Artículos, Informes y presentaciones en Congresos
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Examinando Artículos, Informes y presentaciones en Congresos por Autor "Altamirano, Stella Maris"
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Acceso Abierto Amorphous silica biomineralizations in species from Argentina: content, morphologies and tissue location, systematic and ecological relations(2016) Fernández Honaine, Mariana; Benvenuto, María Laura; Altamirano, Stella Maris; De Rito, Mara Victoria; Osterrieth, MargaritaSilici cation of plants is a widespread process and involves a high amount of plant fami- lies. The study of the content and distribution of amorphous silica biomineralizations in plant tissues has been approached by diverse disciplines, due to the relevance and applications that silicophytoliths have on di erent research areas. The knowledge of the plant production in a speci c area, has multiple applications from anatomical/functional, through ecological up to palaeobotanical and palaeoenvironmental. The present study aimed to compare the content, morphologies and tissue distribution of silicophytoliths in leaves of species from di erent communities of Argentina. We evaluated how silica content varied according to systematic, life cycles (perennials vs annuals), habit (herbs vs arboreals) and status (native vs exotic), and compared with results obtained by other researches. We analyzed at which level the phytolith morphologies can discriminate between plant groups, and which morphologies may be more relevant for taxonomy. Leaves from at least 3 individuals of 92 species, grouped in 26 families, representing some of the main communities of Buenos Aires, Misiones, and Tierra del Fuego provinces, were collected. Silicophytolith were extracted through a calcination technique, and silica content was measured as % dry weight. Silicophytoliths were counted and described under optical microscope following speci c literature. Data of silica content was subjected to Kruskal Wallis and Mann-Whitney tests, depending on the hypothesis eval- uated. Morphology data was subjected to Principal Component Analysis. Fifteen species do not produce silicophytoliths. The silica content ranged between 0.38% (Ranunculus api- ifolius) and 19% (Chusquea ramossisima) and varied according to systematic. However, it was possible to observe that two species of a same genera had di erent behavior (producer and not producer). At family level, the highest media content was observed in Urticaceae and the lowest in Ranunculaceae. Di erences were detected between Poaceae vs Asteraceae, Juncaceae, Rosaceae and Solanaceae (p< 0.01). Within Poaceae, Asteraceae and Cyperaceae families, no silica content di erences were detected among species. There were no statistical di erences between annuals and perennials, and natives and exotics (except within Poaceae family), contrary to what it was reported previously by other researchers. Leaf content in herbs was higher than in trees and shrubs (p< 0.01); however, the families with higher silica accumulation are mostly herbaceous (grasses, sedges). The main silici ed tissue is epidermis, but also xylem and parenchyma became silici ed. PCA showed that it is possible to di er- entiate some families based on their phytolith assemblages. Poaceae (short cell phytoliths), Cyperaceae (cone shaped phytoliths), Urticaceae, Moraceae and Cannabaceae (cystoliths) are clearly di erentiated from other groups. The redundancy of some morphologies such as tabular polygonal (derived from epidermis) and cylindrical sulcate xylem, makes di cult the discrimination of some groups. Finally, a detailed morphometric study will probably allow some additional di erentiation, also within the groups already di erentiated. However, be- sides the diagnostic character of the phytolith morphologies of a speci c taxa, it is relevant to increase our knowledge about the distribution of the silici cation process among plants, not only for palaeobotanical but also for anatomical, physiological and ecological purposes. - Resumen
Acceso Abierto Calcium oxalate crystal production in different plant communities of the Pampean Plain: a comparative analysis.(2016) Fernández Honaine, Mariana; Altamirano, Stella Maris; Borrelli, Natalia L.; Benvenuto, María Laura; Osterrieth, MargaritaCalcium oxalate crystals (COC) are the most prevalent and widely distributed mineral de-posits throughout the families of higher plants. COC were analyzed in vegetative organs andfruits of 13 species from dierent plant communities of the Pampean Plain: forests (Acacia melanoxylon, Celtis ehrenbergiana, Eucalyptus globulus), agroecosystems (Glycine max), andwetlands (Alternanthera philoxeroides, Bidens laevis, Hydrocotyle bonariensis, Ludwigia pe-ploides, Mikania parodii, Polygonum hydropiperoides, Ranunculus apiifolius, Rumex crispusand Typha latifolia). Organs were placed in an ultrasound bath and washed with distilled wa-ter to remove possible mineral contaminants. Afterwards, diaphanization, clearing of tissues with 50% sodium hypochlorite and cross sectioning were realized. The material was mounted with gelatin-glycerin and COC were identied and described with optical, polarization and scanning electron microscopes. Crystal density was calculated and the composition of the crystals was analyzed by X-ray dispersive spectroscopy (EDS). Statistical analyses (Kruskal-Wallis test and Principal Component Analysis) were made in order to compare COC size and production between communities, species and organs. Druses were observed in C. ehrenber-giana, E. globulus, A. philoxeroides, H. bonariensis, L. peploides, P. hydropiperoides, and