Endodermis

The endoderm is a feature of the plant roots, but also occurs in rhizomes. It is the most obvious layer of the central cylinder of the bark. Passage cells of the endodermis push water into the central cylinder - root pressure is created. The endoderm forms a cylinder around the vascular system of the root. Anticlinal the cell walls of the cells contain a Suberinschicht endodermal, this is the Casparian strips. The endodermis is not to be confused with the endoderm (also endoderm ).

There are different stages of cell wall development: primary endodermis, endodermis secondary and tertiary endodermis. The primary endodermis (mostly in dicots ) consists of cells embedded in the horizontal and radial walls lignin and suberin are ( Casparischer stripes). The cell walls of secondary endodermis ( in gymnosperms ) are additionally suberinisiert all sides thin. Only passage cells are then to water transport in the situation. In the tertiary endodermis (typical in most monocots ) is asymmetric supported at the inner and side walls additional lignified cellulose, which leads to a marked thickening of the wall.

The purpose of the endodermis is that taken by the root harmful substances not pass through the apoplast in the central cylinder (eg heavy metals). There are in the endodermis but individual unthickened passage cells through which water can pass selectively in the central cylinder.