scholarly journals Morfogénesis de la fase sexual de los helechos epífitos Microgramma mortoniana y Pleopeltis macrocarpa (Polypodiaceae) reserva Natural Punta Lara, Buenos Aires, Argentina

2018 ◽  
Vol 66 (3) ◽  
pp. 1078
Author(s):  
Daniel Alejandro Gorrer ◽  
Pedro Cayetano Berrueta ◽  
Juan Pablo Ramos Giacosa ◽  
Gabriela Elena Giudice ◽  
Marìa Luján Luna
Keyword(s):  
Buenos Aires ◽  
Riparian Forest ◽  
Vegetative Reproduction ◽  
Life Cycles ◽  
Gametophyte Development ◽  
Equatorial Diameter ◽  
Natural Reserve ◽  
Polar Diameter ◽  
Systematic Group

The Punta Lara Natural Reserve is located on the riverside of the La Plata River in the province of Buenos Aires, Argentina. It is the Southern most relict in the world of subtropical riparian forest. The epiphytic ferns studied in this work belong to the Polypodiaceae family: Microgramma mortoniana and Pleopeltis macrocarpa. Plant communities are subject to high levels of anthropization and introduction of exotic species. The goals of this work are to provide information on the morphogenesis of epiphytic gametophytes and to extend knowledge of their life cycles, contributing to their conservation. Sowing was carried out in Dyer medium. In both species the spores are monolete, ellipsoidal, yellowish and with verrucate sculpture. The equatorial diameter is 60-61 μm, the polar diameter is 39-42 μm. The germination is the Vittaria type; in M. mortoniana occurs at 20 days, while in P. macrocarpa occurs at six days. The filaments are uniseriate of 3-6 cells in length. The gametophyte development is Drynaria type. The cordated form is given after 40 days. In M. mortoniana, buds originated after 40 days. In P. macrocarpa, after 120 days, clathrate trichomes scale-like appear mainly on the margins of the gametophyte. The gametangia are typical of leptosporangiate ferns. The sporophyte of M. mortoniana emerged after 120 days and that of P. macrocarpa arose after 500 days, its blades are simple, spatulate and unicellular and multicellular branching hairs were observed. The germination pattern, gametophyte development, the presence of a lipid globule in the prothalic cell and the formation of unicellular capitated hairs are relevant characters that could be considered for systematic group. The delay in the formation of sporophytes through sexual reproduction, allows us to infer that the success of their establishment in situ would be given by the vegetative reproduction through creeping rhizomes and buds of gametophytes.

Observing microscopic phases of lichen life cycles on transparent substrata placed in situ

2005 ◽  
Vol 37 (5) ◽  
pp. 373-382 ◽  
Author(s):  
William B. SANDERS
Keyword(s):  
Life Cycle ◽  
Developmental Stages ◽  
Life Cycles ◽  
Potential Significance ◽  
Free Living ◽  
Lichen Community ◽  
One Year ◽  
The One ◽  
Observation Period

The utility of plastic cover slips as a substratum for in situ study of lichen developmental stages is further explored in a neotropical foliicolous lichen community and in a European temperate corticolous community. Twenty-one months after placement in the tropical forest, the cover slips bore foliicolous lichen thalli with several species producing characteristic ascocarps and ascospores, indicating the suitability of the substratum for completion of the life cycle of these lichens. On cover slips placed within the temperate corticolous community, lichen propagules anchored to the substratum with relatively short attachment hyphae but did not develop further within the one year observation period. Intimately intermixed microbial communities of short-celled, mainly pigmented fungi and chlorophyte algae developed upon the transparent substratum. Among the algae, Trebouxia cells, often in groups showing cell division and without associated lichenizing hyphae, were commonly observed. The potential significance of the free-living populations in the life cycle of Trebouxia and in those of Trebouxia-associated lichen fungi is discussed.

scholarly journals Individual growth of Heleobia piscium in natural populations (Gastropoda: Cochliopidae) from the multiple use natural Reserve Isla Martin Garcia, Buenos Aires, Argentina

2008 ◽  
Vol 68 (3) ◽  
pp. 617-621 ◽  
Author(s):  
SM. Martin
Keyword(s):  
Buenos Aires ◽  
Natural Populations ◽  
Dynamic Structure ◽  
Reproductive Period ◽  
Individual Growth ◽  
Growth Equation ◽  
Multiple Use ◽  
Natural Reserve ◽  
Drainage Channels ◽  
The Individual