R.crispus. Raphide bundles were present in L. peploides and T. latifolia; and prismatic crystalsin A. melanoxylon, E. globulus, H. bonariensis, L. peploides and R. crispus. Calcicationmainly occurred in parenchymatous tissue. No COC were observed in B. laevis, M. parodiiand R. apiifolius. A single crystal morphology was observed per organ, except in leaves ofL. peploides and E. globulus, which present both druses and raphides, or druses and prismatic crystals, respectively. In fruits, only prismatic crystals were observed independently of the morphology produced in the vegetative organs. The species analyzed had signicant differences in the size of the COC (H: 443.5, p< 0.001). Particularly, some aquatic species(A. philoxeroides, L. peploides, P. hydropiperoides and R. crispus), given the great size oftheir druses (36-58m), could not be differentiated among them (p> 0.05). Consideringeach species, the fruits had smaller COC (5-11m) than the vegetative organs (14-210m,p< 0.001). The COC density was signicantly dierent between communities, species andorgans, and allowed to distinguish the community and the organs with greater productionof COC. Thus, the tree species were grouped together with the fruits of the species analyzedgiven their greater COC density: 9167-28308 and 1112-18531 crystals/mm2, respectively. Inside this group, C. ehrenbergiana and E. globulus have more anity because they produce druses, unlike A. melanoxylon and the fruits analyzed that produce prismatic crystals. It was not possible to discriminate between the aquatic community (7-250 crystals/mm2) and thecrop (340 crystals/mm2). The description and quantification of COC allowed to distinguish among different plant communities, species and organs. The fruits showed the smallest size and the highest density of crystals. This particular pattern ensures the normal growth and development of the embryos, since crystals act as a calcium source, prevent damage frominsects and allow reproductive success of the species. - Resumen
Acceso Abierto Silicophytoliths and taphonomy in Cenozoic pedostratigraphic sequences of the Pampean Plain, Argentina(2016) Osterrieth, Margarita; Borrelli, Natalia L.; Benvenuto, María Laura; Fernández Honaine, Mariana; Frayssinet, Celia; Altamirano, Stella Maris; De Rito, Mara Victoria; Donna, Roberto; Paolicchi, Micaela; Álvarez, María FernandaGrasslands and savannas occupy one forth of the total surface of South America continent, and within it, the Pampean plain region, located in the central area of eastern Argentina, covers an area of 1,200,000 km2. The dominant soils are Mollisolls generally deep, developed from well-drained loessic parental material and characterized by a silty-loam texture. Pampean Plains is one of the most fertile regions of the world. Intense agricultural activities are carried out there and this, in turn, has strongly modified the native plant communities, especially grasslands. Depending on the environmental and pedological conditions, silicophytoliths are affected by diverse taphonomical processes, both in natural and anthropic environments. They can be preserved, dissolved or fragmented, and also be transported by different agents (wind, water, animals and people). Other taphonomical aspects also important to evaluate are the methodologies used in silicophytolith studies, from soil sampling to studies at a submicroscopic level. There are several current methodologies and the work is essentially done at a very detailed resolution level, which could lead to interpretation errors if the environmental or paleoenvironmental context of the study material is unknown or not clearly stated. The study area is located in regional geomorphological units from Pampean Plain, Argentina, and integrated profiles representative of typical pedoestratigraphic sequences were analyzed. Silicophytoliths were analyzed as part of the whole mineralogy of the soil samples and morphologies were described under optical and scanning electron microscopes. The results show high amounts of silicophytoliths which have been affected by various physical and chemical alteration and/or by taphonomic processes of different types and degrees of intensity. The percentage and number of silicophytoliths per gram of soil vary. In superficial horizons (O, A), the percentage ranged between 10-65%, with 11.000.000-30.000.000 phytoliths per gram of soil (n/g.s). In subsuperficial horizons (AC, B, BC) between 2-6% and 1.000.000-5.000.000 silicophytoliths n/g.s were observed. The percentage of silicophytoliths in loessic parent material (C) ranges between 0.4-2%, with 500.000-2.000.000 n/g.s. In paleosols, percentages range between 1-8%, and the number of silicophytoliths per gram of soils were 1.500.000-8.000.000. Silica and silicophytolith biomass content per ha of soil varied according C biomass, in the pedostratigraphic Cenozoic sequences from Pampean plains. Our data show that the content of silicophytoliths decreases between 50 and 95% from superficial to subsuperficial soil horizons due to pedological processes. The comprehension of the physico-chemical degradation and transference processes within silicophytolith-plant-soil-environment system is essential in order to evaluate the role of taphonomical processes in the biogeochemical cycle of silicon. Finally, it is proposed that the displacement of native grasslands may be bio-physico-chemically balanced by the introduction of crops, in relation to the silicon cycle, since they are also important silicophytolith producers in the SE Pampean agroecosystems. Acknowledgments: This work was supported by PICT 1583/2013 AGENCIA and EXA 741/15-UNMDP.