Calcium and silica biomineralizations in leaves of eleven aquatic species of the Pampean Plain, Argentina

Calcium oxalate crystal and silicophytolith assemblages were investigated in leaves of eleven aquatic species from habitats of the Argentinean Pampean Plain. Calcium oxalate druses and raphide bundles mainly occurred in leaf parenchyma and aerenchyma. Druses were observed in Alternanthera philoxeroides, Ludwigia peploides, Polygonum hydropiperoides and Rumex crispus; and raphide bundles in L. peploides and Typha latifolia. No calcium oxalate crystals were observed in Bidens laevis, Mikania parodii, Solanum glaucophyllum, Ranunculus apiifolius or the Juncaceae family. Druse density ranged between 14.62 ± 3.09 (R. crispus) to 39.6 ± 7.2 crystals mm⁻² (P. hydropiperoides), and raphide bundle density ranged between 7.55 ± 1.36 (L. peploides) to 20.55 ± 5.19 crystals mm⁻² (T. latifolia). Silicification mainly occurred in epidermal cells and xylem. Juncus spp., S. glaucophyllum, B. laevis, M. parodii and R. apiifolius produced abundant and diverse phytolith morphotypes. The rest of the species produced very few (L. peploides, P. hydropiperoides, A. philoxeroides) or no identifiable phytoliths (T. latifolia, R. crispus). Silica content ranged from 0.07 (T. latifolia) to 4.7% dry weight (S. glaucophyllum).