Rhizodermis is the
root
In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the sur ...
epidermis
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the ...
(also referred to as epiblem), the outermost primary
cell layer of the root.
Specialized rhisodermal cells,
trichoblasts, form long tubular structures (from 5 to 17 micrometers in diameter and from 80 micrometers to 1.5 millimeters in length) almost perpendicular to the main cell axis -
root hair
Root hair, or absorbent hairs, are outgrowths of epidermal cells, specialized cells at the tip of a plant root. They are lateral extensions of a single cell and are only rarely branched. They are found in the region of maturation, of the root. Root ...
s that absorb water and nutrients. Root hairs of the rhizodermis are always in close contact with soil particles and because of their high surface to volume ratio form an absorbing surface which is much larger than the transpiring surfaces of the plant.
With some species of the family
Fabaceae, the rhizodermis participates in the recognition and the uptake of nitrogen-fixing
Rhizobia bacteria - the first stage of nodulation leading to formation of
root nodule
Root nodules are found on the roots of plants, primarily legumes, that form a symbiosis with nitrogen-fixing bacteria. Under nitrogen-limiting conditions, capable plants form a symbiotic relationship with a host-specific strain of bacteria know ...
s. Rhizodermis plays an important role in nutrient uptake by the plant roots.
In contrast with the epidermis, rhizodermis contains no stomata, and is not covered by cuticle. Its unique feature is the presence of root hairs. Root hair is the outgrowth of a single rhizodermal cell. They occur in high frequency in the adsorptive zone of the root. Root hair derives from a trichoblast as a result of an unequal division. It contains a large vacuole; its cytoplasm and nucleus are superseded to the apical region of the outgrowth. Although it does not divide, its DNA replicates so the nucleus is polyploid. Root hairs live only for few days, and die off in 1–2 days due to mechanical damages.
References
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Plant morphology
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