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Diatom cells are contained within a unique silica cell wall known as a frustule made up of two valves called thecae, that typically overlap one another. [41] The biogenic silica composing the cell wall is synthesised intracellularly by the polymerisation of silicic acid monomers. This material is then extruded to the cell exterior and added to ...
A frustule is the hard and porous cell wall or external layer of diatoms. The frustule is composed almost purely of silica, made from silicic acid, and is coated with a layer of organic substance, which was referred to in the early literature on diatoms as pectin, a fiber most commonly found in cell walls of plants.
Biogenic silica (bSi), also referred to as opal, biogenic opal, or amorphous opaline silica, forms one of the most widespread biogenic minerals. For example, microscopic particles of silica called phytoliths can be found in grasses and other plants. Silica is an amorphous metalloid oxide formed by complex inorganic polymerization processes.
In mineralogy, silica (silicon dioxide, SiO 2) is usually considered a silicate mineral rather than an oxide mineral. Silica is found in nature as the mineral quartz , and its polymorphs . On Earth, a wide variety of silicate minerals occur in an even wider range of combinations as a result of the processes that have been forming and re-working ...
In more advanced plants, the silica phytoliths (opal phytoliths) are rigid microscopic bodies occurring in the cell; some plants, including rice, need silica for their growth. [8] [9] [10] Silica has been shown to improve plant cell wall strength and structural integrity in some plants. [11]
Secondary walls - especially in grasses - may also contain microscopic silica crystals, which may strengthen the wall and protect it from herbivores. Cell walls in some plant tissues also function as storage deposits for carbohydrates that can be broken down and resorbed to supply the metabolic and growth needs of the plant.
Silica binds to the cellulose in cell walls via hydrogen bonding and forms a kind of template. Additional silica then replaces the cellulose as it decomposes, so that cell walls are often preserved in great detail. [2] Thus silicification begins within the cell walls, and the spaces within and between cells are filled with silica more gradually.
Diatoms are enclosed in protective silica (glass) shells called frustules. They are classified by the shape of these glass cages in which they live, and which they build as they grow. Each frustule is made from two interlocking parts covered with tiny holes through which the diatom exchanges nutrients and wastes. [63]
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