Structure of the stigma and style in sunflower (Helianthus annuus L.)

This is the first report of the ultrastructure of the stigma and style during and after anthesis in Helianthus annuus L. using light and transmission electron microscopy. The stigma is bifid with unicellular papillae. There is no secretion of lipids, carbohydrates or proteins at anthesis. The style is semisolid in the upper portion, closer to the stigma, and becomes solid below. Ultrastructural changes on cells of the stigma and the style are described. The transmitting tissue of the ovule is first evident 40 minutes after pollination and persists during the first stages of embryogenesis. Only one pollen tube per micropyle was observed growing through this tissue.Fil: Gotelli, Marina María. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Galati, B. G.. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; ArgentinaFil: Medan, Diego. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Pollen ontogeny in Magnolia liliflora Desr

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.Fil: Galati, Beatriz Gloria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; ArgentinaFil: Zarlavsky, G. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; ArgentinaFil: Rosenfeldt, S.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; ArgentinaFil: Gotelli, Marina María. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Are the floral morphology and anatomy of Galphimia australis, an atypical neotropical Malpighiaceae, associated to a new pollination syndrome?

The flowers of the species of Malpighiaceae in the Neotropical Region are relatively uniform in their morphology due to their dependence on oil-collecting bees as their main pollinators. However, many species of the genus Galphimia seem to have acquired a different floral syndrome, lacking markedly zygomorphic flowers and developed elaiophores in the calyx. Likewise, these species present anthers with great development, probably in response to the selection of pollinators that collect pollen. Galphimia australis incorporated some of these traits but also retained some residual characteristics typical of species pollinated by oil bees. This leads to many questions on how these flowers ensure their pollination. Inquiring about the reduction or modification of these characteristics allows us to understand how G. australis achieves a different pollination syndrome. In this research, we carry out a detailed morphological and anatomical study of the flowers and pollen grain devolvement of G. australis and floral visitors were observed and captured. Results were analyzed in order to determine how this species changed from the oil-floral syndrome, typical of neotropical Malpighiaceae, to one syndrome with pollen as the main reward.Fil: Gotelli, Marina María. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; ArgentinaFil: Aliscioni, Sandra Silvina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Kuo, P. T.. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; ArgentinaFil: Torretta, Juan Pablo. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Nectary ultrastructure of Cabomba caroliniana Gray (Cabombaceae)

Cabomba Aubl. is a genus considered as a potential genetic model for studies of early angiosperm evolution, accordingly, it is important to expand the knowledge of it. This paper reports the study of the anatomy and the ultrastructure of the nectary of Cabomba caroliniana Gray using bright-field microscope, scanning and transmission electron microscope in order to understand its secretion mechanism. C. caroliniana has protoginous flowers and the anthesis lasts two days. Nectaries of C. caroliniana are located in two basal lobes or yellow auricles of each white petal. Most nectar is observed in the area above the pronounced auricles. The secretion is released mainly by the four-cellular trichomes or hydropotens present in both nectary epidermis. The cellular ultrastructure indicates that the nectary is active during the two days of the anthesis. This agrees with the fact that in both anthesis days the fertile structures of the flower (first the stigmata and then the anthers) are disposed above the nectaries. The nectar secretion mechanism is discussed in relation to the present knowledge. The results of this study are related to what has been described for other basal angiosperms.Fil: Galati, Beatriz Gloria. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Botánica General; ArgentinaFil: Gotelli, Marina María. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Botánica General; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Fabbri, Liliana Teresa. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Botánica General; ArgentinaFil: Rosenfeldt, Sonia. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; ArgentinaFil: Zarlavsky, Gabriela Elena. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Botánica General; Argentin

