Question

What is the role of the Casparian Strip?

Answer 1

Hint: Casparian strips are modified primary carbohydrate cell walls in which lignin and suberin deposition in the primary cell wall and middle lamella distinguishes the radial sections of the cell walls. Suberin, lignin, and certain structural proteins are among the substances deposited in the Casparian strips.

Complete answer:
 Suberin, a waxy material that is impervious to water, is deposited in the root's endodermis. It works as an apoplastic diffusion barrier and regulates the flow of water into the circulatory system. The symplastic system transports water to the xylem cells.

The Casparian strip is a thickening in the root endodermis (radial and cell walls) of vascular plants that looks like a band (Pteridophytes and Spermatophytes). The region is primarily made up of lignin, and its width varies between species. Because the Casparian strip is impervious to water, it can regulate the flow of water and inorganic salts between the cortex and the vascular bundle, preventing water and inorganic salts from being transported to the stele via the apoplast, forcing them to enter the cell membrane and travel to the stele via the symplastic pathway, effectively blocking the cell's internal and external objects.

A combination of apoplastic, symplastic, and transcellular routes transport solutes and water radially through the roots. Hydrophobic barriers in both the endo- and exodermis hinder the apoplastic pathway, whereas the latter two pathways require solutes to cross plasma membranes at least twice. Furthermore, the thick cytoplasm in the meristematic root zone at the root tip acts as a substantial solute barrier.

Note: Harmful substances, such as herbicides, cannot flow through the Casparian strip, which acts as a barrier. Such poisons would have travelled throughout the plant via the xylem, killing it if not for this strip. It also keeps unwanted organisms out of the plant, where they might cause illnesses.