Tag: simple permanent tissues

Sclerenchyma cells are characterized by relatively thick, lignified secondary cell walls. The lignified wall gives sclerenchyma cells their rigidity, and they function primarily in mechanical support and water conduction. They also make up most rigid parts of the plant (e.g., seed coats and some fruit walls) and are often positioned so that they provide mechanical protection for softer plant parts. 

Sclerenchyma is the supporting tissue in plants. Two types of sclerenchyma cells exist: fibers and sclereids. Their cell walls consist of cellulose, hemicellulose and lignin. Sclerenchyma cells are the principal supporting cells in plant tissues that have ceased elongation where as Stomata are cell structures in the epidermis of tree leaves and needles that are involved in the exchange of carbon dioxide and water between plants and the atmosphere.

Plasmodesmata are narrow channels that act as intercellular cytoplasmic bridges to facilitate communication and transport of materials between plant cells and are not found in Sclerenchyma cells. Sclerenchyma fibres are long and narrow and have thick lignified cell walls. They provide mechanical strength to the plant and allow for the conduction of water. Sclereids are specialised sclerenchyma cells with thickened, highly lignified walls with pits running through the walls.

Sclerenchyma cells have thickened lignified walls, which make them strong and waterproof. The wall of the trachea is considerably thickened and lignified.  The characteristic thickening pattern, the thickness and the lignin content of the cell wall provide the vessel rigidity and make it resistant against the collapsing effect of the intense transpiration of the leaves.

The spherical, oval or cylindrical cells with very narrow lumen; in sclerenchyma are called sclereids. Sclereids are usually found in the fruit walls of nuts, pulp of fruits like guava, pear and sapota; seed coats of legumes and leaves of tea. The gritty texture of pear or guava is because of sclereids.

Sclerenchyma tissue is composed of sclerenchyma cells, which are usually dead at maturity (i.e., have lost their protoplasts). They characteristically contain very thick, hard secondary walls lined with lignin; consequently, sclerenchyma provides additional support and strength to the plant body.