Phytoliths of Indian grasses and their potential use in identification

Phytoliths are amorphous silicon dioxide (SiO2. nH(2)O) inclusions abundant in leaves, internodes and glumes in members of Poaceae. They may occur as inclusions filling the entire lumen of the silica cells, bulliform cells an d trichomes or may be part of the outer epidermal cell walls. Since phytoli ths are resistant to fungal or animal digestive juices, a large quantity of phytoliths accumulate in the soil where grasses grow. Compared with the po llen grains of grasses which tend to be uniform, phytoliths vary in size an d morphology and can be of value in identification at different taxonomic l evels and in the dating of past vegetation. The size and shape of phytolith s of about 100 species of grasses from Tamil Nadu, India, have been determi ned. Silica bodies were observed either after isolation or in cleared leaf blades. Size and shape of phytoliths were determined under a microscope or from micrographs of the specimens. Size and shape can be used to assign the phytoliths to their respective subfamilies and to distinguish some of the grasses at the generic level. Drawings of silica cells and an identificatio n key are provided for 80 species. (C) 2000 The Linnean Society of London.