Beyond SEM: Stigmatic margins in Bromeliaceae

Abstract

Bromeliaceae is one of the most diverse families in terms of morphology, especially its floral structure and stigmatic variability. Nineteen different stigmatic types are observed in the family, the margins of which differ in shape and presence or absence of epidermal appendages. Although many studies have classified stigma types, those that report on stigmatic margins are rare. Therefore, in this work, we aimed to study in detail the morphology of stigmatic margins in Bromeliaceae, including micromorphology and histochemistry, characterizing the secretions produced. To accomplish this, we used both optical and electron microscopy. Stigmatic margins of the twenty-two species studied were described as crenate, laciniate, lobate, undulate, and entire. We also observed unicellular, bicellular and multicellular secretory trichomes, branched or unbranched, with two to five arms. Stigmatic secretions, such as mucilage, total lipids, starch, polysaccharide, alkaloid and essential oil, were found. By addressing the diversity of stigmatic margins, we have added to the systematics of Bromeliaceae, including the morphology and histochemistry of epidermal appendages.