How many types of meristems are present in plants ? Explain them.

Explanation

Meristems are certain specific regions in the plant body concerned mainly with the active cell division. Adjective of meristem is meristematic tissue that includes group or cluster of cells which remain in continuous state of division or retain their power of division.
Depending upon the position in the plant body, meristems are of the following three types :
(A) Apical meristem. It occurs at the growing apices of stem, roots and their branches. These cells are responsible for growth in length of a plant. Formation of primary tissue is mainly due to differentiation of cells derived from apical meristems.
(B) Intercalary meristem. This meristem is located inbetween the regions of permanent tissues. It is believed that some parts of apical meristems are left behind due to tissue differentiation of an organ. These meristems are usually responsible for growth in length of internodes and leaves. They occur at the leaf bases, leaf sheaths of monocots (e.g., grasses), bases of intemodes and below the nodes. The intercalary meristems ultimately disappear and differentiate into permanent tissues
(C) Lateral meristem. These meristems are usually present in the interior of stem and roots in the form of vascular cambium, cork cambium and marginal meristems (in some leaves). Cells of lateral meristem divide mainly in one plane (i.e., periclinal) and cause increase in the diameter of an organ.