Collenchyma

Collenchyma is a living, elongated cell with irregularly thick cell walls, found mainly in the cortex of stems and leaves of plants. Collenchyma tissue forms the fundamental or ground tissues in plants along with parenchyma and sclerenchyma.

Collenchyma was discovered by Scheilden in the year 1839.

They are found below the epidermis or the outer layer of cells in young stems and in leaf veins of plants, while they are usually absent in roots.

• Living, elongated cells with the presence of cytoplasm and irregular cell wall
• Varies widely in shape and size, based on which they can be round, elliptical, or elongated
• The cell wall is thick with deposition of cellulose, hemicellulose, and pectin but devoid of lignin (non-lignified). Some cells have tannins.
• Have a compact cell arrangement with little or no space between the cells
• Have a prominent nucleus and all cell organelles including vacuole
• Very rarely have chloroplast and thus participate in food production by photosynthesis

Based on their location and the type of polysaccharide-deposition around the cell wall, collenchyma cells are classified into different types with each of them performing the following functions:

• Strength and Protection: Providing rigidity to the developing plant parts due to polysaccharide deposition in their cell wall
• Support: Giving additional back up to the growing plant parts such as stems and leaves to withstand stress 
• Growth: Helping in elongation and development of plants
• Storage: Stores defensive antibacterial compounds that protect the plant against bacterial invasion
• Food Production: Chloroplast containing cells helps the plant to produce food by photosynthesis