Endodermis

The innermost layer of a plant root’s cortex, regulating water and dissolved substances entering the vascular tissue through selective barriers.

Casparian strip: A band of suberin and lignin in endodermal cell walls that blocks apoplastic transport. It seals the spaces between cells, forcing water and solutes through cell membranes.
Root cortex: Ground tissue between a plant root’s epidermis and its central vascular cylinder. The endodermis forms the innermost boundary of this tissue.
Root pressure: Positive pressure that develops in root xylem when ion accumulation draws water into the vascular tissue. Selective ion entry across the endodermis contributes to the gradients that generate this pressure.
Exodermis: A specialized outer layer of some roots, located near the root surface and capable of forming protective wall barriers. Unlike the endodermis, it restricts movement at the outer edge of the cortex.
Apoplastic transport: Movement of water and solutes through cell walls and extracellular spaces without crossing cell membranes. The endodermis interrupts this route at the Casparian strip.
Root epidermis: The outermost cell layer of a plant root, which contacts soil and absorbs water and minerals. Water entering the root from the soil must pass inward beyond this layer.
Mineral nutrient uptake: The acquisition and transport of essential inorganic elements from soil into plants. Endodermal selectivity influences which absorbed minerals reach the vascular system.
Pericycle: A cell layer immediately inside the endodermis that can initiate lateral roots and secondary growth. It lies on the vascular side of the endodermis rather than forming the cortex’s inner boundary.
Symplastic transport: Movement of substances through plant-cell cytoplasm connected by plasmodesmata. It provides a cell-to-cell route across the endodermis after the apoplastic pathway is blocked.
Xylem: Plant vascular tissue that conducts water and dissolved minerals, mainly from roots toward shoots. The endodermis regulates substances before they enter the root’s xylem.

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