Editing Ginkgo biloba (section)

==Description==
[[File:Ginkgo biloba JPG1a.jpg|thumb|''G. biloba'' in [[Tournai]], [[Belgium]]]]

Ginkgos are large trees, normally reaching a height of {{convert|20|–|35|m|ft|0|abbr=on}},<ref>{{cite book |last1=Ansari |first1=Abid A. |url=https://books.google.com/books?id=1N76DQAAQBAJ&pg=PA236 |title=Plant Biodiversity: Monitoring, Assessment and Conservation |last2=Gill |first2=Sarvajeet Singh |last3=Abbas |first3=Zahid Khorshid |last4=Naeem |first4=M. |date=2016-12-23 |publisher=CABI |isbn=978-1-78064-694-7 |language=en}}</ref> with some specimens in China being over {{convert|50|m|ft|round=5|abbr=on}}. The tree has an angular [[crown (botany)|crown]] and long, somewhat erratic branches, and is usually deep-rooted and resistant to wind and snow damage. Young trees are often tall and slender, and sparsely branched; the crown becomes broader as the tree ages. A combination of resistance to disease, insect-resistant wood, and the ability to form [[aerial root]]s and sprouts makes ginkgos durable, with some specimens claimed to be more than 2,500&nbsp;years old.<ref>{{cite web |title=Ginkgo – Ginkgo biloba – The University of Alabama Arboretum {{!}} The University of Alabama |url=https://arboretum.ua.edu/whats-growing-on/ginkgo-ginkgo-biloba/ |access-date=2022-02-26 |website=arboretum.ua.edu}}</ref>

===Leaves===
[[File:Ginkgo Biloba Leaves - Black Background.jpg|thumb|upright|Leaves in summer]]
[[File:GinkgoLeaves.jpg|thumb|upright|Leaves in autumn]]

The [[leaves]] are unique among seed plants, being fan-shaped with veins radiating out into the leaf blade, sometimes bifurcating (splitting), but never [[anastomosing]] to form a network.<ref name="More on Morphology">{{cite web |url=https://ucmp.berkeley.edu/seedplants/ginkgoales/ginkgomm.html |title=More on Morphology of the Ginkgoales |website=www.ucmp.berkeley.edu |access-date=12 August 2006 |archive-url=https://web.archive.org/web/20001017225748/http://www.ucmp.berkeley.edu/seedplants/ginkgoales/ginkgomm.html |archive-date=17 October 2000 }}</ref> Two veins enter the leaf blade at the base and fork repeatedly in two; this is known as [[dichotomous venation]]. The leaves are usually {{convert|5|–|10|cm|in|frac=2|abbr=on}}, but sometimes up to {{convert|15|cm|in|frac=2|abbr=on}} long. The old common name, ''maidenhair tree'', derives from the leaves resembling [[pinnation|pinnae]] of the maidenhair fern, ''[[Adiantum capillus-veneris]]''. Ginkgos are prized for their autumn foliage, which is a deep [[saffron yellow]].<ref>{{Cite book |last=Meyer |first=Jeffrey G. |url=https://books.google.com/books?id=nERh9pS5r5MC&pg=PA113 |title=The Tree Book: A Practical Guide to Selecting and Maintaining the Best Trees for Your Yard and Garden |date=2004 |publisher=Simon and Schuster |isbn=978-0-7432-4974-4 |page=113 |language=en}}</ref>

Leaves of long shoots are usually notched or lobed, but only from the outer surface, between the veins. They are borne both on the more rapidly growing branch tips, where they are alternate and spaced out, and also on the short, stubby spur shoots, where they are clustered at the tips. Leaves are green both on the top and bottom<ref>{{cite web |url=http://www.bio.brandeis.edu/fieldbio/emmae24/Ginkgoaceae/ginkgo.html |archive-url=https://web.archive.org/web/20040823040332/http://www.bio.brandeis.edu/fieldbio/emmae24/Ginkgoaceae/ginkgo.html |url-status=dead |archive-date=23 August 2004 |title=Ginkgo Tree |website=www.bio.brandeis.edu |access-date=18 July 2016 }}</ref> and have stomata on both sides.<ref>{{cite web |url=https://prezi.com/clwhmur-nprv/ginkgo-tree/ |title=Ginkgo Tree |website=prezi.com |access-date=18 July 2016}}</ref> During autumn, the leaves turn a bright yellow and then fall, sometimes within a short space of time (one to fifteen&nbsp;days).<ref>{{cite web |title=PlantsMap |url=https://www.plantsmap.com/organizations/25638/plants/110024 |access-date=2022-06-24 |website=Plants Map |language=en}}</ref> Leaves of the variety or forma ''G. b. tubifolia'' have funnel-shaped leaves.<ref>{{cite web | url= https://www.xs4all.nl/~kwanten/culttubifolia.htm | last= Kwant | first= Cor | title= The Ginkgo Pages | date= n.d. | access-date=October 22, 2002 }}</ref>

