根的基本术语

Endodermis：The innermost layer of the cortex that forms a sheath around the vascular tissue of roots and some stems.

内皮层：皮层的最内层，在根、茎的导管组织周围形成一道叶鞘（茎衣）。

Exodermis：【植】外皮层, 下皮；各种兰类的木栓质表皮的下层细胞。

Suberin：A waxy waterproof substance present in the cell walls of cork tissue in plants.

软木脂：植物木栓层中细胞之间细胞壁中的一种蜡状水密物质。

Casparian strip：[植]凯氏带。In plant anatomy, the Casparian strip is a band of cell wall material deposited on the radial and transverse walls of the endodermis, which is chemically different from the rest of the cell wall. It is used to block the passive flow of materials, such as water and solutes into the stele of a plant. The band was first recognized as a wall structure by Robert Caspary (1818–1887).

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https://www.360docs.net/doc/6b1070665.html,/2010/07/expert-eye-carbohydrates-and-amino-acid-products/ Endodermis and Exodermis in Roots

https://www.360docs.net/doc/6b1070665.html,/WileyCDA/ElsArticle/refId-a0002086.html

Roots of terrestrial plants are designed to take up water and nutrients. At the same time, uptake of unwanted compounds, for example toxic, and infection by soil borne pathogens must be avoided. Specific unicellular tissues, the endodermis and the exodermis, allow roots to establish and maintain this selectivity. The endodermis represents an unicellular cell layer separating the central cylinder of the root from the cortex. The exodermis represents an unicellular cell layer located at the outer surface of the root directly below the root epidermis. Both tissues are characterised by specific cell wall modifications. In early developmental stages the anticlinal radial walls exhibit Casparian bands, composed of the polymers suberin and lignin. In a subsequent developmental state a suberin lamella is deposited on the inner surface of endo- and exodermal cell walls. These apoplastic barriers, mainly composed of suberin, significantly affect radial uptake of water and dissolved nutrients and radial loss of oxygen.

Key Concepts:

?Casparian bands, composed of lignin and suberin, form characteristic cell wall modifications in radial walls of endodermal and exodermal cells.

?Suberin lamellae are deposited onto the inner surface of endodermal and exodermal cell walls.

?Apoplastic barriers in roots are established by the deposition of suberin into and onto the cell wall.

?Suberised apoplastic barriers in roots help to establish root selectivity in nutrient uptake.

?The endodermis, forming an ‘inner’ apoplastic barrier in the root, is important in preventing nutrients actively concentrated in the xylem from passively diffusing back to the soil.

?The exo dermis, forming an ‘outer’ apoplastic barrier at the root surface, mainly establishes the root/soil interface between the root and the soil environment surrounding the root.

?As an adaptation to various environmental stress factors (e.g. drought, salt, heavy metal stress, oxygen deficiency, etc.) suberisation of apoplastic barriers is significantly modified.

Fatty acid elongases and cytochrome P450 hydroxylases represent important key enzymes in suberin biosynthesis.

Keywords: apoplastic barrier; Casparian band; endodermis; exodermis; hypodermis; nutrient uptake; plant root; suberin; transport