Question

What are cortex, pericycle,pith and medullary rays?

Answer 1

Dear Student

Cortex is the outer layer of the stem or root of a plant, bounded on the outside by the epidermis. It is composed mostly of undifferentiated cells usually large thin-walled parenchyma cells of the ground tissue system.

Pericycle is a cylindrical shaped region of primary tissue of root or stem that consists of parenchyma or sclerenchyma cells. It lies just inside the endodermis and forms outermost part of the stele of plants.

Pith is composed of spongy parenchyma cells and their function is to transport nutrients throughout the plants. It is found in the stem of the vascular plants.

Two system of parenchyma exist in secondary xylem, derived from meristematic cells called as ray initials and fusiform initials. The ray parenchyma is the more extensive. It forms radial sheets of tissue called medullary rays which maintain a living link through the wood between pith and cortex. Its functions include food storage, deposition of tannins, crystals and so on, radial transport of food and water, and gaseous exchange through the intercellular spaces.

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