The present work analyses the individual growth of Heleobia piscium in natural conditions in coastal drainage channels of the Multiple Use Natural Reserve Isla Martín García, Buenos Aires, Argentina. Isla Martín García is located in the Upper Río de la Plata, to the south of the mouth of the Uruguay river (34° 11' 25" S and 58° 15' 38" W). Monthly collections were made from July 2005 to July 2006 in the eastern part of the island (Arena Beach). The population of H. piscium showed a complex and dynamic structure of sizes during a long period of the annual cycle. Two cohorts could be detected. The Bertalanffy growth equation was: Lt = 6 (1-e -1.85 (t+0.38)) and Lt = 3.9 (1-e -0.19 (t+4.84)) for cohorts 1 and 2, respectively. The pattern of population growth displayed a staggered model, where the greatest growth is observed during the summer. The reproductive period occurred during six months, from the beginning of summer to middle of fall. Based on only one reproductive effort, this pattern is not similar to that of other cogeneric species already studied.

scholarly journals Irrigation and fertigation frequencies with nitrogen in the watermelon culture

Bragantia ◽  
2014 ◽  
Vol 73 (2) ◽  
pp. 106-112 ◽  
Author(s):  
Carlos Newdmar Vieira Fernandes ◽  
Benito Moreira de Azevedo ◽  
Joaquim Raimundo Nascimento Neto ◽  
Thales Vinícius de Araújo Viana ◽  
Geocleber Gomes de Sousa
Keyword(s):  
Growth Performance ◽  
Shell Thickness ◽  
Citrullus Lanatus ◽  
Fruit Weight ◽  
Soluble Solids ◽  
Irrigation Frequency ◽  
Marketable Yield ◽  
Equatorial Diameter ◽  
Polar Diameter

This study evaluates the influence of different irrigation frequencies and different nitrogen fertigation frequencies on the growth performance of the watermelon (Citrullus lanatus) culture. Two experiments were conducted at the Paraguay farm in the Cruz municipality, Ceará, Brazil. They was randomized blocks design with six treatments and four replications. The irrigation frequency experiment consisted of the application of different irrigation frequencies. The treatments were: DM - daily irrigation in the morning with 100% daily dosage; DT - daily irrigation in the afternoon, with 100% daily dosage; DMT - twice daily irrigation, with 50% daily dosage in the morning and 50% daily dosage in the afternoon; 2D - irrigation every two days; 3D - irrigation every three days and 4D - irrigation every four days. To the experiment with different nitrogen fertigation frequencies, the treatments used were: 2F - 2 fertigations in a cycle; 4F - 4 fertigations in a cycle; 8F - 8 fertigations in a cycle; 16F - 16 fertigations in a cycle; 32F - 32 fertigations in a cycle and 64F - 64 fertigations in a cycle. We evaluated the marketable yield (PC), fruit weight (M), polar diameter (DP), equatorial diameter (DE), shell thickness (EC) and soluble solids (SS). The irrigation frequency treatments influenced all variables significantly, with twice daily irrigation (DMT, 50% in the morning and the 50% in the afternoon) promoting the highest productivity (69.79 t ha-1). The different frequencies of fertigation also significantly influenced all variables, except for the shell thickness, the highest yield (80.69 t ha-1) being obtained with treatment 64 fertigations in a cycle.

scholarly journals Influencia de las actividades agropecuarias intensivas en la hidrogeoquímica del acuífero freático en un sector de la cuenca alta del río Samborombón (Provincia de Buenos Aires, Argentina)

2020 ◽  
Vol 5 (2) ◽  
pp. 467-474
Author(s):  
Guido Esteban Borzi ◽  
Nicolas Jovic ◽  
Esteban Villalba ◽  
María Josefina Stein ◽  
Carolina Tanjal ◽  
...  
Keyword(s):  
Buenos Aires ◽  
Para Determinar ◽  
Del Rio