===Branches===
Ginkgo branches grow in length by growth of shoots with regularly spaced leaves, as seen on most trees. From the [[axil]]s of these leaves, "spur shoots" (also known as short shoots) develop on second-year growth. Short shoots have short [[internode (botany)|internode]]s (they may grow only one to two centimeters in several years) and their leaves are usually unlobed. They are short and knobby, and are arranged regularly on the branches except on first-year growth. Because of the short internodes, leaves appear to be clustered at the tips of short shoots, and reproductive structures are formed only on them (seeds and leaves are visible on short shoots). In ginkgos, as in other plants that possess them, short shoots allow the formation of new leaves in the older parts of the crown. After a number of years, a short shoot may change into a long (ordinary) shoot, or vice versa.<ref>{{Cite journal |last1=Brenner |first1=Eric D. |last2=Katari |first2=Manpreet S. |last3=Stevenson |first3=Dennis W. |last4=Rudd |first4=Stephen A. |last5=Douglas |first5=Andrew W. |last6=Moss |first6=Walter N. |last7=Twigg |first7=Richard W. |last8=Runko |first8=Suzan J. |last9=Stellari |first9=Giulia M. |last10=McCombie |first10=W. R. |last11=Coruzzi |first11=Gloria M. |date=2005-10-15 |title=EST analysis in Ginkgo biloba: an assessment of conserved developmental regulators and gymnosperm specific genes |journal=BMC Genomics |volume=6 |pages=143 |doi=10.1186/1471-2164-6-143 |doi-access=free |issn=1471-2164 |pmc=1285361 |pmid=16225698}}</ref>

[[File:Ginkgo biloba MHNT.BOT.2010.13.1.jpg|thumb|''G. biloba'' trunk cross-section]]

Ginkgo prefers full sun and grows best in environments that are well-watered and well-drained. The species shows a preference for disturbed sites; in the "semiwild" stands at [[Tianmu Mountain]]s, many specimens are found along stream banks, rocky slopes, and cliff edges. Accordingly, ginkgo retains a prodigious capacity for vegetative growth. It is capable of sprouting from embedded buds near the base of the trunk ([[lignotuber]]s, or basal chichi) in response to disturbances, such as soil erosion. Old specimens are also capable of producing aerial roots on the undersides of large branches in response to disturbances such as crown damage; these roots can lead to successful clonal reproduction upon contacting the soil. These strategies are evidently important in the persistence of ginkgo; in a survey of the "semiwild" stands remaining in [[Tianmu Mountain|Tianmushan]], 40% of the specimens surveyed were multi-stemmed, and few saplings were present.<ref name=royer>{{cite journal |first1=Dana L. |last1=Royer |first2=Leo J. |last2=Hickey |first3=Scott L. |last3=Wing |year=2003 |title=Ecological conservatism in the 'living fossil' ''Ginkgo'' |journal=Paleobiology |volume=29 |issue=1 |pages=84–104 |doi=10.1666/0094-8373(2003)029<0084:ECITLF>2.0.CO;2 |s2cid=19865243 |issn=0094-8373}}</ref>{{rp|86–87}}

