Nectary ultrastructure and secretory modes in three species of Tillandsia L. (Bromeliaceae) that have different pollinators

The floral nectaries of three Tillandsia species having different pollinators were investigated with transmission electron microscopy (TEM) to describe the previously unstudied ultrastructure of the nectar-producing tissues (mainly the epidermis) and also to determine if any differences in the ultrastructural features could be correlated to pollination mode. We determined that there were variations in nectaries among the three species, and that these may be linked to pollinator choice Tillandsia seleriana, which has a strict relationship with ants, had a nectary epithelium characterized by abundant dictyosomes and ER, and a final degeneration stage possibly leading to holocrine secretion. The presence of protein crystals in epithelial plastids was correlated to a nectar enriched with amino acids and proteins, likely functioning to provide a protein-enriched diet and possibly defence against pathogens. Epithelial cells of the hummingbird-pollinated T. juncea nectary displayed cell wall ingrowths and dictyosomes and also contained cytoplasmic lipid droplets and protein crystals within plastids, both of which would enrich the nectar for hummingbirds. The nectary epithelium and even the parenchyma of bat-pollinated T. grandis possessed a few cubic protein crystals in the plastids, and its secretion product appeared electron transparent.