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

Leaf structure and ultrastructure changes induced by heat stress and drought during seed filling in field-grown soybean and their relationship with grain yield

Studies focusing on terminal drought combined with heat impacts on plants of agronomic value remain scarce, and even less under field conditions. The objective of this study was to investigate leaf structural and ultrastructural changes induced by heat stress (HS) and drought stress (DS) during seed filling and their relationship with physiological variables and yield determination. Two soybean cultivars were grown in field conditions. During seed filling four treatments were applied, including a control (without manipulation, at ambient temperature and field capacity), HS (episodes exceeding 32°C for 6 h d-1) during 21-d, DS (20% of field capacity soil water content) during 35-d, and HS×DS. Drought principally reduced leaf area, whereas heat decreased leaf thickness, possible as acclimation strategies, but also irreversible reducing CO2 assimilation sites. Both stresses damaged the outer and inner membranes of chloroplasts, causing swollen chloroplasts and accumulation of plastoglobules, loss of chlorophyll content, and negatively affecting chlorophyll fluorescence. Thus, the performance and integrity of the photosynthetic machinery were reduced. Through a morpho-functional perspective and a holistic multiscale approach, our results provide evidence of photosynthesis impairment and yield drops under stressful conditions which were associated with structural and ultrastructural (particularly at the level of chloroplasts) modifications of leaves.Instituto de Fisiología y Recursos Genéticos VegetalesFil: Carrera, Constanza Soledad. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales; ArgentinaFil: Carrera, Constanza Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Estudios Agropecuarios (UDEA); ArgentinaFil: Solis, Stella M. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica del Nordeste (IBONE); ArgentinaFil: Solis, Stella M. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Cátedra de Morfología Vegetal; ArgentinaFil: Ferricci, María S. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ferricci, María S. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica del Nordeste (IBONE); ArgentinaFil: Vega, Claudia Rosa Cecilia. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Manfredi; ArgentinaFil: Galati, Beatriz G. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Botánico General; ArgentinaFil: Ergo, Verónica Vanesa. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Fisiología Vegetal; ArgentinaFil: Ergo, Verónica Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Estudios Agropecuarios (UDEA); ArgentinaFil: Andrade, Fernando Hector. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce. Ecofisiología de cultivos; ArgentinaFil: Andrade, Fernando Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; ArgentinaFil: Lascano, Hernán Ramiro. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Fisiología Vegetal. ArgentinaFil: Lascano, Hernán Ramiro. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Estudios Agropecuarios (UDEA). Argentin

Anatomical studies of the secretory structures: glandular trichomes and ducts, in Grindelia pulchella Dunal (Astereae, Asteraceae)

The ultrastructure of the glandular trichomes and secretory ducts of Grindelia pulchella was studied. Plastids, mitochondria and endoplasmic reticulum are involved in the secretory process of both, trichomes and ducts. A special tissue with “transfer cells” is associated with the duct epithelial cells. The secretion is produced in the transfer cells and then is transferred to the duct epithelial cells where it accumulates in the vacuoles. The occurrence of cavities within the cell walls of the trichome cells and duct epithelial cells is described. The secretion is accumulated between the cell wall and the cuticle of these cells. When the cuticle is broken the secretion is released. We conclude that granulocrine secretion operates in this species.Fil: Bartoli, Adriana. 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: Tortosa, Roberto Daniel. 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. Oficina de Coordinación Administrativa Parque Centenario; 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

Pollen, Tapetum and Orbicule Development in Modiolastrum malvifolium (Malvaceae)

• Background and Aims: Although orbicular functions are still a matter of debate, they are considered by most authors to be exclusively formed by a secretory tapetum. However, the presence of orbicules on a peritapetal membrane associated with a plasmodial tapetum has been described for Abutilon pictum (Malvaceae) in a previous study. Thus, studies on other species of Malvaceae are necessary to corroborate the presence of such bodies in other members of the family. Pollen and microsporangium development of Modiolastrum malvifolium has been studied in this work. • Methods: Anthers at different stages of development were processed for transmission electron microscopy and light microscopy. Membranes and pollen walls resistant to acetolysis were isolated from whole anthers. • Key Results: Microspore tetrads have a tetrahedral arrangement. Pollen grains are shed at the bicellular stage. The tapetum is invasive, non-syncytial and a peritapetal membrane with orbicules is formed. • Conclusions: This is the first report of the presence of orbicules on a peritapetal membrane in a species with a tapetum of an invasive, non-syncytial type. Taking into consideration all the information on the subject, it can be concluded that the presence of orbicules is not a stable criterion to differentiate between a secretory or plasmodial, or intermediate invasive, non-syncytial tapetum. © The Author 2007. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.Fil:Galati, B.G. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Monacci, F. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Gotelli, M.M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Rosenfeldt, S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Ultrastructure of the corona of scented and scentless flowers of Passiflora spp. (Passifloraceae)

