Editing Root (section)

== Anatomy ==
[[File:CSIRO ScienceImage 11626 Barley root.jpg|thumb|The cross-section of a [[Hordeum vulgare|barley]] root]]
Root morphology is divided into four zones: the [[root cap]], the [[apical meristem]], the elongation zone, and the hair.<ref name="Okon1993">{{cite book|author=Yaacov Okon|title=Azospirillum/Plant Associations|url=https://books.google.com/books?id=I07BKGI8rboC&pg=PA77|date=24 November 1993|publisher=CRC Press|isbn=978-0-8493-4925-6|pages=77–}}</ref> The [[root cap]] of new roots helps the root penetrate the soil. These root caps are sloughed off as the root goes deeper creating a slimy surface that provides lubrication. The apical meristem behind the root cap produces new root cells that elongate. Then, root hairs form that absorb water and mineral nutrients from the soil.<ref name=arizona>{{cite web |title=Backyard Gardener: Understanding Plant Roots |website=University of Arizona Cooperative Extension |url=https://cals.arizona.edu/yavapai/anr/hort/byg/archive/understandingplantroots.html}}</ref> The first root in seed producing plants is the [[radicle]], which expands from the plant embryo after seed germination.

When dissected, the arrangement of the cells in a root is [[root hair]], [[Epidermis (botany)|epidermis]], [[epiblem]], [[Cortex (botany)|cortex]], [[endodermis]], [[pericycle]] and, lastly, the [[vascular tissue]] in the centre of a root to transport the water absorbed by the root to other places of the plant.{{clarify|reason=need diagram |date=March 2016}}
[[File:Ranunculus Root Cross Section.png|thumb|''Ranunculus'' root cross section]]

Perhaps the most striking characteristic of roots that distinguishes them from other plant organs such as stem-branches and leaves is that roots have an ''endogenous''<ref>{{cite book | title = College Botany | volume = 1 | vauthors = Gangulee HC, Das KS, Datta CT, Sen S | publisher = New Central Book Agency | location = Kolkata }}</ref> origin, ''i.e.'', they originate and develop from an inner layer of the mother axis, such as [[pericycle]].<ref>{{cite book | title = BOTANY For Degree Students | edition = 6th | vauthors = Dutta AC, Dutta TC | publisher = Oxford University Press }}</ref> In contrast, stem-branches and leaves are ''exogenous'', ''i.e.'', they start to develop from the cortex, an outer layer.

In response to the concentration of nutrients, roots also synthesise [[cytokinin]], which acts as a signal as to how fast the shoots can grow. Roots often function in storage of food and nutrients. The roots of most vascular plant species enter into symbiosis with certain [[fungi]] to form [[mycorrhiza]]e, and a large range of other organisms including [[bacteria]] also closely associate with roots.<ref>{{Cite book|last=Sheldrake|first=Merlin|title=Entangled Life|publisher=Bodley Head|year=2020|isbn=978-1847925206|pages=148}}</ref>

[[File:Kiental entre Herrsching y Andechs, Alemania 2012-05-01, DD 12.JPG|thumb|Large, mature tree roots above the soil]]