Pollen morphology of the Brazilian species of Dyschoriste Nees and Hygrophila R.Br (Ruellieae, Acanthaceae) and its taxonomic significance

Abstract

Acanthaceae is an eurypalinous and pollen morphology has been used in species delimitation and as a support to new taxa recognition. The aim of the present study is to provide new pollen descriptions for the Brazilian species of Dyschoriste (7 spp.) and Hygrophila (4 spp.). We analysed the pollen under light and scanning electronic microscopy. Pollen grains of D. erythrorhiza, D. eulinae, D. glandulifera, D. vinacea, H. acutangula, and H. paraibana are described here for the first time. Dyschoriste species has pollen grains medium to large, isopolar, prolate spheroidal, subprolate to prolate, circular, subcircular, and subtriangular amb, 3-colporate and 13–20-pseudocolpate and the exine is psilate-microechinate to perforate-microechinate. Hygrophila species has pollen grains small to medium, isopolar, oblate spheroidal, subcircular to subquadrangular amb, 4-colporate and 15–21-pseudocolpate and exine is perforate-reticulate. Palynological characters of high taxonomic relevance were: pollen size; pollen shape; length of colpi; endoaperture shape; sexine and nexine thickness; sexine ornamentation; number of pseudocolpi. From our results, a new combination is proposed, D. glandulifera, based on both pollen and macro morphology traits.