Question

write the function of Meristem on the basic of position in the plant body?

Answer 1

Lateral meristem -- increases the girth of the plant.present at sides

intercalary meristem -- it is the base of the growth of the branches.present at sides 

apical meristem -- present at the tip of roots stem and branches.helps in growth .....

hope helps you.

Answer 2

II. Classification on basis of position:

On the basis of their position in the plant body, meristems are of three types (Fig. 3.1)

Schematic represention of position of different meristems

(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.

Several theories have been put forward to explain the activity of apical meristem:

Apical cell theory:

The theory was first proposed by Hofmeister (1857) and advanced by Nageli (1878). According to this theory, a single apical cell is the structural and functional unit of apical meristem which governs the entire process of apical growth. However, such organization has been found only in cryptogams.

Histogen cell theory:

This theory was given by Hanstein (1868). According to this theory root and shoot apices consists of the central or inner mass called Plerome surrounded by the middle region composed of isodiametric cells called periblem and the outermost uniseriate layer of Dermatogen. Dermatogen gives rise to epidermis, periblem to cortex and endodermis and plerome to vascular bundle and pith. These three layers were called Histogen by Hanstein.

Tunica-corpus theory:

This theory was proposed by Schmidt (1924). According to this theory, mass of dividing cells are of two types: Tunica, the outer consisting of one position of different meristems or more peripheral layers of cells, forming the outer region and Corpus, the central undifferentiated multilayered mass of cell. Epidermis is derived from outer layer of tunica and other tissues from remaining layer of tunica and corpus.

(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.