Phytolith analysis of Cyperaceae from SE Buenos Aires Province, Argentina

FERNÁNDEZ HONAINE M., ; ZUCOL A. ; M. OSTERRIETH.

Mar del Plata

Encuentro; 7th IMPR – 4th SMPR; 2010

SPR

Cyperaceae is one of the main silica accumulatorfamilies within the plant kingdom. Conicalphytoliths were described by some authors as themost important morphotype in the family, howeverlittle is known about the variability and diversity ofthem, as well as the other morphotypes that are alsoproduced. Since phytoliths are widely used asmicrofossils, the study of them is essential for theidentification of sedge-dominated communities orspecific palaeoenvironmental conditions in the fossilphytolith record. Also, silica bodies could be avaluable tool for taxonomic research within thefamily. The aim of this study is to describe thephytolith morphotypes of leaves, culms and fruits ofsome species of Cyperaceae from Pampean regionin order to analyse their palaeobotanical andtaxonomic relevance. Phytoliths from leaves orculms and fruits of thirteen sedges from Pampeanregion were extracted by using a calcinationtechnique. Silica content was calculated as dryweight percentage. For each species, at least 200phytoliths were counted and the relative frequencyof each morphotype was calculated. Sevenquantitative and three qualitative characteristicswere measured on cone shape phytoliths. In order toanalyze the taxonomic relevance within the family,cone characters and percentages of phytolithmorphotypes were subject to Principal ComponentAnalyses. The values of silica content had a greatvariability within genera and within species. Theresults showed that silicification process affectednot only epidermal tissue, but also xylem,parenchyma and sclerenchyma. The most abundantmorphotype, in almost all the species, is the conicalphytolith. Leaf or culm cones have a rounded,rectangular or square base; whereas typical fruitcones have a polygonal base and they are bigger andmore robust. The results of the PCA, based onquantitative and qualitative characteristics of conephytoliths and percentages of phytolithmorphotypes, showed some differentiation amonggenera. The results of this study represent the firstvalues of silica content and the first descriptions ofphytoliths from leaves, culms and fruits of theprincipal sedges of Pampean region.