Morphological and ultrastructural studies of floral nectaries in Rhamnaceae

Morphology, anatomy and ultrastructure of nectaries of 12 species belonging to five tribes of Rhamnaceae (Pomaderreae, Colletieae, Paliureae and Gouanieae of the Ziziphoids clade, and Rhamneae of the Rhamnoids clade) are studied by light and electron microscopy. Four types of nectaries are observed in this study. Species of the tribes Rhamneae, Gouanieae, Paliureae and Cryptandra tomentosa of the Pomaderreae tribe have annular nectaries. Siegfriedia darwinioides and Stenanthemun humile (Pomaderreae) show revolute nectaries, along with Colletia paradoxa and C. spinossisima (Colletieae). Retanilla patagonica and Kentrothamnus weddellianus (Colletieae) have indistinct and adpressed nectaries respectively. Nectar secretion occurs through modified nectary stomata in all species. Differences in the ultrastructure, mode of nectar secretion and position of the nectaries are discussed. According to the organelles found in nectary cells of all the species studied, granulocrine secretion is most likely to occur. Further research of these structures in more species of this family could help to establish nectary homologies.Fil: Gotelli, Marina María. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; ArgentinaFil: Galati, Beatriz G.. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; ArgentinaFil: Medan, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentin

Embryology of sunflower Helianthus annuus (Asteraceae)

The abortion of sunflower fruits during different moments of its development could be due to abnormalities in the reproductive process. A comparative study of the sporogenesis, gametogenesis and the development of the related sporophytic structures on three commercial hybrids, DK 4050, CF 17 and P30, and a line, HA 89 is reported. The anther wall consists of epidermis, endothecium, one middle layer and a plasmodial tapetum with binucleate cells  efore integrating. A peritapetal membrane with orbicules encloses the pollen grains, which are triporate, angulaperturate and shed at tricellular stage. HA89 also presents tetraporate pollen grains. The ovule is tenuinucelate, unitegmic and anatropous. The young embryo-sac is formed by six cells and eight nuclei. Antipodes, which vary in number and in the amount of nuclei on their cytoplasm, usually show thick walls between themselves and the middle cell. Differences between the genotypes studied may justify the contradictions found on previous accounts.The abortion of sunflower fruits during different moments of its development could be due to abnormalities in the reproductive process. A comparative study of the sporogenesis, gametogenesis and the development of the related sporophytic structures on three commercial hybrids, DK 4050, CF 17 and P30, and a line, HA 89 is reported. The anther wall consists of epidermis, endothecium, one middle layer and a plasmodial tapetum with binucleate cells  efore integrating. A peritapetal membrane with orbicules encloses the pollen grains, which are triporate, angulaperturate and shed at tricellular stage. HA89 also presents tetraporate pollen grains. The ovule is tenuinucelate, unitegmic and anatropous. The young embryo-sac is formed by six cells and eight nuclei. Antipodes, which vary in number and in the amount of nuclei on their cytoplasm, usually show thick walls between themselves and the middle cell. Differences between the genotypes studied may justify the contradictions found on previous accounts.Fil: Gotelli, Marina María. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental. Laboratorio del Grupo de Estudio de Plantas Vasculares; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Galati, Beatriz Gloria. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental. Laboratorio del Grupo de Estudio de Plantas Vasculares; ArgentinaFil: Medan, Diego. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Structure and ultrastructure of the stigma and style of Luehea divaricata (Malvaceae-Grewioideae)

Luehea Milld. is a Neotropical genus with 18 species. This paper reports the study of the structure and the ultrastructure of the stigma and the style of Luehea divaricata Milld. using bright-field microscope and transmission electron microscope. Multiseriate papillae are observed in the stigma. The papillae cells are large with a content that stains intensively and the sub-stigmatic tissue resembles the style’s transmitting tissue. L. divaricata has a closed style with an epidermis that presents raised stomata and multicellular trichomes. Numerous organelles and a large nucleus are present in the dense cytoplasm of the transmitting tissue cells. A relevant feature is that the cells of this tissue in the species studied present a very thick middle lamella with two zones of different electron density in the angle of contact between cells, and convex lens-shaped thickenings of the cell wall are prominent mainly also in these angles of contact. The growth of the pollen tube is initiated on the stigmatic papillae surface and continues growing in the middle lamella of the sub-stigmatic tissue and the transmitting tissue, mainly at the contact angle between cells. The present work is the first contribution to the knowledge of structure and ultrastructure of the stigma and style in the genus Luehea, as well as to the subfamily Grewioideae (Malvaceae).Fil: Lattar, Elsa Clorinda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Gotelli, Marina María. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Botánica General; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: Galati, Beatriz. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Botánica General; Argentin

Embryology of Macroptilium arenarium (Leguminosae)

