Editing Lignotuber (section)

{{short description|Swelling of the root which protects against fire and other hazards}}
{{Use dmy dates|date=June 2023}}
[[File:Cussonia paniculata - Lignotuber.JPG|thumb|right|Lignotuber of ''[[Cussonia paniculata]]'' partly exposed above ground]]
[[File:Camphor Trees2, Vergelegen.JPG|thumb|[[Cinnamomum camphora|Camphor trees]] at the Vergelegen Estate]]
[[File:Lignotuber face Roosevelt Redwood Grove.jpg|thumb|Lignotuber at the Roosevelt Grove of Humboldt Redwoods State Park.]]
[[File:Lignotuber active redwood.jpg|thumb|Lignotuber actively budding, Prairie Creek Redwoods State Park.]]

A '''lignotuber''' is a woody swelling of the [[root crown]] possessed by some plants as a protection against destruction of the plant stem, such as by fire.<ref>{{cite journal |author1=Paula S. |author2=Naulin P.I. |author3=Arce C. |author4=Galaz C. |author5=Pausas J.G. |year=2016 |title=Lignotubers in Mediterranean basin plants |doi=10.1007/s11258-015-0538-9 |journal=Plant Ecology |volume=217 |issue=6 |pages=661–676 |bibcode=2016PlEco.217..661P |citeseerx=10.1.1.707.1505 |s2cid=17448762}}</ref> Other woody plants may develop basal [[burl]]s as a similar survival strategy, often as a response to [[coppicing]] or other environmental stressors. However, lignotubers are specifically part of the normal course of development of the plants that possess them, and often develop early on in growth.<ref name=":0">{{Cite book |last1=Keeley |first1=Jon E. |url=https://books.google.com/books?id=Qx2adrY9AukC&q=umbellularia |title=Fire in Mediterranean Ecosystems |last2=Bond |first2=William J. |last3=Bradstock |first3=Ross A. |last4=Pausas |first4=Juli G. |last5=Rundel |first5=Philip W. |date=2012 |publisher=Cambridge University Press |isbn=978-0-521-82491-0 |language=en}}</ref> The crown contains [[bud]]s from which new stems may sprout, as well as stores of [[starch]] that can support a period of growth in the absence of [[photosynthesis]]. The term "lignotuber" was coined in 1924 by Australian [[botanist]] Leslie R. Kerr.{{cn|date=May 2021}}

Plants possessing lignotubers include many species in Australia: ''[[Eucalyptus marginata]]'' (jarrah), ''[[Eucalyptus brevifolia]]'' (snappy gum) and ''[[Eucalyptus ficifolia]]'' (scarlet gum) all of which can have lignotubers {{convert|10|ft|m|0|spell=in}} wide and {{convert|3|ft|m|0|spell=in}} deep, as well as most [[mallee (habit)|mallee]]s (where it is also known as a '''mallee root'''<ref name=ga2006>{{cite web |title=Mallee Trees |first=Sophie |last=Thomson |website=[[Gardening Australia]] |publisher=[[Australian Broadcasting Corporation]] |date=14 October 2006 |url=https://www.abc.net.au/gardening/factsheets/mallee-trees/9427326 |access-date=25 May 2021 |others=Series 17, Episode 35 |archive-date=11 November 2020 |archive-url=https://web.archive.org/web/20201111200202/https://www.abc.net.au/gardening/factsheets/mallee-trees/9427326 |url-status=live }}</ref>) and many ''[[Banksia]]'' species.

Plants possessing lignotubers on the western coast of the USA include [[Aesculus californica|California buckeye]], [[Sequoia sempervirens|coast redwood]], [[Umbellularia|California bay laurel (aka Oregon myrtle)]], and multiple species of [[manzanita]] and ''[[Ceanothus]]''.<ref name=":0" />

At least 14 species in the [[Mediterranean region]] have been identified as having lignotubers (as of 1993). Lignotubers develop from the [[cotyledon]]ary bud in seedlings of several [[Quercus|oak]] species including cork oak ''[[Quercus suber]]'', but do not develop in several other oak species, and are not apparent in mature cork oak trees.<ref name=corkoak>{{cite journal |title=Lignotuber Ontogeny in the Cork-Oak (''Quercus suber''; Fagaceae). I. Late Embryo |author1=M. L. Molinas |author2=D. Verdaguer |journal=American Journal of Botany |volume=80 |issue=2 |year=1993 |pages=172–181 |doi=10.2307/2445037 |jstor=2445037}}</ref>

The fire-resistant lignotubers of ''[[Erica arborea]]'', known as "briar root", are commonly used to make smoking pipes.

The largest known lignotubers (also called "root collar burls") are those of the Coast Redwood ''([[Sequoia sempervirens]])'' of central and northern California and extreme southwestern [[Oregon]]. A lignotuber washed into [[Big Lagoon (California)|Big Lagoon]], California, by the full gale storm of 1977 was {{cvt|41|ft|m}} in diameter and about half as tall and estimated to weigh {{cvt|525|ST}}.<ref>{{cite journal |last=Del Tredici |first=Peter |date=Fall 1999 |title=Redwood Burls – Immortality Underground |journal=Arnoldia |volume=59 |issue=3 |page=photo and caption p. 19}}</ref>  The largest [[Dicotyledon|dicot]] lignotubers are those of the Chinese Camphor Tree, or Kusu ''([[Cinnamomum camphora]])'' of Japan, China and the Koreas. Ones at the [[Vergelegen|Vergelegen Estate]] in [[Cape Town]], South Africa, which were planted in the late 1600s have muffin-shaped lignotubers up to {{convert|6|ft|m|0|spell=in}} high and about {{cvt|30|ft|m|0}} in diameter.<ref>{{cite book |last=Esterhuyse |first=Neels |display-authors=etal |title=Remarkable Trees of South Africa |location=Pretoria |publisher=Briza Publications |pages=102–103}}</ref><ref>{{cite book |last=Pakenham |first=Thomas |title=Remarkable Trees of the World |location=New York |publisher=W. W. Norton and Co. |pages=122–123}}</ref> Perhaps the largest lignotuber in Australia would be that of "Old Bottle Butt", a Red Bloodwood Tree (''[[Corymbia gummifera]]'') near [[Wauchope, New South Wales]], that has a lignotuber about {{cvt|8|ft}} in height and {{cvt|16.3|m}} in circumference at breast height.<ref>{{cite web |url=http://www.nationalregisterofbigtrees.com.au/listing_view.php?listing_id=535 |title=National Register Of Big Trees |access-date=27 October 2017 |archive-date=29 October 2017 |archive-url=https://web.archive.org/web/20171029012437/http://www.nationalregisterofbigtrees.com.au/listing_view.php?listing_id=535 |url-status=live }}</ref> A lignotuber should not be confused with a [[xylopodium]]. Lignotubers are compact, even round. A xylopodium is diffuse and are sometimes called "underground trees".<ref>{{cite book | editor= Paulo S. Oliveira | date= 2002 | title= The Cerrados of Brazil | location= New York | publisher= Columbia Univ. Press | pages= 96, 128-129, 132 | ISBN= 0-231-12042-7 }}</ref>

Many plants with lignotubers grow in a shrubby habit, but with multiple stems arising from the lignotuber. The term '''lignotuberous shrub''' is used to describe this habit.{{cn|date=May 2021}}