Palynological study of species of Bromeliaceae belonging to subfamilies with restricted occurrence (Brocchinioideae, Hechtioideae, Lindmanioideae, Navioideae, and Puyoideae)

Bromeliaceae comprises eight monophyletic subfamilies. Five of these subfamilies (Brocchinioideae, Hechtioideae, Lindmanioideae, Navioideae, and Puyoideae) have been recently established and exhibit restricted geographic distribution, which hinders the sampling of plant material. Consequently, few studies have provided palynological descriptions of species within these subfamilies. This study aimed to describe the pollen grains of species belonging to these five subfamilies and integrate the results with existing palynological information available in the literature. Acetolysis and scanning electron microscopy were used for pollen analysis. Pollen grains of the five subfamilies are monads, heteropolar, and bilaterally symmetric, with variations in shape and amb. Pollen grains of Puyoideae are large, whereas those of the other subfamilies are medium-sized, except for Brocchinia reducta, which has small pollen grains. All pollen grains are monosulcate with a simple sulcus, although a diffuse sulcus has been reported in the literature for Navia arida. The aperture margin is type III in all species examined, except Lindmania piresii, which exhibits a type I margin. Ornamentation is predominantly reticulate, except in Brocchinia paniculata, Navia lactea, and Brocchinia acuminata, which have perforate ornamentation. Several results presented here are unprecedented and contribute to expanding current knowledge of pollen morphology in the five subfamilies analyzed.