The flower of Myrtus communis (Myrtaceae): Secretory structures, unicellular papillae, and their ecological role

Abstract Secretory cavities, unicellular papillae and hair trichomes of the flower of Myrtus communis have been investigated morphologically, anatomically and histochemically. Secretory cavities located adjacent to the epidermis of sepals, petals, receptacle, stamens, ovary and style show both a schizolysigenous, a combination of schizogenous and lysigenous development. At maturity, the glands are made up of a sheath of flattened cells; secretory cells are completely degenerated. The presence of lipids, terpenes and phenolics identified in the secretory lumen may be linked to different ecological functions especially depending on the organ where glands are distributed. Unicellular papillae are located on the upper surface of the ovary close to the base of the stamens. They do not seem to form a nectary, but phenolic production by parenchymal cells beneath them could be linked to the production of volatile secretions as attractants for pollinators. Hair trichomes are generally made of a single-basal cell, one stem cell and a cap cell. They are present on the upper surface of the ovary among unicellular papillae. It could be assumed that these hairs have a generic protective role for the ovary.