PHYTOLITH ANALYSIS OF CYPERACEAE FROM SE BUENOS AIRES PROVINCE, ARGENTINA

FERNÁNDEZ HONAINE, MARIANA; ZUCOL, ALEJANDRO; OSTERRIETH, MARGARITA

Mar del Plata

Otro; 7th International Meeting on phytolith research; 2008

Cyperaceae is one of the main silica accumulator families within the plant kingdom. Conical phytoliths were described by some authors as the most important morphotype in the family, however little is known about the variability and diversity of them, as well as the other morphotypes that are also produced. Since phytoliths are widely used as microfossils, the study of them is essential for the identification of sedge-dominated communities or specific palaeoenvironmental conditions in the fossil phytolith record. Also, silica bodies could be a valuable tool for taxonomic researches within the family. The aim of this study is to describe the phytolith morphotypes of leaves, culms and fruits of some species of Cyperaceae from Pampean region in order to analyse their palaeobotanical and taxonomic relevance. Phytoliths from leaves or culms and fruits of thirteen sedges from Pampean region were extracted by using a calcination technique. Silica content was calculated as dry weight percentage. For each species, at least 200 phytoliths were counted and the relative frequency of each morphotype was calculated. Seven quantitative and three qualitative characteristics were measured on cone shape phytoliths. In order to analyze the taxonomic relevance within the family, cone characters and percentages of phytolith morphotypes were subject to Principal Component Analyses. The values of silica content had a great variability within genera and within species. The results showed that silicification process affected not only epidermal tissue, but also xylem, parenchyma and sclerenchyma. The most abundant morphotype, in almost all the species, is the conical phytolith. Leaf or culm cones have a rounded, rectangular or square base; whereas typical fruit cones have a polygonal base and they are bigger and more robust. The results of the PCA, based on quantitative and qualitative characteristics of cone phytoliths and percentages of phytolith morphotypes, showed some differentiation among genera. The results of this study represent the first values of silica content and the first descriptions of phytoliths from leaves, culms and fruits of the principal sedges of Pampean region.