Ginkgo biloba

, Belgium Ginkgos are large trees, normally reaching a height of , with some specimens in China being over 40 meters (131 feet). The tree has an angular 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 roots and sprouts makes ginkgos durable, with some specimens estimated to be more than 3,500 years old. Leaves 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. Two veins enter the leaf blade at the base and fork repeatedly in two; this is known as dichotomous venation. The leaves are usually , but sometimes up to long. The old common name, maidenhair tree, derives from the leaves resembling pinnae of the maidenhair fern, Adiantum capillus-veneris. Ginkgos are prized for their autumn foliage, which is a deep saffron yellow. The species is heterophyllous (two types of leaves); those on the long shoots are thicker, have higher rates of photosynthesis, higher vein density and leaf hydraulic conductance, while those on the short shoots are better at handling drought. Leaves of long shoots are also 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 and have stomata on both sides. During autumn, the leaves turn a bright yellow and then fall, sometimes within a short space of time (one to fifteen days). Leaves of the cultivar 'Tubifolia' have funnel-shaped leaves. Branches Ginkgo branches grow in length by growth of shoots with regularly spaced leaves, as seen on most trees. From the axils of these leaves, "spur shoots" (also known as short shoots) develop on second-year growth. Short shoots have short internodes (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. 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 Mountains, 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 (lignotubers, 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 Tianmushan, 40% of the specimens surveyed were multi-stemmed, and few saplings were present. Reproduction Ginkgo biloba is dioecious, with separate sexes, some trees being female and others being male. Male plants produce small pollen cones with sporophylls, each bearing two microsporangia spirally arranged around a central axis. Sex conversion, wherein certain branches of a tree change sexes, has been observed. 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. Female plants do not produce cones. Two ovules are formed at the end of a stalk. Pollination Fertilization of the ovule occurs through wind pollination, via motile sperm, as in cycads, ferns, mosses, and algae. The sperm are large (about 70–90 micrometres) 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. 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 ovules, and development of the embryos, occurs just before or after they fall from the tree in early autumn . Fruiting and Dispersal After fertilization, one or both ovules develop into fruit-like structures containing seeds. The fruits are 1.5–2 cm long, with a soft, fleshy, yellow-brown outer layer (the sarcotesta) that is attractive in appearance, but contains butyric acid (also known as butanoic acid) and smells foul like rancid butter or vomit 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. Despite its perception by humans as foul, the fruit odor is attractive to certain small mammals that eat the fruit and disperse the seeds: these include the gray squirrel and, in East Asia, the palm civet and the raccoon dog . The sclerotesta resists digestion, and so the seeds are passed intact into feces, which thus provide a dispersal mechanism. Genome Chinese scientists published a draft genome of Ginkgo biloba in 2016. The tree has a large genome of 10.6 billion DNA nucleobase "letters" (the human genome has three billion) and about 41,840 predicted genes which enable a considerable number of antibacterial and chemical defense mechanisms. 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 phytochemicals indefinitely. Phytochemicals Extracts of ginkgo leaves contain phenolic acids, proanthocyanidins, flavonoid glycosides, such as myricetin, kaempferol, isorhamnetin, and quercetin, and the terpene trilactones ginkgolides and bilobalides. The leaves also contain unique ginkgo biflavones, alkylphenols, and polyprenols. == Taxonomy ==

