Meristematic Tissue

The term meristem was given by Carl Wilhelm von Nägeli. Meristematic tissues contain undifferentiated cells which are the building blocks of the specialized plant structures. These cells are present in the zone called meristem and can divide actively.

Meristematic tissues contain living cells with varied shapes. They possess a large nucleus devoid of the vacuole. The cells have no intercellular space. The size of the cells is very small and can divide effectively.

Meristematic Tissue

Characteristics of Meristematic Tissue

The characteristics of meristematic tissue are as follows:

  1. The cells of the meristematic tissue are commonly called meristems.

  2. The cells of the meristematic tissue have the quality of self-renewal. Every time the cell divides, one cell remains identical to the parent cell and the others form specialized structures.

  3. They have very small and few vacuoles.

  4. They are living and thin-walled.

  5. The protoplasm of the cells is very dense.

  6. The meristematic cells heal the wounds of an injured plant.

  7. The cells of the meristematic tissues are young and immature.

  8. The cells do not store food.

  9. They exhibit a very high metabolic activity.

  10. They possess a single, large and prominent nucleus.

Types of Meristematic Tissue

The meristematic tissues are of the following types:

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.

On the Basis of Position

Apical Meristem

  • These are present at the tips of the roots and shoots and help in the increase in 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 periclinically or radially and give rise to secondary permanent tissues.

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.

The meristematic tissues are usually found in the apices of the root systems and the shoots and are in a continuous state of division.

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