Biology:Camellia sinensis

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Short description: Species of evergreen shrub

Camellia sinensis
Csinensis.jpg
Tea Bud.jpg
Camellia sinensis foliage
Scientific classification edit
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Ericales
Family: Theaceae
Genus: Camellia
Species:
C. sinensis
Binomial name
Camellia sinensis
(L.) Kuntze
Tea plants native range.jpg
Native range of Camellia sinensis
Synonyms[2]

Camellia sinensis is a species of evergreen shrub or small tree in the flowering plant family Theaceae. Its leaves, leaf buds, and stems can be used to produce tea. Common names include tea plant, tea shrub, and tea tree (unrelated to Melaleuca alternifolia, the source of tea tree oil, or the genus Leptospermum commonly called tea tree).

White tea, yellow tea, green tea, oolong, dark tea (which includes pu-erh tea) and black tea are all harvested from one of two major varieties grown today, C. sinensis var. sinensis and C. s. var. assamica,[3] but are processed differently to attain varying levels of oxidation with black tea being the most oxidized and green being the least.[4] Kukicha (twig tea) is also harvested from C. sinensis, but uses twigs and stems rather than leaves.

Description

Camellia sinensis is native to East Asia, the Indian Subcontinent, and Southeast Asia, but it is today cultivated all around the world in tropical and subtropical regions. It is an evergreen shrub or small tree that is usually trimmed to below 2 m (6.6 ft) when cultivated for its leaves. It has a strong taproot. The flowers are yellow-white, 2.5–4 cm (0.98–1.57 in) in diameter, with seven or eight petals.

Flower of tea plant
Pollen grains of C. sinensis

The seeds of C. sinensis and C. oleifera can be pressed to yield tea oil, a sweetish seasoning and cooking oil that should not be confused with tea tree oil, an essential oil that is used for medical and cosmetic purposes, and originates from the leaves of a different plant.

C. sinensis plant, with cross-section of the flower (lower left) and seeds (lower right)
C. sinensis

The leaves are 4–15 cm (1.6–5.9 in) long and 2–5 cm (0.79–1.97 in) broad. Fresh leaves contain about 4% caffeine, as well as related compounds including theobromine.[5] The young, light-green leaves are preferably harvested for tea production when they have short, white hairs on the underside. Older leaves are deeper green. Different leaf ages produce differing tea qualities, since their chemical compositions are different. Usually, the tip (bud) and the first two to three leaves are harvested for processing. This hand picking is repeated every one to two weeks.

In 2017, Chinese scientists sequenced the genome of C. s. var. assamica.[6] It contains about three billion base pairs, which was larger than most plants previously sequenced.[7]

Taxonomy

The generic name Camellia is taken from the Latinized name of Rev. Georg Kamel,[8] SJ (1661–1706), a Moravian-born Jesuit lay brother, pharmacist, and missionary to the Philippines .

Carl Linnaeus chose his name in 1753 for the genus to honor Kamel's contributions to botany[9] (although Kamel did not discover or name this plant, or any Camellia,[10] and Linnaeus did not consider this plant a Camellia but a Thea).[11]

Robert Sweet shifted all formerly Thea species to the genus Camellia in 1818.[12] The name sinensis means "from China" in Latin.

Four varieties of C. sinensis are recognized.[2] Of these, C. sinensis var. sinensis and C. s. var. assamica (JW Masters) Kitamura are most commonly used for tea, and C. s. var. pubilimba Hung T. Chang and C. s. var. dehungensis (Hung T. Chang & BH Chen) TL Ming are sometimes used locally.[2] The Cambodia type tea (C. assamica subsp. lasiocaly) was originally considered a type of assam tea. However, later genetic work showed that it is a hybrid between Chinese small leaf tea and assam type tea.[13]

Tea plants are native to East Asia, and probably originated in the borderlands of north Burma and southwestern China.[14]

  • Chinese (small leaf) tea [C. sinensis var. sinensis]
  • Chinese Western Yunnan Assam (large leaf) tea [C. sinensis var. assamica]
  • Indian Assam (large leaf) tea [C. sinensis var. assamica]
  • Chinese Southern Yunnan Assam (large leaf) tea [C. sinensis var. assamica]

Chinese (small leaf) tea may have originated in southern China possibly with hybridization of unknown wild tea relatives. However, since no wild populations of this tea are known, the precise location of its origin is speculative.[15][16]

Given their genetic differences forming distinct clades, Chinese Assam type tea (C. s. var. assamica) may have two different parentages – one being found in southern Yunnan (Xishuangbanna, Pu'er City) and the other in western Yunnan (Lincang, Baoshan). Many types of Southern Yunnan Assam tea have been hybridized with the closely related species Camellia taliensis. Unlike Southern Yunnan Assam tea, Western Yunnan Assam tea shares many genetic similarities with Indian Assam type tea (also C. s. var. assamica). Thus, Western Yunnan Assam tea and Indian Assam tea both may have originated from the same parent plant in the area where southwestern China, Indo-Burma, and Tibet meet. However, as the Indian Assam tea shares no haplotypes with Western Yunnan Assam tea, Indian Assam tea is likely to have originated from an independent domestication. Some Indian Assam tea appears to have hybridized with the species Camellia pubicosta.[15][16]

Assuming a generation of 12 years, Chinese small leaf tea is estimated to have diverged from Assam tea around 22,000 years ago; this divergence would correspond to the last glacial maximum,[15][16] while Chinese Assam tea and Indian Assam tea diverged 2,800 years ago.