=== Reproduction ===
''Ginkgo biloba'' is [[dioecy#In botany|dioecious]], with separate [[sexes]], some trees being [[female]] and others being [[male]].<ref>{{cite book |last1=Pendarvis |first1=Murray P. |url=https://books.google.com/books?id=UcRKDwAAQBAJ&pg=PA362 |title=Exploring Biology in the Laboratory, 3e |last2=Crawley |first2=John L. |date=2018-02-01 |publisher=Morton Publishing Company |isbn=978-1-61731-756-9 |language=en}}</ref> Male plants produce small [[conifer cone|pollen cones]] with [[sporophyll]]s, each bearing two [[microsporangium|microsporangia]] spirally arranged around a central axis. Sex conversion, wherein certain branches of a tree change sexes, has been observed.{{r|nagata2016}} This phenomenon is difficult to research because of its rarity as well as the practice of grafting female branches onto otherwise male trees that was common in 19th century Europe.{{r|osgf2017}}

Female plants do not produce cones. Two [[ovule]]s are formed at the end of a stalk, and after [[anemophily|wind pollination]],<ref>{{cite journal |last1=Jin |first1=Biao |last2=Jiang |first2=Xiaoxue |last3=Wang |first3=Di |last4=Zhang |first4=Lei |last5=Wan |first5=Yinglang |last6=Wang |first6=Li |date=September 2012 |title=The behavior of pollination drop secretion in Ginkgo biloba L. |journal=Plant Signaling & Behavior |language=en |volume=7 |issue=9 |pages=1168–1176 |doi=10.4161/psb.21122 |issn=1559-2324 |pmc=3489653 |pmid=22899081|bibcode=2012PlSiB...7.1168J }}</ref> one or both develop into [[fruit]]-like structures containing seeds. The fruits are 1.5–2&nbsp;cm long, with a soft, fleshy, yellow-brown outer layer (the [[sarcotesta]]) that is attractive in appearance, but contains [[butyric acid]]<ref>{{cite book |last=Raven |first=Peter H. |author2=Ray F. Evert |author3=Susan E. Eichhorn |year=2005 |title=Biology of Plants |edition=7th |location=New York |publisher=W. H. Freeman and Company |isbn=978-0-7167-1007-3 |pages=429–430}}</ref> (also known as butanoic acid) and smells foul like [[rancidification|rancid]] [[butter]] or [[vomit]]<ref>{{cite book |last=Plotnik |first=Arthur |year=2000 |title=The Urban Tree Book: An Uncommon Field Guide for City and Town |edition=1st |location=New York |publisher=Three Rivers Press |isbn=978-0-8129-3103-7 |page=[https://archive.org/details/urbantreebook00arth/page/202 202] |url=https://archive.org/details/urbantreebook00arth/page/202}}</ref> when fallen. Beneath the sarcotesta is the hard [[sclerotesta]] (the "shell" of the seed) and a papery [[endotesta]], with the [[nucellus]] surrounding the female [[gametophyte]] at the center.<ref name="Lab IX">{{cite web |url=https://ucmp.berkeley.edu/IB181/VPL/CorCon/CorCon2.html |title=Lab IX – Ginkgo, Cordaites, Conifers (2) |website=ucmp.berkeley.edu}}</ref>

{{multiple image
|align = none
|image1 = Ginkgo biloba male flower.jpg
|caption1 = Pollen cones
|image2 = Ginkgo biloba female flower.jpg
|caption2 = Ovules
}}

The fertilization of ginkgo seeds occurs via [[motility|motile]] sperm, as in cycads, ferns, mosses, and algae. The sperm are large (about 70–90&nbsp;micrometres)<ref name=Press>{{cite book |author=Vanbeek, A. |title=Ginkgo Biloba (Medicinal and Aromatic Plants: Industrial Profiles) |publisher=CRC Press |year=2000 |isbn=978-90-5702-488-7 |page=37}}</ref> and are similar to the sperm of cycads, which are slightly larger. ''Ginkgo'' sperm were first discovered by the Japanese botanist [[Sakugoro Hirase]] in 1896.<ref>{{cite journal |author=Ogura, Y. |url=http://www.biologie.uni-hamburg.de/b-online/fo47/ginkgo/ogura.htm |title=History of Discovery of Spermatozoids In ''Ginkgo biloba'' and ''Cycas revoluta'' |journal=Phytomorphology |volume=17 |pages=109–114 |date=1967 |archive-url=https://web.archive.org/web/20150926052738/http://www1.biologie.uni-hamburg.de/b-online/fo47/ginkgo/ogura.htm |archive-date=26 September 2015}}</ref> The sperm have a complex multi-layered structure, which is a continuous belt of basal bodies that form the base of several thousand flagella which have a cilia-like motion. The flagella/cilia apparatus pulls the body of the sperm forwards. The sperm have only a tiny distance to travel to the archegonia, of which there are usually two or three. Two sperm are produced, one of which successfully fertilizes the ovule. Fertilization of ginkgo seeds occurs just before or after they fall in early autumn.<ref name="More on Morphology"/><ref name="Lab IX"/> Embryos may develop in the seeds before or after they drop from the tree.<ref>{{cite journal |last1=Holt |first1=B. F. |last2=Rothwell |first2=G. W. |title=Is Ginkgo biloba (Ginkgoaceae) Really an Oviparous Plant? |journal=American Journal of Botany |volume=84 |issue=6 |pages=870–872 |year=1997 |doi=10.2307/2445823 |pmid=21708639 |jstor=2445823 |doi-access=free}}</ref>

