Endodermis

The endodermis is a feature of the roots of plants, but is also found in rhizomes . It is the layer of the bark closest to the central cylinder . Passage cells of the endodermis press water into the central cylinder - root pressure is created. The endodermis forms a cylinder around the vascular system of the root. The anticlinal cell walls of the endodermal cells contain a layer of lignin , this is the Casparian stripe . The endodermis should not be confused with the endoderm (also called the endoderm) .

There are different stages of cell wall development: primary endodermis, secondary endodermis and tertiary endodermis. The primary endodermis (mostly in dicotyledons) consists of cells in whose horizontal and radial walls lignin and suberin are embedded ( Casparian stripe ). The cell walls of the secondary endodermis (in gymnosperms) are additionally thinly suberinized on all sides. Only passage cells are then still able to transport water. In the tertiary endodermis (typical of most monocotyledons) additional, lignified cellulose is asymmetrically deposited on the inner and side walls , which leads to a significant wall thickening.

The purpose of the endodermis is that harmful substances (e.g. heavy metals) absorbed by the root do not get through the apoplast into the central cylinder. In the endodermis, however, there are individual, unthickened passage cells through which water can selectively reach the central cylinder.

literature

Andreas Bresinsky , Christian Körner , Joachim W. Kadereit , Gunther Neuhaus , Uwe Sonnewald : Textbook of botany . Founded by Eduard Strasburger . 36th edition. Spectrum Akademischer Verlag, Heidelberg 2008, ISBN 978-3-8274-1455-7 .

Individual evidence

↑ Sadaf Naseer, Yuree Lee, Catherine Lapierre, Rochus Franke, Christiane Nawrath: Casparian strip diffusion barrier in Arabidopsis is made of a lignin polymer without suberin . In: Proceedings of the National Academy of Sciences . tape 109 , no. 25 , June 19, 2012, ISSN 1091-6490 , p. 10101-10106 , doi : 10.1073 / pnas.1205726109 , PMID 22665765 , PMC 3382560 (free full text).

[1] Sadaf Naseer, Yuree Lee, Catherine Lapierre, Rochus Franke, Christiane Nawrath: Casparian strip diffusion barrier in Arabidopsis is made of a lignin polymer without suberin . In: Proceedings of the National Academy of Sciences . tape 109 , no. 25 , June 19, 2012, ISSN 1091-6490 , p. 10101-10106 , doi : 10.1073 / pnas.1205726109 , PMID 22665765 , PMC 3382560 (free full text).