Collenchyma

Definition Of Collenchyma

Collenchyma cells are plant cells that have unequally thick primary cell walls which provide principally mechanical support and some degree of flexibility. They primarily occur below the stem and the skin of the leaves. These cells make it certain that plants can withstand mechanical pressure and grow erect.

Collenchyma provides the growing tissues of a plant with support, specifically those of a requirement for strength and flexibility. It provides structural support for young stems and leaf veins of a plant such that the plant can bend without breaking. This, in turn, ensures the support of the plant as it grows and accords itself to the surrounding environment.

Structure Of Collenchyma

The structure of collenchyma is given below:

Cell Structure And Composition

Collenchyma cells have an irregular shape with some living cells containing a protoplast and living only for short periods. They have unevenly thickened primary cell walls.

Compared to sclerenchyma cells, the walls of collenchyma cells are thin, and they can even be a bit pliable. These cells provide support to the plant. They are found in growing regions within the plant and in parts of the plant that are still elongating. The best examples of this type of cell are cells that originate from plants. Growth of the plant causes the cell to stretch, and thus more cells are added to these cells.

Types Of Collenchyma

The types of collenchyma are:

Angular Collenchyma

Angular collenchyma shows the thickening of the cell wall at cell angles, making the cells angular in shape. Angular collenchyma is generally localised in the stem of herbaceous plants; hence, it supports the plant and provides strength for its framework. Angular thickenings are best fitted to withstand mechanical stresses.

Tangential Collenchyma

Tangential collenchyma is characterised by the thickening of its walls, oriented in a parallel manner relative to the surface of the organ of the plant hence making it appear to be more elongated. This form occurs most conspicuously in the stems and the leaves of plants and the major function is that it supports the shape of the plant as well as the weight without hampering flexibility and growth.

Lacunar Collenchyma

Lacunar collenchyma contains intercellular spaces or lacunae between cells. They are not as thickened as angular or tangential collenchyma. This type of collenchyma originates quite frequently in regions where there is an advantage to providing space for intercellular air exchange, the most common site being in the petioles and stems of some plants.

Functions Of Collenchyma

The functions are defined below:

Mechanical Support

Collenchyma cells are photosynthetic and, essentially, they provide mechanical support to the growing plant tissues, mainly in regions that continue to elongate. So in this way, this ability to flex while maintaining strength allows plants to support their structure as they grow.

Flexibility And Growth

This unequally thickened cell wall of the collenchyma cell is responsible for their flexibility, which is important to bear plants' growth and changes in shape. At the same time, this flexibility is more vital in those parts which are young and growing.

Photosynthesis In Some Plants

Chloroplasts occur in some plant collenchyma cells and may conduct photosynthesis. This fact is especially true in leaves and stems, where the products of photosynthesis can diffuse to serve the plant directly.

Role In Healing And Repair

Collenchyma plays a role in support and repair; in particular, collenchyma can give support to a growing stem and also help a wounded stem by replacing and helping regrow from the original place of the wound. They provide a form of structural support and repair if the plant becomes damaged.

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