What is the endodermis of the root and what is its function?

The endodermis is a specialized single layer of cells that forms the innermost boundary of the cortex in roots, surrounding the vascular cylinder (stele). These barrel-shaped cells are characterized by the presence of Casparian strips—bands of suberin and lignin deposited in the radial and transverse walls. The endodermis functions as a selective barrier, controlling the movement of water and dissolved minerals from the cortex into the vascular tissue. The Casparian strips force all substances to pass through the cell membranes (symplastic pathway) rather than between cells (apoplastic pathway), allowing the plant to regulate nutrient uptake and prevent harmful substances from entering the vascular system. In some roots, endodermal cells may also develop additional suberin layers, further enhancing their barrier function.