Tag: permanent tissues and their types

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.

Sclerenchyma is the simple permanent tissue present in plants that performs the function of protection and support. Two types of sclerenchyma cells exist, fibers and sclereids. Fibres are long, narrow-lumen, thick-walled and dead cells that provide support to the internal structure of plants. Sclereids are polygonal cells that are found in fruit pulp. Parenchyma has think walled, polygonal and live cells while collenchyma has angular thickened polygonal cells.

The exocarp is the thin outermost layer (or skin) of the fruit. The mesocarp is a thick husk composed of coarse brown fibers (coir). The endocarp is the hard, but relatively thin woody inner layer of a fruit that contains the endosperm. The endosperm is partly liquid (“coconut water”) and partly solid (fibrous white coconut “flesh” or “meat”, which adheres to the inner wall of the endocarp).

There are four types of tissues present in the plants, namely vascular tissue, epidermal tissue, ground tissue and meristematic tissue. Ground tissue consists of parenchyma tissue, collenchyma tissue and sclerenchyma tissue. Parenchyma cells have thin primary walls and remain alive after they become mature. Collenchyma cells have thin primary walls with secondary thickening in some areas. They provide mechanical and structural support.

Sclereids are a reduced form of sclerenchyma cells with highly thickened, lignified cellular walls that form small bundles of durable layers of tissue in most plants. The presence of numerous sclereids form the cores of apples and produce the gritty texture of guavas and pears.

Sclerenchyma, in plants, support tissue composed of any of various kinds of hard woody cells. Mature sclerenchyma cells are usually dead cells that have heavily thickened secondary walls containing lignin.