Collenchyma: Structure, Classification and Functions

Collenchyma is a simple permanent tissue in plants. They are living cells with prominent nucleus and all the cell organelles. Each collenchymatous cell is with a large and prominent vacuole in the centre. The vacuole is filled with many secondary metabolites. Unlike parenchyma, the collenchyma cells possess thick primary cell wall. The present article discusses the Structure and Types of Collenchyma in Plants with suitable examples.

Characteristics of Collenchyma

Ø  Collenchyma cells are living cells with thick cell walls.

Ø  The cell wall of collenchyma are are NOT lignified.

Ø  The thick wall is due to the deposition of hemicellulose and pectin along with cellulose.

Ø  Wall thickening in collenchyma is greatly affected by the extent of mechanical stress.

Ø  A plant part which in severe stress or motion due to high wind are more likely to possess more thickened collenchyma.

Ø  Usually, the collenchyma occurs in the peripheral region of the plant.

Ø  In dicots, it usually occurs as hypodermis (below the epidermis).

Ø  Plant parts with ridges and furrows, the collenchyma cells occupies at the ridges.

Ø  Collenchyma also occurs in the dicot leaves above the petiole, midrib and leaf veins.

Ø  Very rarely, the collenchyma cells may have chloroplasts.

Ø  They sometimes contain tannin deposition in the cells.

Ø  Usually, collenchymatous cells are compactly packed without any intercellular spaces.

Ø  Sometimes collenchyma cells do possess intercellular spaces.

Ø  Thickening pattern of the cell wall usually uneven and irregular.

Ø  Collenchyma is usually absent in the roots.

Ø  Collenchyma almost completely absent in monocots.

Types Collenchyma

Ø  Collenchyma is classified on the basis of nature of wall thickening and arrangement of cells.

Ø  Four different types of collenchyma are described in plants.

(1).  Angular collenchyma

(2).  Annular collenchyma

(3).  Lamellar collenchyma

(4).  Lacunar collenchyma

(1). Angular collenchyma

Ø  Cells are angled and polygonal in appearance in the cross section.

Ø  Thickening materials deposited only at the corners of the cells.

Ø  Cells are compactly packed without any intercellular spaces.

Ø  Angular collenchyma is the common type of collenchyma in plants.

Ø  Usually found below the epidermis as hypodermis.

(2). Annular collenchyma

Ø  They are uniformly thickened collenchymatous cells.

Ø  Cells appear as circular in cross section.

(3). Lamellar collenchyma

Ø  Wall thickening is restricted to tangential walls of the cells.

Ø  Due to this, the cells appeared to be arranged as tangential rows or layers.

Ø  Cells compactly packed without any intercellular spaces.

Ø  Lamellar collenchyma usually occurs in the petiole of leaves.

(4). Lacunar collenchyma

o   They are collenchymatous tissue with intercellular spaces.

o   Wall thickening is restricted around the intercellular spaces.

o   Cells appear as spherical or oval in cross section.

o   Lacunar collenchyma usually occurs in the fruit walls.

Functions of Collenchyma in Plants

Ø  Collenchyma is the living mechanical tissue in the plants.

Ø  They provide mechanical support mainly in the primary plant parts such as young stem, roots and leaves.

Ø  They are more flexible than sclerenchyma

Ø  Hence can bend the plant parts without breaking the structures.

Ø  Collenchyma permits the growth and elongation of plant parts.

Ø  Collenchyma with chloroplasts can perform photosynthesis

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