Macroptilium arenarium (Bacigalupo)S.I.Drewes & Palacios produces two floral morphs, aerial chasmogamous flowers and cleistogamous flowers in geophyte racemes. A comparative study of the sporogenesis, gametogenesis and the development of the related sporophytic structures in both floral morphs is reported. The anther is tetrasporangiate, its wall consists of epidermis, endothecium, one or two middle layers and an uninucleate secretory tapetum. The mature endothecium presents fibrilar thickenings that are more developed in cleistogamous flowes. Pollen grains are tricolporate, angulaperturate, and are shed at bicellular stage. The ovule is crassinucelate, bitegmic and anacampylotropous. Megaspore tetrads with linear arrangement have been observed in chasmogamous flowers, whereas only megaspore dyads have been found in cleistogamous flowers. In both floral morphs the chalazal megaspore develops into an embryo sac of Polygonum type. Apomixis is considered as a possible replacement for sexual reproduction in cleistogamous flowers.Fil: Gotelli, Marina María. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Galati, Beatriz Gloria. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Hoc, Patricia Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; Argentin

Gynoecium with carpel dimorphism in Tricomaria usillo, comparison with other genera of the Carolus clade (Malpighiaceae)

We analyzed the gynoecium morphology and anatomy of Tricomaria usillo in young and mature flowers from diverse populations in order to analyze the differentiation of structure and function of the parts of the carpel. We also aimed to find the potential pollinators and associate the morphology of the gynoecium with its role. We compare the characteristics of the gynoecium of T. usillo and discuss the carpel dimorphism with other genera within the Carolus clade in relation with their pollination syndromes. Carpels were processed according to classic techniques for scanning electron microscopy and bright field microscopy. We conducted field observation in different populations of T. usillo and captured the insects that were identified to specific level. The gynoecium of T. usillo shows inter-population and intra-individual variability. Some have three well-developed carpels, while most of them present two posterior carpels with differentiated styles and stigmas and the anterior one with a shorter style with or without stigma. The ovary has three locules with one ovule each. A compitum is formed and all ovules may be fecundated. However, fruits have generally one seed that develops in the anterior locule. Centris brethesi is the potential pollinator. The gynoecium of T. usillo reflects part of the variation in the carpel dimorphism that probably arose in the branch of the Carolus clade, and evolved in diverse ways in the lineages of this group. Tricomaria usillo seems to represent a recent transition towards reaching a stable form of carpel dimorphism and definitive division of labors of the carpels.Fil: Aliscioni, Sandra Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Botánica General; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: Gotelli, Marina María. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Botánica General; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: Torretta, Juan Pablo. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Botánica General; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentin

Anatomy and ultrastructure floral osmophores of Catasetum fimbriatum (Orchidaceae)

Catasetum fimbriatum is a dioecious species whose flowers fully adapted to an euglossinophilic mode of pollination. Euglossini male bees collect the volatile fragrances which are produced in osmophores on the flowers. In order to understand the mechanism of scent secretion and floral interaction with the pollinator, we describe the location, histochemistry, anatomy, and ultrastructure of osmophores in pistillate and staminate flowers of this species. Fresh flowers were submerged in neutral red solution to locate the position of the osmophores. Other histochemical test performed includes the NADI reaction to detect terpenoids, Sudan IV for lipids, and Lugol’s iodine solution to detect starch. Anatomical and ultrastructural traits were studied with bright field and transmission electron microscopes, respectively. The location of osmophores differs between pistillate and staminate flowers. In pistillate flowers, secretory tissues were observed on the ribbed adaxial surface of the labellum, but not on its margins, whereas in staminate flowers, they were found throughout the adaxial surface of the labellum and especially in the fimbriae. Anatomy and ultrastructure of the osmophores in the labellum of both types of flowers were similar. They present characteristics of metabolically active cells, such as abundant mitochondria, rough endoplasmic reticulum, vesicles, plastids with starch grains, and lipid globules. Granulocrine secretion and cycles of cytoplasmic contraction and expansion appear to allow the release of products without involving the rupture of the cuticle. Individuals of Eufriesea auriceps and Euglossa sp. were captured in staminate and pistillate flowers but, it seems likely, that only the former pollinates this orchid species.Fil: Reposi, Sofía Daniela. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; ArgentinaFil: Gotelli, Marina María. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; ArgentinaFil: Torretta, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Botánica Agrícola; Argentin