Define Meristematic tissue. Classify the types …

Meristematic tissue is the plant tissue that has the ability to divide actively throughout its life.

The meristematic tissue is of the following types:

Meristematic Tissue On the basis of Origin

Promeristem

• The earliest and youngest meristematic tissue.

• It originates from the embryo.

• The primary meristem arises from the promeristem.

• It is found in the root and the shoot tips.

Primary Meristem

• It arises from the promeristem.

• Cells divide actively.

• It is present below the promeristem and forms the permanent tissue.

Secondary Meristem

• It originates from the primary meristem.

• The permanent tissue forms from the secondary meristem.

Meristematic Tissue On the Basis of Position

Apical Meristem

• These are present at the tips of the roots and shoots and helps in the increase of the height of the plants.

• Various cell divisions facilitate the growth of the cells in the roots and shoots and help in cellular enlargement.

• Apical meristem is divided into-promeristem zone, which contains actively dividing cells, and the meristematic zone, which contains protoderm, procambium and ground meristem.

Intercalary Meristem

• It is located in the leaves and internodes at the intercalary position.

• These help to increase the length of the internode.

• It is found in grass, monocots and pines.

• It is a part of apical meristem and adds to the height of the plant.

Lateral Meristem

• It is located in the stems and roots on the lateral side.

• It increases the thickness of the plant.

• Vascular cambium and cork cambium are the two lateral meristems.

• These divide preclinically or radially and give rise to secondary permanent tissues.

Meristematic Tissue On the Basis of Function

Protoderm

• It is the outermost plant tissue and forms the epidermis.

• It protects the plants from any mechanical shocks.

Procambium

• It is the innermost tissue and gives rise to xylem and phloem.

• It helps in the transport of water and nutrients to different parts of the plant.

Ground Meristem

• The cells are large with thick walls.

• It forms the cortex, pericycle and pith.