(botany) A strip or a band of cell wall material around the walls of endodermal cells of roots
The Casparian strip is a strip or a band of cell wall material in the roots of plants. It is particularly found as a thickening on the radial and transverse walls of the endodermal cells of the root. The major component of the Casparian strip is suberin. Suberin is a lipophilic biopolymer that acts as a protective barrier against excessive water loss. In roots, the presence of suberin in the Casparian strip makes it distinct from the rest of the cell wall (which mostly has lignin). Because of the suberin in the Casparian strip, the passive flow of materials, e.g. water and solutes, into the stele is prevented. Water and nutrients absorbed by the roots are blocked from entering the stele via the apoplastic route. As a result, solutes flow via the symplastic route. This is important so that there would be selective passage of solutes, especially when they might bring harm to the plant.
The Casparian strip is named after the person who first recognized it, Robert Caspary (1818-1887).1
1 CTI Reviews. (2017). Raven Biology of Plants: Biology, Botany. Cram101 Textbook Reviews.