Editing Tuber (section)

== Root tubers ==
[[File:Ipomoea batatasL ja01.jpg|thumb|upright=1.7|Freshly dug [[sweet potato]] plants with tubers]]
[[File:Hem Root.jpg|thumb|''[[Hemerocallis]]'' tuber roots]]

A root tuber, tuberous root or storage root is a modified lateral [[root]], enlarged to function as a [[storage organ]]. The enlarged area of the tuber can be produced at the end or middle of a root or involve the entire root. It is thus different in origin, but similar in function and appearance, to a stem tuber. Plants with tuberous roots include the [[sweet potato]] (''Ipomoea batatas''), [[cassava]], [[dahlia]], and ''[[Sagittaria]]'' (arrowhead) species.{{cn|date=October 2023}}

Root tubers are perennating organs, thickened roots that store nutrients over periods when the plant cannot actively grow, thus permitting survival from one year to the next. The massive enlargement of secondary roots typically represented by sweet potato have the internal and external cell and tissue structures of a normal root; they produce [[adventitious roots]] and stems, which again produce adventitious roots.<ref name=Davis1994>{{Citation| editor1-last = Davis | editor1-first = Tim D.| editor2-last = Haissig | editor2-first = Bruce E.| year = 1994| title = Biology of Adventitious Root Formation| pages = 17 | isbn = 978-0-306-44627-6| publisher = Plenum Press| location = New York}}</ref>

In root tubers, there are no nodes and internodes or reduced leaves. The proximal end of the tuber, which was attached to the old plant, has crown tissue that produces buds which grow into new stems and foliage.<ref name=Kyte1996>{{Citation | last1 = Kyte | first1 = Lydiane | last2 = Kleyn | first2 = John | year = 1996 | title = Plants from Test Tubes: An Introduction to Micropropagation | pages = 23–24 | isbn = 978-0-88192-361-2 | publisher = Timber Press | location = Portland, Or. }}</ref> The distal end of the tuber normally produces unmodified roots. In stem tubers the order is reversed, with the distal end producing stems. Tuberous roots are biennial in duration: the plant produces tubers the first year, and at the end of the growing season, the shoots often die, leaving the newly generated tubers; the next growing season, the tubers produce new shoots. As the shoots of the new plant grow, the stored reserves of the tuber are consumed in the production of new roots, stems, and reproductive organs; any remaining root tissue dies concurrently to the plant's regeneration of the next generation of tubers.{{cn|date=October 2023}}

''[[Hemerocallis fulva]]'' (orange daylily) and a number of [[daylily]] hybrids have large root tubers; ''H. fulva'' spreads by underground stolons<ref>{{eFloras|2|200027676|Hemerocallis fulva |last1=Chen |first1=Xinqi |first2=Junko |last2=Noguchi |volume=24 |access-date=27 April 2018 |url-status=live |archive-url=https://web.archive.org/web/20161114001709/http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200027676 |archive-date=14 November 2016 }}</ref> that end with a new fan that grows roots that produce thick tubers and then send out more stolons.<ref name=Mansfeld2001>{{Citation |last = Mansfeld | first =  Rudolf |year = 2001 |title = Mansfeld's Encyclopedia of Agricultural and Horticultural Crops |pages = 2231 |isbn = 978-3-540-41017-1 |publisher = Springer | location = Berlin }}</ref><ref>http://sain.utk.edu/invasives/species32.shtml{{Dead link|date=January 2019 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

Plants with root tubers can be propagated from late summer to late winter by digging up the tubers and separating them, making sure that each piece has some crown tissue for replanting.{{cn|date=October 2023}}
[[File:World Primary Crops Harvested Area By Commodity Group.svg|thumb|Roots and tubers are some of the most widely harvested crops in the world.]]
Root tubers are a rich source of nutrients for humans and wild animals, e.g. those of ''Sagittaria'' plants which are eaten by ducks.<ref name="Hammerson2004">{{Citation | last = Hammerson | first =  Geoffrey A. | year = 2004 | title = Connecticut Wildlife: Biodiversity, Natural History, and Conservation | pages = 89 | isbn = 978-1-58465-369-1 | publisher = University Press of New England | location = Hanover }}</ref>