write a short note on different types of meristematic tissues
Answers
Meristematic tissues are a group of young cells that are in a continuous state of division.
i) They are living and thin walled
(ii) Vacuoles are few and small in size
(iii) The cells contain a dense protoplasm and conspicuous nuclei
(iv) The cells are spherical, oval or polygonal in shape
4 Types of Meristematic Tissues and their Functions
Meristematic tissues are a group of young cells that are in a continuousstate of division.
These tissues are mostly found at the apices of root and shoot.
The main characteristics of cells of meristematic tissues
(i) They are living and thin walled
(ii) Vacuoles are few and small in size
(iii) The cells contain a dense protoplasm and conspicuous nuclei
(iv) The cells are spherical, oval or polygonal in shape
(v) They do not store reserve food material and are in an active state of metabolism.
Types of Meristems:
I. Classification based on origin and development:
On the basis of origin and development of initiating cells, meristems can be divided into three types:
(i) Promeristem or priordial meristem:
A group of young meristematic cells of a growing organ. It is the early embryonic meristem from which other advanced meristems are derived. In a plant, it occupies a small area at the tip of stem and root. It further divides to form primary meristem.
(ii) Primary meristem:
These are derived from promeristem. They are present below the promeristem at shoot and root apices. These cells divide and form permanent tissues.
(iii) Secondary meristem:
It is derived from primary permanent tissues which have the capacity of division e.g. Cork-cambium, cambium of roots and inter fascicular cambium of stem. II. Classification on basis of position:
On the basis of their position in the plant body, meristems are of three types
(i) Apical meristem: These are found at the apices or growing points of root and shoot and bring about increase in length. It includes both pro-meristem as well as primary meristem
(ii) Intercalary meristem: It lies between the region of permanent tissues and is considered| as a part of primary meristem which has become detached due to formation of intermediate permanent tissues. It is found either at the base of leaf e.g. Pinus or at the base of internodes e.g. grasses.
(iii) Lateral Meristem: These are arranged parallel to the sides of origin and normally divide periclinally or radially and give rise to secondary permanent tissues. These increase the thickness of the plant part.