Analysis of the silicification in Pampas grass (Cortaderia selloana) leaves in individuals developed in different soil types from Pampean Plains, Argentina

FERNÁNDEZ HONAINE, MARIANA; BORRELLI, NATALIA; OSTERRIETH, MARGARITA; DEL RÍO, LUIS

Encuentro; 9th International Meeting on Phytolith Research; 2014

Cortaderia selloana is a native grass from South America and is widely distributed in Argentina. It is usually developed on sandy and wet soils and it is extended on coastal sectors of the Pampean Plains. In many regions of the world this grass is considered an important invasive plant and therefore it has been largely studied in ecological and environmental management researches. Due to its large size, tussock habit and its predominance in many coastal regions, it may be considered as a plant with a relevant role in the biogeochemical cycle of silicon, both as an absorption and deposition source of silicon/amorphous silica biomineralizations from and to the soil system. In order to understand this role in coastal systems it is necessary to first analyze the factors that regulate the silicification process in this species. The aim of this work is to analyze the production and distribution of amorphous silica biomineralizations in leaves from Cortaderia selloana plants grown on different soil types from Buenos Aires Province, Argentina. Plants developed from three different soils were selected and total content of silicophytoliths, obtained from a calcination technique, was analyzed. In order to study the distribution of silicified cells in leaf tissues, samples were clarified and stained with phenol. Also, soil descriptions and soil silica content were carried out through routine techniques. The results showed that Si content in soils varied from 1428,6 to 1873,8 μmol/L, depending on the soil type. Total silicophytolith content of leaves was higher in those plants grown in soils with the highest content of silica; these plants also showed a higher diversity of silicophytolith morphologies. In a same plant, the total content of silicophytoliths varied more between sampling site than between leaf position or age. The percentage of total silicified cells was not different between epidermises, as it was expected. Adaxial epidermis, subjected to a higher solar exposition and thus to a higher transpiration rate do not showed more silicified cells than abaxial (20-30% in adaxial epidermis, 27-31% in abaxial epidermis). This patron may be explained by the anatomy of the leaf, which is characterized by xeromorphic features such as sunken stomata, crypts and hairs, which lower the transpiration rate in those sectors. In general, inferior (older) leaves showed a higher percentage of silicified cells than superior ones. The results obtained showed that the total content of silicophytoliths in this grass is influenced by soil type and silica availability; however the distribution along the same plant depend on their specific anatomical features, the transpiration rate and the age of the organ. Acknowledgments: This work was supported by the Agencia Nacional de Promoción Científica y Tecnológica (PICT-2036/10) and the Universidad Nacional de Mar del Plata (EXA-643/13).