La cuenca del río Samborombón localizada en el noreste de la provincia de Buenos Aires es una cuenca rural donde, si bien domina la ganadería extensiva, han comenzado a desarrollarse en los últimos años establecimientos ganaderos intensivos. El engorde de ganado en corral genera gran cantidad de excretas que son una fuente puntual de contaminación del agua. En sectores donde el abastecimiento de agua para consumo es mediante la explotación del agua subterránea, estos focos de contaminación pueden limitar su potabilidad. El objetivo del trabajo fue evaluar la influencia de un corral de engorde en la hidroquímica del acuífero freático en la cuenca alta del río Samborombón, así como también analizar la vulnerabilidad social y el riesgo hídrico presente en el área. Para esto se efectuó la toma de muestras de agua para determinar iones mayoritarios, trazas y fósforo en laboratorio, midiéndose in situ el pH y la conductividad eléctrica. Los resultados indican que la ganadería intensiva constituye una actividad que tiende a deteriorar la calidad del acuífero freático mediante la incorporación de Cl-, SO42- y NO3-. Elementos inmóviles o poco solubles como los fosfatos tenderían a retenerse en el suelo y zona no saturada sin afectar al acuífero. Por su parte, los elementos traza no evidencian cambios respecto a los valores de fondo de la química en el área de estudio. La contaminación del acuífero por nitratos en algunos pozos supera el límite sugerido por la Organización Mundial de la Salud y afecta a los pobladores que viven en las adyacencias. Asimismo, se identificó una vulnerabilidad de tipo socioeconómica debido a la falta de acceso a servicios básicos, como el agua potable y un sistema cloacal adecuado.

scholarly journals Pollen morphology and availability of pollen and stigma in Syzygium (Myrtaceae)

2019 ◽  
Vol 41 (6) ◽  
Author(s):  
Guilherme Nacata ◽  
Talita Kely Belonsi ◽  
Eduardo Custódio Gasparino ◽  
Renata Aparecida de Andrade
Keyword(s):  
Flower Development ◽  
Pollen Morphology ◽  
Pollen Grains ◽  
Scanning Microscopy ◽  
Stigma Receptivity ◽  
Equatorial View ◽  
Equatorial Diameter ◽  
Species Overlap ◽  
Polar Diameter

Abstract The present study aimed to describe the pollen morphology in three species of Syzygium, to test pollen availability and stigma receptivity. The pollen was analyzed by light and scanning microscopy to show the detailed ornamentation of the pollen grains. Pollen availability was measured according to two protocols. Stigmatic receptivity was tested at different stages of flower development. There are differences among the pollen morphology for the species studied; when the polar and equatorial diameters are measured in the equatorial view of the pollen grains, it is observed that S. jambos is the largest species concerning the two values of the diameters, S. malaccense is the smallest species and S. aqueum, the largest species in relation to the polar diameter in the equatorial view. For the equatorial diameter in equatorial view, S. aqueum showed the smallest diameters and S. malaccense, the major diameters, but the two species overlap in the values of the measured diameters. There are variations in the number of apertures in the pollen grains. Alexander’s stain is more sensitive to estimate pollen availability and the species S. aqueum and S. jambos have the same schedules of pollen availability and stigma receptivity.

Dynamic Behavior and In-Situ Diagnostics of PEFCs

2006 ◽  
Author(s):  
Kaspar Andreas Friedrich ◽  
Till Kaz ◽  
Stefan Scho¨nbauer ◽  
Heinz Sander
Keyword(s):  
Fuel Cell ◽  
Density Distribution ◽  
Current Density ◽  
Single Cells ◽  
Current Density Distribution ◽  
Bipolar Plate ◽  
Life Cycles ◽  
Operating Conditions ◽  
Bipolar Plates

During fuel cell operation the electrochemical activity often is not homogenous over the electrode area. This may be caused by an non-uniform water content in the membrane, an inhomogeneous temperature distribution, and reactant gradients in the cell. Consequently a variation of the current density over the cell area occurs which tends to result in inferior performance. For in situ measurements of the current density distribution in fuel cell stacks a segmented bipolar plate was developed. The segmented bipolar plate was first tested in single cells with stack endplates to verify the function of all components. The tests showed that the measurement tool works very reliable and accurate. The insight in an operating fuel cell stack via current density distribution measurement is very helpful to investigate interactions between cells. Results can be used to validate models and to optimise stack components, e.g. flow field and manifold design, as well as to detect the best stack operating conditions. By applying segmented bipolar plates as sensor plates for stack system controls an improved performance, safe operation and longer life cycles can be achieved. The developed segmented bipolar plates with integrated current sensors were used to assemble a short stack consisting of 3 cells; each of them having an active area of 25cm2 divided into 49 segments. The design of the bipolar plate proofed very suitable for easy assembling of single cells and stacks. First measurement results show that different current distributions can appear in the cells and these can vary from cell to cell, depending on the operating conditions of the stack. Electrical coupling between the cells was investigated and found to be only marginal for the assembly used.

scholarly journals Pollen morphology in selected species of Caricaceae with special reference to novel palynological characters

