The floral nectaries are associated with the androecium.Vivipary, the germination of seeds before they are shed from the parent plant, is a rare event in angiosperms involving complex ecophysiological processes. In the centre of the ovary a primordium arises that develops into the single basal circinotropous bitegmic ovule. Continuity between the gynoecial primordia is reached earlier in the Plumbagoideae than in the Armerioideae. These primordia soon reach continuity and develop into the superior unilocular gynoecium. After inception of the common primordia, five gynoecial primordia alternating with the common primordia are initiated simultaneously on the corners of the apex that has become pentagonal. Soon, two distinct growth-centres can be observed on each of these primordia: a petal primordium at the abaxial side and a stamen primordium on the top. Meanwhile, five common stamen-petal primordia that alternate with the sepal primordia are initiated simultaneously on the flattened apex. These soon reach continuity and develop into the synsepalous calyx. The five sepal primordia are initiated simultaneously or spirally. The early ontogenetic stages in all species examined are sufficiently similar to propose the following familial description. The ovules are circinotropous, bitegmic, crassinucelate, and have long funiculus as in many other Cactaceae.Ī scanning electron microscopic study of the floral ontogeny of seven species of the Plumbaginaceae (representing five genera of the Armerioideae and two of the Plumbagoideae) is presented. The stigma has 9-10 lobes with a secretory epidermis. The nectariferous region occurs on the inner surface of the hypanthium. The ovary has inverted vascular bundles in a similar pattern as in Pereskia. The gynoecium is syncarpous with 9-10 carpels, pluriovulate, and with parietal placentation. The wall of the young anther is formed by epidermis, endothecium, a middle layer, and binucleate secretory tapetum that eventually becomes uninucleate. The androecium has many stamens with tetrasporangiate and bithecal anthers. Secretory cavities containing mucilage and calcium oxalate crystals occur throughout the fl oral parenchymatous tissue. All fl ower whorls have uniseriate epidermis. The fl ower is sessile and epigynous with a well-developed hypanthium. Flowers and fl ower buds were collected in Maringá, Paraná State, Brazil, fi xed, processed, and analyzed under light microscope and scanning electron microscope. The aim of this contribution was to analyze the morpho-anatomical fl oral structure of Epiphyllum phyllanthus (L.) Haw., a widely distributed species across South America, occurring in humid forests as an epiphyte.
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January 2023
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