Question

Cystolith is the crystal of
(a) Calcium oxalate
(b) Calcium carbonate
(c) Calcium pectinate
(d) Magnesium sulfate

Answer 1

Hint:Cystolith refers to the outgrowth of cell walls of some kind of specialized cells known as lithocysts, present in the leaves. It is used as a source of calcium in order to regulate the calcium level in plants.

Complete answer:
Cystolith is made up of calcium carbonate that is also known as calcite or lime. The cystolith is typically a spindle-shaped structure consisting of longitudinal microfibrils, pectins, and cell wall polysaccharides arranged in concentric circles. Upon maturity, it gets embedded with crystals of calcium carbonate. It helps in the regulation of calcium levels in the plant. It is the characteristic feature of families of Acanthaceae, Urticaceae, and is generally formed in the late-flowering stage or seed setting stage.
- It can also be seen in the flowers of the cannabis plant of the family Cannabaceae and Indian rubber plant Ficus elastica of the family Moraceae.
- The tip of the peg attached to the lithocyst wall gives rise to the cystolith.
- The Golgi apparatus present in the cytoplasm of the lithocysts transports the cellulosic microfibrils to the cystolith with the help of a network of microtubules.
- The calcium oxalate crystals are present in the vacuoles of idioblast cells. It maintains the calcium balance in the body and also prevents it from being grazed upon by the cattle.
So, the correct answer is ‘Calcium carbonate'.

Note:
- Some cystolith crystals can also get impregnated with silica and get covered by a siliceous sheath.
- Raphides are another group of crystals consisting of either calcium oxalate monohydrate (prismatic crystals) or calcium carbonate in the form of aragonite (dipyramidal orthorhombic crystals). They are generally present in the parenchymatous cells of mesophyll.