Botany ◽  
2018 ◽  
Vol 96 (1) ◽  
pp. 1-8
Author(s):  
Lucía Melisa Zini ◽  
Constanza Soledad Carrera ◽  
Elsa Clorinda Lattar ◽  
María Silvia Ferrucci
Keyword(s):  
Pollen Morphology ◽  
Pollen Grains ◽  
Grain Morphology ◽  
Polar View ◽  
Area Index ◽  
Equatorial Diameter ◽  
Polar Index ◽  
Electron Microscopes ◽  
Polar Diameter ◽  
Taxonomic Groups

The pollen grain morphology of Jacaratia corumbensis Kuntze, J. spinosa (Aubl.) A.DC., Vasconcellea quercifolia A. St.-Hil., and Carica papaya L. from Argentine samples were examined for the first time, using light and scanning electron microscopes. Observations and measurements were performed on acetolyzed pollen grains. Principal-components analysis was performed for quantitative morphological variables. Pollen grains were tri-colporate with lalongate endoaperture, oblate spheroidal to prolate, medium, exine bireticulate or reticulate, with a granulate lumina. A fastigium was present. Novel palynological data in this study for species identification revealed the presence of margo in C. papaya and variations in endoaperture shapes in all the species. The endoaperture ends often were H-shaped or horn-shaped. A biplot showed clear separation of the four taxa based on the palynological traits. Vasconcellea quercifolia was strongly correlated with equatorial diameter, equatorial diameter in polar view, exine thickness, and polar diameter, whereas J. corumbensis and J. spinosa were positively correlated with polar index and polar area index, respectively. The distance between two colpi allowed the discrimination of C. papaya. We confirmed the homogenous nature for most of the qualitative palynological characters in Caricaceae, and demonstrated that pollen morphology in combination with statistical analyses is a reliable tool for delimiting taxonomic groups.

DIALLEL ANALYSIS OF THE INHERITANCE OF QUANTITATIVE CHARACTERS IN CABBAGE (BRASSICA OLERACEA L. VAR. CAPITATA L.)

1969 ◽  
Vol 11 (1) ◽  
pp. 103-109 ◽  
Author(s):  
Morgan S. Chiang
Keyword(s):  
Inner Core ◽  
Diallel Analysis ◽  
Diallel Cross ◽  
Effective Factors ◽  
Quantitative Characters ◽  
Equatorial Diameter ◽  
Equal Importance ◽  
Days To Maturity ◽  
Polar Diameter ◽  
Brassica Oleracea L

Additivity of inheritance of length of inner core and days to maturity appeared to be rather important in this diallel cross of cabbage. Equal importance of additivity and dominance was observed in polar diameter and equatorial diameter of cabbage heads. Dominance contributed a large portion of genetic variation in yield while number of wrapper leaves varied with environment. However, there were indications that overdominance was also involved in all characters except polar diameter and days to maturity. The effective factors controlling each character ranged from one to three. The heritability values were high for polar diameter and days to maturity, moderate for number of wrapper leaves and length of inner core, and low for equatorial diameter and yield.

scholarly journals Histology and gametogenesis inHeleobia piscium(Cochliopidae) from the Multiple Use Reserve “Isla Martín García,” Buenos Aires, Argentina

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2548 ◽  
Author(s):  
Stella Maris Martin ◽  
Ana C. Díaz
Keyword(s):  
South America ◽  
Reproductive Cycle ◽  
Buenos Aires ◽  
Rio De La Plata ◽  
Multiple Use ◽  
Río De La Plata ◽  
Early Maturation ◽  
La Plata ◽  
Natural Reserve ◽  
Entre Rios

Heleobia piscium(d’Orbigny, 1835), a member of the Cochliopidae family found only in South America, is distributed from Entre Ríos, Delta del Paraná, and the littoral of the Río de la Plata down as far as to Punta Indio (Buenos Aires), the southernmost limit of the snail’s geographical distribution. To date, little information is available regarding the reproductive cycle of species within this family either in Argentina or throughout South America. The present work analyzed the histology of the reproductive system of the gonochoric speciesH. pisciumand determined the stages oogenesis and spermatogenesis under natural conditions. Specimens ofH. pisciumwere collected in the Multiple-Use Natural Reserve Isla Martín García, located in the Upper Río de la Plata estuary to the south of the mouth of the Uruguay River. The gametogenic cycle in both sexes was found to consist of the following stages: early maturation, maturation, and evacuation. The maturation period was found to extend from January to October and evacuation of the gametes to start in November and end in February (summer in the Southern Hemisphere). The results indicated theH. pisciumexhibit a reproductive cycle without a resting period.

Sign in / Sign up

Export Citation Format

Share Document