=== Genome ===
Chinese scientists published a draft [[genome]] of ''Ginkgo biloba'' in 2016.<ref name="Guan-2016">{{cite journal |last1=Guan |first1=Rui |last2=Zhao |first2=Yunpeng |last3=Zhang |first3=He |last4=Fan |first4=Guangyi |last5=Liu |first5=Xin |last6=Zhou |first6=Wenbin |last7=Shi |first7=Chengcheng |last8=Wang |first8=Jiahao |last9=Liu |first9=Weiqing |date=1 January 2016 |title=Draft genome of the living fossil Ginkgo biloba |journal=GigaScience |volume=5 |issue=1 |page=49 |doi=10.1186/s13742-016-0154-1 |pmid=27871309 |pmc=5118899 |issn=2047-217X |doi-access=free }}</ref> The tree has a large genome of 10.6&nbsp;billion [[DNA]] [[nucleobase]] "letters" (the human genome has three billion) and about 41,840&nbsp;predicted [[gene]]s<ref>{{cite news |url=https://www.bbc.com/news/science-environment-38057741 |title=Ginkgo 'living fossil' genome decoded |date=21 November 2016 |newspaper=BBC News |language=en-GB |access-date=23 November 2016}}</ref> which enable a considerable number of antibacterial and chemical defense mechanisms.<ref name="Guan-2016"/> 76.58% of the assembled sequence turned out to be repetitive sequences.<ref>[https://gigascience.biomedcentral.com/articles/10.1186/s13742-016-0154-1 Draft genome of the living fossil Ginkgo biloba – GigaScience]</ref>

In 2020, a study in China of [[ginkgo]] trees up to 667 years old showed little effects of aging, finding that the trees continued to grow with age and displayed no genetic evidence of [[senescence]], and continued to make [[phytochemical]]s indefinitely.<ref name=cnn>{{cite news |last=Hunt |first=Katie |date=January 14, 2020 |title=Some trees can live for more than 1,000 years and scientists may have figured out why |work=[[CNN]] |url=https://www.cnn.com/2020/01/14/asia/ginkgo-trees-secret-longevity-scn/index.html |access-date=January 19, 2020}}</ref>

=== Phytochemicals ===
Extracts of ginkgo leaves contain [[phenolic acid]]s, [[proanthocyanidin]]s, [[glycoside#Flavonoid glycosides|flavonoid glycoside]]s, such as [[myricetin]], [[kaempferol]], [[isorhamnetin]], and [[quercetin]], and the [[terpene]] trilactones [[ginkgolide]]s and [[bilobalide]]s.<ref name=drugs/><ref>{{cite journal |journal=Journal of Chromatography A |year=2002 |volume=967 |issue=1 |pages=21–55 |title=Chemical analysis of Ginkgo biloba leaves and extracts |vauthors=van Beek TA |doi=10.1016/S0021-9673(02)00172-3 |pmid=12219929}}</ref><ref name="vb2">{{cite journal |journal=J Chromatogr A |year=2009 |volume=1216 |issue=11 |pages=2002–2032 |doi=10.1016/j.chroma.2009.01.013 |pmid=19195661 |title=Chemical analysis and quality control of Ginkgo biloba leaves, extracts, and phytopharmaceuticals |vauthors=van Beek TA, Montoro P}}</ref> The leaves also contain unique ginkgo [[biflavone]]s, [[alkylphenol]]s, and [[polyprenol]]s.<ref name=vb2/>