Question

Complementary cells occur in
(A) Pericycle
(B) Pith
(C) Lenticels
(D) Endodermis

Answer 1

The ground tissue system is clearly differentiated into various zones. In the transverse section of all dicot stems, monocot roots and dicot roots; the ground tissue exhibits clear zonation into an outer cortex and central pith. In between cortex and pith various other tissues are present. Such differentiation is not present in the monocot stems.

Complete answer:
Lenticel: It is a small portion of periderm which is produced due to the activity of phellogen. The phellogen (cork cambium) is a meristematic tissue that develops during the secondary growth and normally produces suberized cork cells on the outer side.
But, when the activity of phellogen increases at a certain point than elsewhere, then it starts producing loosely-arranged, thin-walled parenchymatous cells with numerous intercellular spaces, instead of thick- walled suberized cork cells. These thin-walled cells, which are now produced instead of thick-walled cork cells, are called complementary cells.
Now let us match this with given options:-
Pericycle :- this is the outermost region of the stele. It has thick walled sclerenchymatous cells and thin walled parenchymatous cells. Thus this option is not correct.
Pith:- It is also called medulla. It occupies the central part in dicot stems, dicot roots and monocot roots. In monocot stems, pith cannot be distinguished as vascular bundles are present throughout the stem. Pith is generally composed of large parenchymatous cells. Thus this option is not correct.
Lenticels :- when the activity of phellogen increases at a certain point than elsewhere, then it starts producing loosely-arranged, thin-walled parenchymatous cells that are called complementary cells . Thus this option is correct.
Endodermis :- innermost layer of cortex is usually called endodermis. It consists of barrel shaped or oval shaped cells which are parenchymatous and they are not complementary.

Our required answer is C) Lenticels.

Note: As the number of complementary cells increases, it creates pressure on the epidermis which soon results in the rupture of epidermal cells. The small openings which are formed due to rupture in the epidermis are called lenticels.
Lenticels are the lens-shaped openings present on the bark that serve for exchange of gases between the internal tissue of the stem and the outer atmosphere. They occur in most woody trees.