Pollen morphology in the genus Dyckia (Bromeliaceae): endemic species from southern Brazil comprising the proposed infrageneric grouping “D. selloa complex”

Abstract

Dyckia, belonging to the Bromeliaceae, consists of species that share several morphological similarities. Recently, a proposal has grouped 13 species of the genus into a “D. selloa complex” based on their limited geographical distribution and seed characteristics. However, further investigation is required to gain a better understanding of this grouping. This study aimed to analyze the pollen grain morphology of the grouped species. The analysis was conducted using scanning electron microscopy (SEM), as well as light microscopy equipped with bright field and fluorescence optics. Various structures were measured. The pollen grains are heteropolar, oblate, and range in size from small to medium. They possess a simple sulcus type and exhibit a sexine (composed of tectum and infratectum columellate) and a nexine 1. Different patterns of ornamentation were identified, including reticulate, microreticulate, reticulate with free granules, reticulate with a partially discontinuous reticulum, and reticulate with a discontinuous reticulum. The aperture margin of some species differs from the described characteristics for the genus (Puya type) and is referred to here as the “Other” type. The results align with existing data for the genus Dyckia and contribute to understanding the pollen morphology within the genus and the studied group. The data obtained in this study, along with the observed variations, could facilitate a better understanding of the “D. selloa complex”.