Cambial patterns of Paullinia (Sapindaceae) in southwestern Amazonia, Brazil

Paullinia comprises 220 species. In Brazil, there are 99 species of the genus distributed mainly in Amazonian forest and the Atlantic Forest, where there are 73 and 26 species, respectively. Until now, the stem anatomy of only 13 species of Paullinia has been investigated. Given the importance of information on cambial variants to the taxonomy of Sapindaceae, studies on the stem anatomy of species in the family are very relevant. The present study described the stem diversity of ten species of Paullinia, which were collected in areas difficult to access in Amazonian forest, in the state of Acre. Micro- and macroscopic analyses were carried out. Two types of cambial variants were identified: lobed stem and xylem interrupted by phloem wedges. The latter type was recorded for the first time in the genus. The anatomical study recorded different traits that might be useful for distinguishing taxa, including morphologically similar species, such as P. bracteosa and P. imberbes and P. fimbriata and P. rugosa. We believe that the results enrich the taxonomic descriptions of the analyzed species and will provide data for future evolutionary studies of the group.