Collenchyma Tissue: Types, Characteristics & Functions

Collenchyma is a plant tissue composed of living cells with thickened cell walls. It is one of the three main types of ground tissues found in plants, along with parenchyma and sclerenchyma. Collenchyma cells provide mechanical support to the growing parts of plants, such as young stems, petioles (leaf stalks), and the outer layers of leaf veins. The primary function of collenchyma is to provide flexibility and strength to the plant.

What is Collenchyma?

Collenchyma is a type of plant tissue composed of elongated living cells that provide mechanical support and flexibility to plants. It is a sub-type of simple permanent tissue. Plant tissue refers to a group of cells with a common origin and structure that are organized to perform common functions within the plant body. Plant tissues can be classified into two main categories: Meristematic tissue and Permanent tissue. Permanent tissue is further classified into simple permanent tissue and complex permanent tissue. Simple permanent tissue is further subdivided into parenchyma, collenchyma, and sclerenchyma.

Characteristics of Collenchyma

• It is typically located between the cortex of the stem and the endodermis of its vascular bundles.
• Collenchyma consists of living cells.
• Shapes of the cells are elongated, oval, spherical, or polygonal.
• Collenchyma cells contain an unevenly thickened primary cell wall.
• The intercellular spaces are small.
• Collenchyma can expand radially and tangentially on absorbing water due to their weak lignified cell walls.
• It contains chloroplasts for food storage.
• During the secondary growth of the plant, collenchyma tissues get crushed.

👁 Collenchyma-cells

Types of collenchyma

Based on the thickening of the cell wall, collenchyma is divided into 4 types:

• Lacunar Collenchyma: Lacunar Collenchyma contains intercellular spaces, and thickening is more around these spaces.
• Angular Collenchyma: In this type, the thickening occurs at the corners of the cells, giving them a distinct angular appearance. It is the most common collenchyma tissue.
• Annular collenchyma: In annular collenchyma, the cell wall is uniformly thickened.
• Lamellar Collenchyma: Lamellar Collenchyma cells have continuous layers of thickening in their cell walls. The cell walls are unevenly thickened, with the thickest regions forming these layers.

What are Collenchyma Cells made of?

Collenchyma cells are primarily composed of cellulose and pectin. Cellulose provides strength and rigidity. It has the capacity to store water and can expand by up to 200% when they absorb water. Pectin contributes to the gel-like consistency of the cell wall matrix and provides flexibility. Collenchyma cell walls may also contain hemicellulose, which helps to reinforce the cell wall structure. Collenchyma cells are primarily located on the outer surface of roots and stem in plants, as they continuously grow in plants.

Function of cell: Cells play a significant role in supporting other tissues and facilitating water absorption, thereby enabling plant growth. The thickening of the cell walls is irregular, often occur in the corners or localized regions of the cells, and helps reduce mechanical stress on the plant.

Functions of Collenchyma

Collenchyma tissue plays an important role in the growth of plants, contributing to their overall form, support, and adaptation to environmental conditions. The various functions performed by collenchyma tissue are as follows:

• Mechanical Support: One of the primary functions of collenchyma is to provide mechanical support to the growing plant. The thickened cell walls of collenchyma cells provide strength and rigidity, allowing them to withstand mechanical stresses such as bending and stretching.
• Flexibility: While providing support, collenchyma tissue also retains flexibility. The living nature of collenchyma cells and the arrangement of their cell walls allow for bending and movement without causing damage to the plant.
• Nutrient Storage: Collenchyma cells can store nutrients, such as starch and lipids, within their living protoplasts.
• Tissue Repair: When plant tissues are damaged, collenchyma cells undergo division and differentiation for tissue repair and wound healing.
• Defense Mechanism: Collenchyma cells can also participate in defense responses against pathogens and mechanical stresses.

Significance of Collenchyma

Collenchyma tissue actively contributes to the growth and development of plant organs. Its significance lies in its role as a supportive and flexible tissue, contributing to mechanical stability, nutrient transport, and metabolic activities. It ensures the overall functionality, survival, and adaptability of the plant to its environment.