Carl Linnaeus described the species in 1771, the specific epithet biloba derived from the Latin bis, "twice" and loba, "lobed", referring to the shape of the leaves. Two names for the species recognise the botanist Richard Salisbury, a placement by Nelson as Pterophyllus salisburiensis and the earlier Salisburia adiantifolia proposed by James Edward Smith. The epithet of the latter may have been intended to denote a characteristic resembling Adiantum, the genus of maidenhair ferns. The scientific name Ginkgo can be traced to the end of the 17th century. Kanji typically have multiple pronunciations in Japanese, and the characters used for ginnan can also be pronounced ginkyō. Engelbert Kaempfer, the first Westerner to investigate the species in 1690 in Nagasaki, wrote down the tree name in the notes that he later used for the Amoenitates Exoticae (1712) with the spelling "ginkgo". Taking his spelling of other Japanese words containing the syllable "kyō" into account, a usual romanization following his writing habits should have been "ginkio" or "ginkjo". showed that it was the spelling of his interpreter, Genemon Imamura, who spoke the dialect of Nagasaki.. Linnaeus, who relied on Kaempfer when dealing with Japanese plants, adopted the spelling given in Kaempfer's "Flora Japonica" (Amoenitates Exoticae, p. 811). Kaempfer's drawing can be found in Hori's article. Classification The relationship of ginkgo to other plant groups remains uncertain. It has been placed loosely in the divisions Spermatophyta and Pinophyta, but no consensus has been reached. Since its seeds are not protected by an ovary wall, it can morphologically be considered a gymnosperm. The apricot-like structures produced by female ginkgo trees are technically not fruits, but are seeds that have a shell consisting of a soft and fleshy section (the sarcotesta), and a hard section (the sclerotesta). The sarcotesta has a strong smell that most people find unpleasant. The ginkgo is classified in its own division, the Ginkgophyta, comprising the single class Ginkgoopsida, order Ginkgoales, family Ginkgoaceae, genus Ginkgo and is the only extant species within this group. It is one of the best-known examples of a living fossil, because Ginkgoales other than G. biloba are not known from the fossil record after the Pliocene. File:Ginkgo yimaensis.jpg|Extinct Ginkgo yimaensis File:Ginkgo apodes.jpg|Extinct G. apodes The closest living relatives of the clade are the cycads, Rise and decline epoch from the McAbee Fossil Beds, British Columbia Fossils attributable to the genus Ginkgo first appeared in the Middle Jurassic. The genus Ginkgo diversified and spread throughout Laurasia during the Jurassic and Early Cretaceous. While it may seem improbable that a single species may exist as a contiguous entity for many millions of years, many of the ginkgo's life-history parameters fit: Extreme longevity; slow reproduction rate; (in Cenozoic and later times) a wide, apparently contiguous, but steadily contracting distribution; and (as far as can be demonstrated from the fossil record) extreme ecological conservatism (restriction to disturbed streamside environments). The genus name is regarded as a misspelling of the Japanese pronunciation () reading the aforementioned kanji found in Chinese herbology literature such as (Daily Use Materia Medica) (1329) and Compendium of Materia Medica published in 1578. Despite its spelling, which is due to a complicated etymology including a transcription error, "ginkgo" is usually pronounced , which has given rise to the common alternative spelling "gingko". The spelling pronunciation is also documented in some dictionaries. Engelbert Kaempfer first introduced the spelling ginkgo in his book of 1712. It is considered that he may have misspelled "Ginkjo" or "Ginkio" (both consistent with his treatment of Japanese in the same work) as "Ginkgo". This misspelling was included by Linnaeus in his book and has become the name of the tree's genus. The specific epithet is New Latin for "two-lobed". ==Distribution and habitat==

Although Ginkgo biloba and other species of the genus were once widespread throughout the world, its habitat had shrunk by two million years ago. For centuries, it was thought to be extinct in the wild, but is now a common tree cultivated throughout eastern China, Korea, and Japan. Many municipalities in China, Korea and Japan use ginkgos as street trees, and ginkgo leaves are the emblem of prominent educational institutions such as the University of Tokyo and Sungkyunkwan University in South Korea. Despite their widespread habitat, high genetic uniformity exists among ginkgo trees, with some Chinese scholars suggesting that ginkgo trees in these areas may have been planted and preserved by Chinese monks over about 1,000 years. A study demonstrates a greater genetic diversity in Southwestern China populations, supporting glacial refugia in mountains surrounding the eastern Tibetan Plateau, where several old-growth candidates for wild populations have been reported. Whether native ginkgo populations still exist has not been demonstrated unequivocally, but there is genetic evidence that these Southwestern populations may be wild, as well as evidence that the largest and oldest G. biloba trees may be older than surrounding human settlements. While cultivated specimens can survive in a variety of environments (such as a subtropical climate), the wild ginkgo is native to areas with a mostly temperate climate. ==Ecology==

