Comparative floral anatomy of 10 species of Myrteae (Myrtaceae) and phylogenetic implications

This study evaluated and described the comparative floral anatomy of Myrteae species to facilitate species characterization. Buds and flowers collected from the herbarium were subjected to herborization reversion, and the fresh material was prepared using standart techniques, for further analysis with a light optical microscope. There was little variation in the tissues that comprise the floral whorls of the studied species. Bracteoles were observed in six taxa, and the mesophyll may consist of fundamental or spongy parenchyma. The vascular bundles of the pedicel, with a siphonostelic arrangement, are individualized in a monocycle of eight to ten vascular bundles from the base of the ovary. The ovary wall has three regions in the mesophyll composed of fundamental or spongy parenchyma: the outer region, which contains secretory cavities; the median region, which contains large vascular bundles of the monocycle; and the inner region, which contains carpellary vascular bundles. In the perianth, the number of vascular bundles varies, and they are surrounded by fundamental or spongy parenchyma. The ovules are campylotropous. The anthers are tetrasporangiate, but in Eugenia uniflora, there is no secretory cavity in the connective. The number of vascular bundles in the style varies from four to seven. Characteristics that may indicate evolutionary trends and that should be explored further include: (1) the ratio of placental height to ovule number (2) the ratio of the number of vascular bundles of the monocyclic to the number of carpels, and (3) the presence of secretory cavities in the inner part of the hypanthium. These findings contribute to the phylogenetic resolution and systematic understanding of Myrteae.