Showing papers by "Beatriz G. Galati published in 2012"
TL;DR: The granular infratectum of the ectexine and the presence of orbicules could indicate that this species is one of the most evolved of the genus, Magnoliaceae.
Abstract: Pollen ontogeny contributes significantly to the evolutionary analysis and the understanding of the reproductive biology of seed plants. Although much research on basal angiosperms is being carried out there are still many important features about which little is known in these taxa, such as the sporophytic structures related to pollen development and morphology. In this study, pollen development of Magnolia liliflora was analyzed by optical microscopy and transmission electron microscopy. The aim of this paper was to supply data that will help characterize basal angiosperms. Microsporogenesis is of the successive type, so that tetrads are decussate or isobilateral. The callosic walls form by the centripetal growth of furrows. The secretory tapetum develops orbicules, which start to form in the microspore tetrad stage. Pollen grains are shed at the bicellular stage. The exine wall has a granular infratectum. Ultrastructural changes observed in the cytoplasm of microspores and tapetal cells are related to the development of the pollen grain wall and orbicules. Centrifugal cell plates are more usual for the successive type of microsporogenesis. The presence of the successive type of microsporogenesis with callosic walls formed by the centripetal growth of furrows could reflect the fact that the successive type in Magnoliaceae is derived from the simultaneous type. The granular infratectum of the ectexine and the presence of orbicules could indicate that this species is one of the most evolved of the genus.
17 citations
TL;DR: The proorbicules have the appearance of lipid globule, and their formation is related to the endoplasmic reticulum of rough type (ERr), the first report on the presence of orbicules in the family Rhamnaceae.
Abstract: Tapetum, orbicule, and pollen grain ontogeny in Colletia paradoxa and Discaria americana were studied with transmission electron microscopy (TEM). The ultrastructural changes observed during the different stages of development in the tapetal cells and related to orbicule and pollen grain formation are described. The proorbicules have the appearance of lipid globule, and their formation is related to the endoplasmic reticulum of rough type (ERr). This is the first report on the presence of orbicules in the family Rhamnaceae. Pollen grains are shed at the bicellular stage.
14 citations
TL;DR: This work is the first contribution to the knowledge of ultrastructural pollen development in the genus Luehea, as well as in the subfamily Grewioideae, and highlights the presence of multinucleate tapetal cells, which acquire ultrastructureural features characteristic of transfer cells at the young pollen grain stage, and which are associated with the existence of orbicules.
11 citations
TL;DR: The production of only a few viable pollen grains and the absence of successful megagametophyte development prevent fertilization and account for the disappearance of fruits and seeds formation in Oxalis debilis.
Abstract: The study of pollen and female gametophyte development of Oxalis debilis was carried out to elucidate the reasons for the absence of seed production in this species The formation of an incomplete callosic wall separating the microspores of the tetrad was observed; therefore, cytoplasm connections were present between the microspores Microspores of different sizes and with different grades of vacuolation were observed in the mature anther Only few microspores divide mitotically and form the generative and vegetative cell The cytoplasm of the vegetative cell may accumulate different substances in reserve Pollen grains are 8–12 colpate, and the morphology and electron density of the exine varies Because flowers in full anthesis have all ovules at the megasporocyte stage with the nucellar epidermis intact, fecundation could not occur The production of only a few viable pollen grains and the absence of successful megagametophyte development prevent fertilization and account for the absence of fruits and seeds formation
8 citations
TL;DR: The purpose of the study was to contribute a full description of possible interactions between the male gametophyte and the sporophytic tissues of the stigma and the style.
Abstract: The ultrastructure of the stigmas and styles of Colletia paradoxa, Colletia spinosissima, and Discaria americana was studied by transmission electron microscopy before and during anthesis. The purpose of the study was to contribute a full description of possible interactions between the male gametophyte and the sporophytic tissues of the stigma and the style. Ultrastructure changes in the stigmatic papillae and epithelial and sub-epithelial cells of the stylar channels in relation to pollen tube growth are discussed and compared between species. New pollen tube pathways are described for hollow styles.
5 citations
Journal Article•
TL;DR: Anthers of ten species of Poaceae from the province of Buenos Aires (Argentina) were investigated with scanning and transmission electron microscopes and four different types and four subtypes of orbicules were identified.
Abstract: Summary: Orbicules diversity in Poaceae. Anthers of ten species of Poaceae from the province of Buenos Aires (Argentina) were investigated with scanning and transmission electron microscopes. The orbicules can be defined as corpuscles of variable size that show the same electron-density, reaction to the dyes, autofluorescence and resistance to acetolysis as pollen exine does. The orbicules are randomly dispersed on the inner anther locule and they are often attached to a tapetal membrane. In this study, four different types and four subtypes of orbicules were identified. We conclude that the different orbicules types described in this work are representative of the studied tribes, and we suggest that the orbicules morphology may be a useful character in systematic studies.
5 citations
TL;DR: These observations constitute the first report on the ultrastructure of pollen in the Linaceae that characterizes the species here studied and expands the palynological knowledge of this family.
Abstract: We report a detailed study of the pollen wall structure in Linum burkartii and L. usitatissimum (Linaceae). This study was carried out using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results confirm that the exine of the species studied is formed by: the ectexine constituted by clavae, gemmae, and a loose basal layer, a thin endexine and a fibrilar intine. These observations constitute the first report on the ultrastructure of pollen in the Linaceae that characterizes the species here studied and expands the palynological knowledge of this family.
5 citations
30 Jul 2012
TL;DR: The mature anther wall of Cestrum bigibbosum consist of a papillae epidermis and one layer of endothecium as mentioned in this paper, showing periclinal division in some zones.
Abstract: The mature anther wall of Cestrum bigibbosum consist of a papillae epidermis and one layer of endothecium. The development of the anther wall retrieves the dicotyledoneous type, showing periclinal division in some zones of the middle layer. The endothecium shows a reticulate pattern of thickening, with more branches in the central region of the cell. The tapetum is secretory and degenerates at the free microspore stage. Microspore tetrads are tetrahedral and the pollen grain is two-celled at the shedding stage. Taxonomic significance of male gametophyte is discussed.
01 Jan 2012
TL;DR: The mature anther wall of Cestrum bigibbosum consist of a papillae epidermis and one layer of endothecium, which retrieves the dicotyledoneous type and taxonomic significance of male gametophyte is discussed.
Abstract: The mature anther wall of Cestrum bigibbosum consist of a papillae epidermis and one layer of endothecium. The development of the anther wall retrieves the dicotyledoneous type, showing periclinal division in some zones of the middle layer. The endothecium shows a reticulate pattern of thickening, with more branches in the central region of the cell. The tapetum is secretory and degenerates at the free microspore stage. Microspore tetrads are tetrahedral and the pollen grain is two-celled at the shedding stage. Taxonomic significance of male gametophyte is discussed.