Gingko biloba is the only vascular plant known to host a microalga, a Cocomyxa-like green alga, as an endosymbiont. This symbiosis is vertically inherited and present worldwide. The endosymbiont has been found in gingkos in Asia, North America, and Europe. Photosynthetic activity does not occur as the algae are hosted intracellularly in an immature "precursor" form without a functional chloroplast. The endosymbiotic algae may be involved in metabolic pathways of the gingko host. ==Cultivation==

Park, Belgium Ginkgo has long been cultivated in China. It is common in the southern third of the country. in both areas, some naturalization has occurred, with ginkgos seeding into natural forests. Ginkgo has been commonly cultivated in North America for over 200 years and in Europe for close to 300, but during that time, it has never become significantly naturalized. G. biloba is also commonly manually planted in cities across the United States and Europe. This species is highly tolerant to pollution and serves as a visually appealing, shade-providing tree in many cities and gardens. Many intentionally planted ginkgos are male cultivars grafted onto plants propagated from seed, because the male trees will not produce the malodorous seeds. The popular cultivar 'Autumn Gold' is a clone of a male plant. The disadvantage of male Ginkgo biloba trees is that their pollen is highly allergenic. They have an OPALS (Ogren Plant Allergy Scale) rating of 7 (out of 10), whereas female trees, which can produce no pollen, have an OPALS allergy scale rating of 2. Female cultivars include 'Liberty Splendor', 'Santa Cruz', and 'Golden Girl', the latter so named because of the striking yellow color of its leaves in the fall; all female cultivars release zero pollen. They rarely have disease problems, even in urban conditions, and are attacked by few insects. Ginkgos are popular subjects for growing as miniature landscapes known as penjing and bonsai; they can be kept artificially small and tended over centuries. The trees are easy to propagate from seed. Hiroshima Extreme examples of the ginkgo's tenacity may be seen in Hiroshima, Japan, where six trees growing between from the 1945 atom bomb explosion were among the few living organisms in the area to survive the blast. Although almost all other plants (and animals) in the area were killed, the ginkgos, though charred, survived and were soon healthy again, among other hibakujumoku (trees that survived the blast). The six trees are still alive. They are marked with signs at temple (planted in 1850), Shukkei-en (planted about 1740), Jōsei-ji (planted 1900), at the former site of Senda Elementary School near Miyukibashi, at the Myōjōin temple, and an Edo period-cutting at Anraku-ji temple. 1000-year-old ginkgo at Tsurugaoka Hachimangū At the Tsurugaoka Hachiman-gū's shrine in the city of Kamakura, Kanagawa Prefecture, Japan, an ancient ginkgo tree stands beside the stone entry staircase. According to legend, the tree has stood there since the founding of the shrine circa 1063. The tree is nicknamed kakure-ichō (hiding ginkgo), because of an Edo period legend in which shōgun Minamoto no Sanetomo was assassinated in 1219 by his nephew, Kugyō, who had hidden behind the tree to ambush the shōgun. On 10 March 2010, the tree blew down in a storm, but the stump has since sprouted vigorously. The tree itself is a popular tourist attraction. ==Toxicity==

Since 2016, G. biloba extract is classified as a possible human carcinogen (group 2B) by the International Agency for Research on Cancer. When eaten in large quantities or over a long period, the seeds may cause poisoning by ginkgotoxin (4'-O-methylpyridoxine, MPN), as found in a few case reports. A heat-stable compound not destroyed by cooking, MPN may cause convulsions, which were alleviated by treatment with pyridoxine phosphate (vitamin B6), according to limited studies. or blisters similar to that caused by contact with poison ivy. Side effects of using ginkgo supplements may include increased risk of bleeding, gastrointestinal discomfort, nausea, vomiting, diarrhea, headaches, dizziness, heart palpitations, and restlessness. Although use of standardized Ginkgo biloba leaf extracts in moderate amounts appears to be safe, Ginkgo pollen may produce allergic reactions. which are highly allergenic long-chain alkylphenols, such as bilobol or adipostatin A (bilobol is a substance related to anacardic acid from cashew nut shells and urushiols present in poison ivy and other Toxicodendron spp.) == Uses ==

