endodermis

Literally meaning "inner skin," endodermis is the layer of tissue deep in vascular plants.

It is the inner most layers of the cortex,with no intercellular spaces.There are thickenings of special materials around cell which check diffusion of water from xylem to cortex.

In plants, it is a thin layer of parenchyma found in roots, just outside the vascular cylinder(the Stele). It helps regulate the passive movements of water and ions, and consists of a single-celled ring which forms a selective barrier between the outer cortex and the inner pericycle tissue. In the roots, the endodermis cells are impregnated with suberin, (or sometimes lignin); a waxy substance which is water resistant, to form distinctive Casparian strips and prevent movement of water via the apoplast pathway. Water carrying mineral salts can only enter the root through the interior of cells (the symplast) as opposed to passing between cells (the apoplast). This means that the plant can directly regulate what enters the root proper. The endodermis cells contain starch granules as energy store. Mineral ions are actively secreted into the xylem vessels to maintain root pressure.

Epidermal cells do not have a secondary cell well. They are also primary in origin. Epidermal cells are also living upon functional maturity(unlike Sclerenchyma cells, which are dead when functionally mature).

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