PHYTOLITH ANALYSIS OF SPECIES OF AQUATIC HABITATS FROM SE BUENOS AIRES PROVINCE, ARGENTINA

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

Mar del Plata

Otro; 7th International Meeting on phytolith research; 2008

The most frequent species associated with aquatic habitats in Argentina belong to Typhaceae, Cyperaceae, Juncaceae, Apiaceae and Polygonaceae families, and certain species of Poaceae, among others. Cyperaceae, along with Poaceae, are the main silica producers in plant kingdom. However, the phytolith production of these characteristic aquatic habitat families is scarcely known. The knowledge of their qualitative and quantitative phytolith production would allow the identification of these plant communities as well as particular palaeoenvironmental characteristics in the fossil phytolith records. In order to describe the phytolith assemblages of some of the main species growing in ponds, lagoons and/or aquatic habitats from SE Buenos Aires province (Argentina) we selected thirteen species. Eight families were represented: Amaranthaceae (1 sp.), Apiaceae (1 sp.), Asteraceae (2 spp.), Juncaceae (4 spp.), Onagraceae (1 sp.), Polygonaceae (2 spp.), Solanaceae (1 sp.) and Typhaceae (1 sp.). Phytoliths from leaves were extracted following a calcination technique and silica content was calculated as dry weight percentage. Juncus spp., Solanum glaucophyllum, Bidens laevis and Mikania parodii produced abundant and diverse morphotypes. The rest of the species produced very scarce (such as Ludwigia peploides, Polygonum hydropiperoides, Alternanthera philoxeroides,) or did not produce identificable phytoliths (such as Typha latifolia, Rumex crispus, Hydrocotyle sp.). Silica content ranged between 0.23 (Juncus sp.) to 2.71% (Mikania parodii). Articulated and isolated cylindrical sulcate tracheid phytoliths and parallelepipedal psilate phytoliths, probably derived from epidermal tissue, were the only morphotypes observed in the species with scarce production. Phytolith assemblages of the species with abundant production were characterized by cylindrical sulcate tracheids, stomatal complexes, elongate psilate phytoliths (Juncus spp.), tabular lobate epidermal cells (B. laevis), parallelepipedal psilate epidermal cells (S. glaucophyllum, M. parodii), silica skeletons composed by isodiametric cells (S. glaucophyllum), silicifications of multicelullar hairs (M. parodii and B. laevis) and silica skeletons composed by diverse morphotypes. The results showed that silicification process mainly occurred in epidermal cells, trichomes and xylem. These descriptions of leaf phytolith assemblages represent the first contribution to the phytolith analysis of these taxa. Finally, they were compared with the phytolith studies carried on the same families by other authors.