CONICET | Buscador de Institutos y Recursos Humanos

Background and Aims: Most studies in Anacardiaceae embryology have focused in seed and fruit development in different genera. None of them, however, included species of Schinopsis. Considering the absence of embryological data and the precedents of chalazogamy in the Anacardiaceae family, the aims of this study were to complete the embryological studies in S. balansae, providing information about male and female sporogenesis and gametogenesis, fertilization and embryogenesis and investigate the developments of the gynoecium and pathway of pollen tube.?Methods: Flowers and fruits S. balansae, a dioecious tree from Anacardiaceous family, were collected and fixed in the field. The embryology was examined using light microscopy, fluorescence microscopy and scanning electron microscopy. Microtome section series were used to reconstruct the morphology and pollen-tube pathway.?Key Results and Conclusions: The functionally pistillate flowers have a superior tricarpellar ovary, three free styles with capitated stigmas. One fertile carpel with one locule and single anatropous crassinucellar and unitegmic ovule; two aborted and lateral carpels that do not produce ovule nor form locule. Embryo sac development conformed to the Polygonum type. Pollen grains germinate on stigma, penetrate the transmitting tract inside the styles. At apical portion of ovary, pollen tubes grow through the carpel wall and reach the vascular bundle inside the ovule´s funicle where they branches off. One branch continues crossing the vascular bundle to the chalaza, encircled the embryo-sac reaching one synergid. Fertilization was aporogamous; the term funiculogamy was proposed to define this type of pollen tube penetration. Well-developed stamens without sporogenous tissue are present in the pistillate flowers. Staminate flowers only have a rudimentary pistil; the anthers are bithecal and tetrasporangiate. The tapetum is secretory, uninucleate; the pollen grains are bicellular. Embryos follow the Onagrad type. The endosperm development is coenocytic/multicellular type.