Collenchyma is a type of permanent tissue found in plants. Permanent tissues lose the ability to divide further. They attain a definite shape, size and function.
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Permanent tissues are of two types: Simple and Complex. Collenchyma, parenchyma and sclerenchyma are the three types of simple permanent tissues. Simple tissues are made up of only one type of cell and all the cells perform the same function.
It is a supportive tissue made up of living cells. It is flexible tissue and provides support to soft and non-woody plant organs. The main characteristics of collenchyma cells are:
- The cells are mostly elongated, spherical, oval or polygonal in shape.
- Cells are alive at maturity.
- They contain a primary cell wall.
- The primary cell wall is unevenly thickened and mostly thickened at the corners.
- Cellulose, hemicellulose and pectin deposition in the cell wall makes it thick.
- They are compactly arranged and intercellular spaces are mostly absent.
- They often contain chloroplasts and store food.
- They are found under the epidermis of most dicot plants. E.g. in the young stem, midrib and petiole of leaves, etc.
- They can extend and adjust to the growth of the organs like stem and leaves.
- At the time of the secondary growth, collenchymatous tissues get crushed with the development of secondary tissues.
- They provide mechanical support to the growing parts of the plant, e.g. petiole, young stem, etc.
Types of Collenchyma
Collenchyma is classified into four types based on the cell wall thickening. They are:
1. Angular Collenchyma
It is the most common type of collenchyma. In this type of collenchyma cells, thickening of walls occurs only at the corners. Intercellular spaces are absent and they have a circular lumen. E.g. Cucurbita
2. Lacunar Collenchyma
This type of collenchyma has intercellular spaces. In this type of collenchymatous cells, thickening is more at the places adjacent to intercellular spaces. E.g. stems of Malva, petioles of Salvia, etc.
3. Lamellar Collenchyma
They are also called plate collenchyma. They have thickened tangential walls and are arranged into ordered rows. E.g. stem of Clerodendron.
4. Annular Collenchyma
The cell walls are uniformly thickened.
The main function of Collenchyma is to provide mechanical support to the growing young parts of the plants.
- It provides flexibility and support to the growing parts.
- It grows with the growing part of the plant.
- It protects leaf margins from tearing.
- It undergoes dedifferentiation to form phellogen or cork cambium and regain meristematic activity.
- It often contains chloroplasts and performs photosynthesis and accumulates food.
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