Editing Rhizoid

{{Short description|Protuberances that extend from the lower epidermal cells of bryophytes and algae}}
{{distinguish|Rhizome}}
{{More citations needed|date=September 2021}}
'''Rhizoids''' are protuberances that extend from the lower [[epidermis (botany)|epidermal cells]] of [[bryophyte]]s and [[algae]]. They are similar in structure and function to the [[root hair]]s of [[vascular plant|vascular]] [[land plants]]. Similar structures are formed by some [[fungi]]. Rhizoids may be unicellular or multicellular.<ref>{{cite book | last= Fletcher |first=Robert L. | date = 1987 | title = Seaweeds of the British Isles, Volume 3 Fucophyceae (Phaeophyceae) | publisher = British Museum (Natural History) | isbn = 0-565-00992-3 }}</ref>

== Evolutionary development ==
Plants originated in aquatic environments and gradually migrated to land during their long course of evolution. In water or near it, plants could absorb water from their surroundings, with no need for any special absorbing organ or tissue. Additionally, in the primitive states of plant development, tissue differentiation and division of labor were minimal, thus specialized water-absorbing tissue was not required. The development of specialized tissues to absorb water efficiently and anchor the plant body to the ground enabled the spread of plants onto land.<ref name = "Jones_2012">{{cite journal | vauthors = Jones VA, Dolan L | title = The evolution of root hairs and rhizoids | journal = Annals of Botany | volume = 110 | issue = 2 | pages = 205–212 | date = July 2012 | pmid = 22730024 | pmc = 3394659 | doi = 10.1093/aob/mcs136 }}</ref>

== Description ==
Rhizoids absorb water mainly by [[capillary action]] in which water moves up between threads of rhizoids; this is in contrast to roots in which water moves up through a single root. However, some species of bryophytes do have the ability to take up water inside their rhizoids.<ref name = "Jones_2012" />

=== Land plants ===
In land plants, rhizoids are [[trichome]]s that anchor the [[plant]] to the ground. In the [[Marchantiophyta|liverworts]], they are absent or unicellular, but they are multicellular in [[moss]]es. In [[vascular plant]]s, they are often called [[Trichome#Trichome and root hair development|root hairs]] and may be unicellular or multicellular.

=== Algae ===
In certain [[algae]], there is an extensive rhizoidal system that allows the alga to anchor itself to a sandy substrate from which it can absorb nutrients.<ref>{{cite journal| doi=10.1016/j.aquabot.2009.10.012 | volume=92 | issue=2 | title=Comparative phosphate acquisition in giant-celled rhizophytic algae (Bryopsidales, Chlorophyta): Fleshy vs. calcified forms | year=2010 | journal=Aquatic Botany | pages=157–160 | vauthors = Demes KW, Littler MM, Littler DS }}</ref> Microscopic free-floating species, however, do not have rhizoids at all.<ref>{{cite book | vauthors = Smith GM | date = 1955 | title = Cryptogamic Botany, Volume 1 Algae and Fungi | publisher = McGraw-Hill Book Company Inc }}</ref>

=== Fungi ===
In [[fungi]], rhizoids are small branching [[hyphae]] that grow downwards from the [[stolon]]s and anchor the fungus to the [[Substrate (biology)|substrate]], where they release digestive [[enzyme]]s and absorb digested organic material.{{Citation needed|date=July 2024}}

== See also ==
{{Portal|Fungi}}
* [[Rhizine]], the equivalent structure in [[Lichen#Internal structure and growth forms|lichens]]

== References ==
{{reflist}}

== Further reading ==
{{refbegin}}
* {{cite encyclopedia | vauthors = Hogan CM | date = 2010 | url = https://editors.eol.org/eoearth/wiki/Fern | title = Fern | encyclopedia = Encyclopedia of Earth | veditors = Basu S, Cleveland C | publisher = National Council for Science and the Environment | location = Washington DC }}
{{refend}}

== External links ==
* {{Cite NSRW|short=x|wstitle=Rhizoids}}
* {{Cite NIE|short=x|wstitle=Rhizoids}}

{{Botany|state=collapsed}}

[[Category:Fungal morphology and anatomy]]
[[Category:Bryophytes]]
[[Category:Plant anatomy]]

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[[he:מורפולוגיה של הצמח - מונחים#איברים בצמחים פרימיטיביים]]