomycin A3 fluorochromes (CMA), for rich chromosomal regions in base pairs guanine and cytosine and 4',6-diamidino-2-phenylindol (DAPI), for localization of the regions rich in adenine and thymine base pairs. Flow Cytometry technique was also used to measure the DNA content of the species studied. The results observed in the palynological analyzes allowed to characterize and group different species, mainly those belonging to the Monticola section in relation to their respective characteristics and dimensions of their polyads. The data collected increases the number of information for species not yet studied and corrects dubious questions in relation to the number of grains per polyad of some species of the genus. Diploid species (2n = 2x = 16) were found C. macrocalyx, C. riparia, C. imperialis, C. ulei, C.spinosa and C. umbellifera; tetraploid species (2n = 4x = 32) C. fernandesii; octoploid species (2n = 8x = 64) C. sessilis and decaploid species (2n = 10x = 80) C. dysantha, confirming the proposal for the basic number of the genus of x = 8, characterized in their different ploidy levels. The results found for the DNA content confirm what is proposed for the differences in chromosomal size and ploidy observed in the species under study. Among the analyzed species, the event of disploidy was not observed. The use of double CMA/DAPI staining revealed band patterns that allowed to identify and differentiate each species. As for the number of CMA+ signals, it was possible to differentiate three groups, one with 6, another with 8 and another with 10 bands for the Androcallis section, suggesting that chromosomal rearrangements and polyploidy have contributed to the evolution of the species evaluated. The use of the cytogenetic technique with CMA/DAPI fluorochromes enables the characterization and differentiation in cytotaxonomic studies for this genus. The observed morphological data contribute to the taxonomy of the genus and to a better knowledge in the distribution of the different taxa found in the state of Piauí, Brazil.