Question

Cystolith contains
A.$CaCO_{3}$
B.$CaCl_{2}$
C.$MgCl_{2}$
D.$CaO$

Answer 1

Hint: Cystoliths means the deposition of calcium carbonate in the epidermal cells of leaves of the plants in the genus Acanthaceae and Urticaceae.

Complete answer:
 Cystolith is a term which is used for describing the outgrowths of the epidermal cell wall, normally the calcium carbonate formed in a cellulose matrix in special cells called lithocysts, usually in the leaf of plants.
Cystoliths are seen in certain families including in a lot of genera of Acanthaceae. Plants in the family Urticaceae generally known as stinging nettles, also form leaf cystoliths but only through their later flowering and seed setting stages. Further examples include Cannabis and other plants in the family Cannabaceae, which produce leaf and flower cystoliths, and the Ficus elastica, the Indian rubber plant of the family Moraceae.

The cystolith is a spindle shaped body composed of concentric layers of longitudinally oriented cellulose microfibrils connected with pectins and other cell wall polysaccharides. At the time of maturity it is heavily impregnated with calcium carbonate. Various cystoliths also include silicon and are covered in a sheath of siliceous material. Cystolith arrangement occurs at the tip of a peg that grows in from the lithocyst wall. Facts from ultrastructure gives an idea that the lithocyst cytoplasm transports carbohydrates to the cystolith via Golgi vesicles, and organizes the deposition of cystolith cellulose microfibrils through a system of microtubules lying underneath the plasma membrane that covers the growing cystolith. The peg is a collection of heavily staining amorphous compounds like that of an apoplastically sealed cell wall. It is unable to support the migration of lanthanum ions into the cystolith. Minerals crystals are also found in plant cell walls in the type of calcium oxalate, carbonate or silica.

Hence, the correct answer is option (A)

Note: They are generally visible as dots or variously shaped marks especially in dried leaves. They serve as some kind of protection from the leaf eating insects or other animals.