The wood of Ginkgo biloba is used to make furniture, chessboards, carving, and casks for making saké; the wood is fire-resistant and slow to decay. In Korea, ginkgo nuts are stir-fried and eaten, or are used to garnish foods such as sinseonro. Research and safety Although extracts of G. biloba leaf are often marketed as cognitive enhancers, there is no evidence for effects on memory or attention in healthy people. Systematic reviews have shown there is no evidence for effectiveness of ginkgo extract in treating high blood pressure, menopause-related cognitive decline, tinnitus, post-stroke recovery, or altitude sickness. G. biloba and its extracts are not approved as a drug in the United States and do not have sufficient clinical evidence for uses as a therapy, according to a 2023 review. The United States National Center for Complementary and Integrative Health concludes that despite extensive research, ginkgo has not been conclusively proved as effective for any health condition, including dementia, cognitive decline, or other disorders for which it is commonly marketed. A 2018 review concluded that 22- to 24-week treatment with a G. biloba extract improved behavioral and psychological symptoms of dementia, and reduced caregiver distress compared to placebo. A 2017 overview of systematic reviews concluded that G. biloba extract may modestly improve cognitive function and daily living in dementia when taken at doses over 200 mg per day for at least 22 weeks. A 2016 systematic review concluded that G. biloba extract reduced tardive dyskinesia symptoms in people with schizophrenia and is generally safe. In 2014, the Committee on Herbal Medicinal Products of the European Medicines Agency concluded that powdered ginkgo leaf extract is effective and safe for improving cognitive function and quality of life in people with mild dementia, listing it as an herbal medicine in member states of the EU. FDA warning letters Over the period 2021–2023, the US FDA issued warning letters to manufacturers of ginkgo dietary supplements for false advertising about health claims and misbranding of their products as non-approved drugs. Traditional medicine Ginkgo has been used in traditional Chinese medicine since at least the 11th century CE. Ginkgo seeds, leaves, and nuts have traditionally been used to treat various ailments, such as dementia, asthma, bronchitis, and kidney and bladder disorders. However, there is no conclusive evidence that ginkgo is useful for any of these conditions. ==In culture==

, Japan's capital, representing a ginkgo leaf The ginkgo leaf is the symbol of the Urasenke school of Japanese tea ceremony. The tree is the official tree of the Japanese capital of Tokyo, and the symbol of Tokyo is a ginkgo leaf. Since 1948, the badge of Tokyo University has been two ginkgo leaves (designed by Shoichi Hoshino), which became the university logo in 2004 with a redesign. The logo of Osaka University has been a simplified ginkgo leaf since 1991 when designer Ikko Tanaka created it for the university's sixtieth anniversary. In professional sumo, wrestlers ranked in the two highest divisions ( and ) wear an elaborate topknot called because it resembles the leaf of the ginkgo tree. Ginkgo is an official tree of Seoul since 1971, designated by the Seoul Metropolitan Government. ==Gallery==

File:Ginkgo Tree Ginkgo biloba Trunk Bark 2000px.jpg|Trunk bark File:Ginkgo-biloba-male.JPG|Ginkgo pollen-bearing cones File:Ginko bud.jpg|Bud in spring File:GingkoFruitingTwigSpring.jpg|Ovules ready for fertilization File:Ginkgo embryo and gametophyte.jpg|Female gametophyte, dissected from a seed freshly shed from the tree, containing a well-developed embryo File:Ginkgo biloba0.jpg|Immature ginkgo ovules and leaves File:Gingko fg01.jpg|Autumn leaves and fallen seeds File:GinkgoSaplings.jpg|A forest of saplings sprout among last year's seeds File:2014-11-02 12 06 44 Ginkgo during autumn at the Ewing Presbyterian Church Cemetery in Ewing, New Jersey.jpg|Ginkgo tree in autumn File:Shojokoji - Kanagawa - 2025 12 1.ogg|thumbtime=8|A large ginkgo tree at a temple in Kanagawa, Japan File:Ginko biloba leaves.jpg|Ginkgo biloba leaves File:HUEB in Fall.jpg|Several golden ginkgos in Hebei, China File:03-Stack 176 Ginkgo 40x obj leaf print.jpg|Leaf print showing sunken stomata on leaf underside ==See also==