Cross Section Of Young Dicot Root

This is a typical cross-section of a young dicot root taken in the region of root hair proliferation (see 'Plant Root Growth'), before lateral secondary growth has begun. Hence, the lateral meristematic tissue (cambium) is not yet present.

EPIDERMIS - Developed from the protoderm, it forms a cover, one cell thick, around the root's perimeter. In the region just back from the root tip, cells produce extensions as root hairs to increase the root's water-absorbing potential.

CORTEX - Developed from the ground meristem, these are typical 'fleshy' parenchyma cells with thin walls, large vacuoles and air spaces between cells, facilitating storage of food and water.

In roots of some plants (bog-type plants), some of the cortex cells are lost, producing even more air spaces 'aerenchyma', which allow gases to diffuse WITHIN the plant to and from the root tips.

ENDODERMIS - Surrounds the vascular tissue and can be seen as the innermost layer of the cortex. Unlike the epidermis, each cell wall contains a vertical ring of fatty suberin, called the 'Casparian Strip', making the wall impervious and thus keeping out unwanted solutes.

PERICYCLE - A layer one to several cells thick, between vascular tissue and endodermis. This is modified parenchyma which retains its capacity for cell division and produces the lateral roots which then punch their way out through the outer tissues.

VASCULAR TISSUES - PHLOEM AND XYLEM form an inner stele through the centre of the root, right up to the hypocotyl, where the root joins the stem. The structure then changes into that of a typical stem.