Pollen morphology and wall structure of Neotropical species of Herreria and Clara (Asparagaceae-Agavoideae) and its taxonomic implications.

Pollen morphology and wall structure of Clara and Herreria were investigated in order to clarify their taxonomy. Materials treated with a lactic acetolysis method at 40 % were used to obtain measurements, descriptions, and illustrations using light microscopy. Non-acetolyzed pollen grains were analyzed with scanning electron microscopy to characterize the surface details and apertures. As a result of this work, an identification key was prepared for Clara and Herreria species based on pollen morphology. All species present medium-sized pollen that are also heteropolar, elliptic amb, and monocolpate, with perforate, microreticulate, or reticulate surfaces. The two species of Clara differ with regard to their colpus dimensions and sexine ornamentation, and the seven species of Herreria can be distinguished by their sexine ornamentation, confidence interval values for the largest diameters, and colpi width. It was concluded that pollen morphology proved to be uninformative for differentiating the genera Clara and Herreria, but useful for distinguishing between related species. [ABSTRACT FROM AUTHOR]