Phytoliths: Persistence & Release of Silicon in Soil and Plants – A Review
A. Senthilkumar *
Department of Soils and Environment, Agricultural College and Research Institute, Madurai-625 104, India.
B. Bhakiyathu saliha
Department of Soil Science & Agricultural Chemistry, Agricultural College and Research Institute, Killikulam, Thoothukudi dt-628 252, India.
P. Saravana Pandian
Department of Soils and Environment, Agricultural College and Research Institute, Madurai-625 104, India.
R. Thamizh vendan
Department of Agricultural Microbiology, Agricultural College and Research Institute, Madurai-625 104, India.
A. Gurusamy
Dryland Agricultural Research Station, Tamil Nadu Agricultural University, Chettinad-630 102, Sivagangai District, India.
P. P. Mahendran
Department of Soils and Environment, Agricultural College and Research Institute, Madurai-625 104, India.
*Author to whom correspondence should be addressed.
Abstract
Phytoliths are formed from silica carried up from groundwater and some plants. The weathering of silicate minerals at the Earth’s surface provides large amounts of soluble silica, some of which is absorbed by growing plants. In solution, silica exists as mono silicic acid Si (OH4) with pH values of 2–9. It is carried upward in the vascular system and becomes concentrated during transpiration around the leaf stomata. The supersaturated solution begins to polymerize or gel then solidifies and forms solid opaline silica (SiO2:nH2O) bodies (phytoliths) within and between some of the plant cells. Phytoliths were extracted from the 7.4 meter loess core and analyzed morphologically and isotopically from the occluded carbon. Rates of isotopic fractionation between plant and phytolith were determined by measurements from many modern tree, fern, and grass species. The use of phytolith biochar as a Si fertilizer offers the undeniable potential to mitigate desilication and to enhance Si ecological services due to soil weathering and biomass removal. Silicon is accumulated at levels equal to or greater than essential nutrients in plant species belonging to the families Poaceae, Equisetaceae, and Cyperaceae. However, the abundance of silicon in soils is not an indication that sufficient supplies of soluble silicon are available for plant uptake.
Keywords: Phytoliths, formation, morphology, carbon sequestration, silicon in soil and plants