Tissues Test - 11

ÂCollenchyma tissue is found in leaf stalks below the epidermis.

ÂThe cells of this tissue are living, elongated and irregularly thickened at the corners.

ÂThere is very little intercellular space.

ÂSclerenchyma is present in stems, around vascular bundles, in the veins of leaves.

ÂMeristematic cells divide frequently and give rise to new cells and hence they need dense cytoplasm and thin cell wall.

ÂThey also lack vacuoles or have small vacuoles, and no intercellular spaces.

ÂThe substance that strengthens sclerenchyma cells is lignin.

ÂLignin is cement like pigment which helps in protection and thickening of the sclerenchyma walls.

ÂLignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity and do not rot easily.

• Permanent tissues are formed due to differentiation.

• The cells of the meristematic tissues take up a specific role and lose the ability to divide.

• As a result, they form a permanent tissue.

• This process of taking up a permanent shape, size, and a function is called differentiation.

• Cells of meristematic tissue differentiate to form different types of permanent tissue.

• Parenchyma is a simple permanent tissue.

• A few layers of cells form the basic packing tissue called parenchyma.

• It consists of unspecialised cells with thin cell walls. They are live cells.

• They are usually loosely packed, so that large spaces between cells are found in this tissue.

• Parenchyma tissue provides support to plants and also stores food.

• The parenchyma of stems and roots also stores nutrients and water.

• Parenchyma tissue does not provide the plant flexibility.

• The flexibility in plants is due to another permanent tissue, collenchyma.