To know thoroughly the structure and function of the corona of Passiflora, the anatomy and ultrastructure of two species were analysed in relation to the emission of odour perceivable by humans: a scented one, P. caerulea L., and a scentless one, P. suberosa L. Both species exhibited secretory tissue, whose cells were characterised by dense cytoplasm, numerous mitochondria and vacuoles. Evidence of granulocrine secretion was detected. Nevertheless, there were differences concerning some cytological structures: P. suberosa lacked smooth endoplasmic reticulum (sER) and starch but had large and many lipidic globules, while P. caerulea had few dictyosomes, scarce lipidic content, a greater proportion of sER/rough endoplasmic reticulum (rER) and amyloplasts. The cellular features of P. caerulea correspond with those of fragrance tissues. The secretion appearance and quantity were also different between both species: P. caerulea exhibited sparse drops on the cuticle in contrast to P. suberosa, which secrets a wax-like material. If this is the final product of the secretory process or just a vehicle that contributes to the emission of volatile compounds, as occurs in certain osmophores, needs further confirmation with chemical analysis. Results are discussed in the context of the pollination syndromes of each species and their florivores.Fil: Amela Garcia, Maria Teresa. 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; ArgentinaFil: Galati, Beatriz G.. Universidad de Buenos Aires; 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

Pollen content accumulated in nests of Polybia scutellaris (Hymenoptera, Vespidae)

Plant resources foraged by Polybia scutellaris were identified by analysing the pollen content of 14 nests in Magdalena (Buenos Aires Province, Argentina). Six nests were inhabited at the time of collection. The palynological analysis indicated that the wasps visited 33 different taxa of flowering plants during the active cycle of the colonies. Flowers visited by the wasps belonged to both native and exotic plants located close to the nests. The variety of resources foraged by P. scutellaris characterises this species as a generalist flower visitor.Fil: Fernandez Corujo, Victoria Lilian. Universidad de Buenos Aires. Facultad de Agronomia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Basilio, M. Alicia. Universidad de Buenos Aires. Facultad de Agronomia; ArgentinaFil: Galati, Beatriz G.. Universidad de Buenos Aires. Facultad de Agronomia; Argentin

Chloroplast dimorphism in leaves of Cabomba caroliniana (Cabombaceae)

Cabomba Aublet is useful as a genetic model of angiosperm evolution. Previous anatomical studies and preliminary light microscopic observations on C. caroliniana A Gray revealed the presence of dimorphic chloroplasts in both types of leaves, floating and submerged leaves. Leaf anatomy and chloroplasts ultrastructure were analyzed and compared. The chloroplast ultrastructure of the mesophyll and epidermal cells is different. Mesophyll chloroplasts have several plastoglobuli, large starch grains and grana formed by an average of 29 thylakoids. Epidermal chloroplasts are smaller, have grana formed by an average of 9 thylakoids and starch grains are occasional and smaller. A statistical analysis (t-test) was made to determine if differences between chloroplasts are significant. The ultrastructure of the epidermis chloroplast is similar to the one of sun leaves chloroplasts and the ultrastructure of the mesophyll chloroplast is similar to the one of shade chloroplast observed in other species.Fil: Galati, Beatriz G.. Universidad de Buenos Aires. Facultad de Agronomia. Cátedra de Botanica General; ArgentinaFil: Gotelli, Marina María. Universidad de Buenos Aires. Facultad de Agronomia. Cátedra de Botanica General; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rosenfeldt, Sonia. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; ArgentinaFil: Lattar, Elsa Clorinda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botanica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botanica del Nordeste; ArgentinaFil: Tourn, G. Mónica. Universidad de Buenos Aires. Facultad de Agronomia. Sede Polo Universitario Punilla Centro; Argentin