Meristematic Tissue: Definition, Types, Diagram and Functions

Meristematic tissue is a specialised plant tissue composed of actively dividing cells that give rise to all other tissues and organs in a plant. These dynamic cells are found in specific regions, ensuring continuous growth in both length and girth. Understanding what is meristematic tissue not only reveals how plants grow but also highlights their remarkable regenerative capability.

Also Read: Plant Cells

Characteristics of Meristematic Tissue

The characteristics of meristematic tissue are central to its role in plant growth and development:

1. Actively Dividing Cells: Cells in meristematic tissue remain in a perpetual state of division, enabling the constant production of new cells.

2. Thin Cell Walls: Their cell walls are generally thin and flexible to facilitate rapid growth.

3. Prominent Nucleus: Each meristematic cell typically contains a single large nucleus that governs cell division.

4. Minimal Vacuoles: Vacuoles, if present, are small and few, ensuring the cells dedicate most of their cytoplasm to active division.

5. Dense Protoplasm: Because these cells are metabolically highly active, their cytoplasm is dense.

6. No Intercellular Spaces: The cells are tightly packed, leaving little to no space between them.

7. Healing and Regeneration: By rapidly producing new cells, meristematic tissue assists in wound repair within the plant.

These characteristics of meristematic tissue collectively ensure uninterrupted growth and the formation of new structures such as leaves, buds, and flowers.

Meristematic Tissue Diagram

To visualise the distribution of these tissues, a meristematic tissue diagram often highlights the apical meristem at the tips, the intercalary meristem in the internodes, and the lateral meristem along the circumference of stems and roots. 

Meristematic Tissue Function

The meristematic tissue function is primarily to produce new cells that differentiate into various specialised tissues. As these cells proliferate, they contribute to:

• Primary Growth: Increase in the length or height of a plant, particularly at the tips of roots and shoots.

• Secondary Growth: Expansion in thickness or girth, often seen in woody plants and stems.

• Regeneration: Replacement of damaged tissues and healing of injuries.

• Formation of Permanent Tissues: Meristematic cells eventually develop into mature tissues like the xylem, phloem, cortex, or epidermis.

By consistently replenishing the plant with fresh cells, this tissue ensures the plant’s ongoing development and adaptability.

Types of Meristematic Tissue

When exploring the types of meristematic tissue, it is helpful to classify them based on origin and location within the plant. Each classification reflects a distinct role in the plant’s growth pattern.

A. Based on Origin

1. Promeristem

• The earliest stage of meristematic cells originates directly from the embryonic tissues.

• Gives rise to the primary meristem.

• Commonly found in the apical regions of roots and shoots.

2. Primary Meristem

• Develops from the pro meristem.

• Actively divides to promote the formation of primary tissues.

• Responsible for the initial growth in length (primary growth).

3. Secondary Meristem

• Originates from cells that were once part of the primary meristem but later became capable of dividing again.

• Contributes to secondary growth, increasing the plant’s girth (e.g., vascular cambium).

B. Based on Position

1. Apical Meristematic Tissue

• Localised at the tips of roots and shoots.

• Facilitates an increase in the height of the plant through rapid cell division.

• Divided into the pro meristem (actively dividing cells) and zones containing protoderm, procambium, and ground meristem.

2. Intercalary Meristem

• Located at the bases of leaves and internodes, particularly in grasses and some monocots.

• Helps elongate the internodes, thus contributing to plant height when the apical meristem is at a distance.

• Plays a key role in rapid regeneration in grazed or mown plants.

3. Lateral Meristem

• Found along the lateral sides of stems and roots.

• Increases the thickness of the plant, contributing to secondary growth.

• Includes vascular cambium and cork cambium, both essential for the thickening of stems and roots.

C. Based on Function

1. Protoderm

• The outermost layer eventually forms the epidermis.

• Protects plants from mechanical injury and regulates gas exchange.

2. Procambium

• Forms the vascular tissues—xylem and phloem.

• Ensures transport of water, minerals, and sugars throughout the plant.

3. Ground Meristem

• Gives rise to the ground tissues, such as the cortex and pith.

• These cells have thicker walls and may store food or provide structural support.

Quick Quiz

Q1: Which meristem is responsible for increasing the girth of a plant?

Q2: Where is apical meristematic tissue located?

Q3: State two characteristics of meristematic tissue.

Q4: Name the types of meristematic tissue based on their location.

Answers:

A1: Lateral Meristem

A2: At the tips of roots and shoots

A3: Answers may vary (e.g., actively dividing cells, thin cell walls)

A4: Apical, Intercalary, and Lateral meristems

These extra tools can help students better memorise and understand the core concepts surrounding meristematic tissue.

For more insights on plant anatomy and growth, explore the-

• Plant Tissue System

• Shoot and Stem

• Cell Division