Root-internal Structure

Primary structure of root. The root is differentiated into three regions-epidermis, cortex and vascular cylinder or stele.

A. Monocot Root
In monocot root secondary growth is absent and so there is no distinction between young and old root of a monocot plant. The internal structure resembles that of dicot root except for differences in cortex and vascular tissue. The roots has three distinct regions:

1. Epidermis. It is the outermost layer and is also called epiblema. It consists of closely packed, thin walled parenchymatous cells. Root hairs, if present, are unicellular due to which is also called piliferous layer. the epidermis is without cuticle and stomata.

2. Cortex. It consists of thin walled parenchymatous cells and rounded having intercellular spaces in them. They store food in form of starch grains. It is thicker than cortex of a dicot root. The inner most layer of cortex is made up of closely fitted barrel shaped cells, and is called endodermis. The radial and tangential walls have thickenings of lignin and suberin-called Casparian strips. The endodermal cells opposite the protoxylem are thin walled to permit free passage of water and minerals from cortex to xylem. These are called passage cells.