Chinese small leaf type tea was introduced into India in 1836 by the British and some Indian Assam type tea (e.g. Darjeeling tea) appear to be genetic hybrids of Chinese small leaf type tea, native Indian Assam, and possibly also closely related wild tea species.[17]

Cultivars

Hundreds,[18] if not thousands of cultivars of C. sinensis are known. Some Japanese cultivars include:

Cultivation

Camellia sinensis is mainly cultivated in tropical and subtropical climates, in areas with at least 127 cm (50 in) of rainfall a year. Tea plants prefer a rich and moist growing location in full to part sun, and can be grown in hardiness zones 7–9. However, the clonal one is commercially cultivated from the equator to as far north as Cornwall and Scotland on the UK mainland.[21][22] Many high quality teas are grown at high elevations, up to 2,200 m (7,200 ft), as the plants grow more slowly and acquire more flavor.

Tea plants will grow into a tree if left undisturbed, but cultivated plants are pruned to waist height for ease of plucking. Two principal varieties are used, the small-leaved Chinese variety plant (C. s. sinensis) and the large-leaved Assamese plant (C. s. assamica), used mainly for black tea.

Chinese teas

The Chinese plant is a small-leafed bush with multiple stems that reaches a height of some 3 m (9.8 ft). It is native to southeast China. The first tea plant variety to be discovered, recorded, and used to produce tea dates back 3,000 years ago; it yields some of the most popular teas.

C. s. var. waldenae was considered a different species, C. waldenae by SY Hu,[23] but it was later identified as a variety of C. sinensis.[24] This variety is commonly called Waldenae Camellia. It is seen on Sunset Peak and Tai Mo Shan in Hong Kong. It is also distributed in the Guangxi province.[23]

Indian teas

Three main kinds of tea are produced in India:

  • Assam, from the var. assamica plant, comes from the near sea-level heavily forested northeastern section of India, the state of Assam. Tea from here is rich and full-bodied. The first tea estate in India was established in Assam in 1837. Teas are manufactured in either the orthodox process or the CTC process.
  • Darjeeling, from the var. sinensis plant, is from the cool and wet Darjeeling highland region, tucked in the foothills of the Himalayas. Tea plantations could be at altitudes as high as 2,200 m (7,200 ft). The tea is delicately flavored, and considered to be one of the finest teas in the world. The Darjeeling plantations have three distinct harvests, termed 'flushes', and the tea produced from each flush has a unique flavor. First (spring) flush teas are light and aromatic, while the second (summer) flush produces tea with a bit more bite. The third, or autumn flush gives a tea that is lesser in quality.
  • Nilgiri is from a southern region of India almost as high as Darjeeling. Grown at elevations between 1,000 and 2,500 m (3,300 and 8,200 ft), Nilgiri teas are subtle and rather gentle, and are frequently blended with other, more robust teas.[citation needed]
Seed-bearing fruit of C. sinensis

Pests and diseases

Main page: Biology:List of tea diseases

Tea leaves are eaten by some herbivores, such as the caterpillars of the willow beauty (Peribatodes rhomboidaria), a geometer moth.

Health effects

Although health benefits have been assumed throughout the history of using tea as a common beverage, no high-quality evidence shows that tea confers significant benefits.[25][26] In clinical research over the early 21st century, tea has been studied extensively for its potential to lower the risk of human diseases, but none of this research is conclusive as of 2017.[25]

Biosynthesis of caffeine

Caffeine, a molecule produced in C. sinensis, functions as a secondary metabolite and acts as a natural pesticide: it can paralyze and kill herbivorous insects feeding on the plant.[27] Caffeine is a purine alkaloid and its biosynthesis occurs in young tea leaves and is regulated by several enzymes.[28][29] The biosynthetic pathway in C. sinensis is similar to other caffeine-producing plants such as coffee or guayusa.[30] Analysis of the pathway was carried out by harvesting young leaves and using reverse transcription PCR to analyze the genes encoding the major enzymes involved in synthesizing caffeine. The gene TCS1 encodes caffeine synthase. Younger leaves feature high concentrations of TCS1 transcripts, allowing more caffeine to be synthesized during this time. Dephosphorylation of xanthosine-5'-monophosphate into xanthosine is the committed step for the xanthosines entering the beginning of the most common pathway. A sequence of reactions turns xanthosine (9β-D-ribofuranosylxanthine) into 7-methylxanthosine, then 7-methylxanthine, then theobromine (3,7-dimethylxanthine), and finally into caffeine (1,3,7-trimethylxanthine).

Biochemical pathway detailing caffeine synthesis in C. sinensis

See also


Primary green tea catechins

References

  1. ↑ Rivers, M.C.; Wheeler, L. (2018). "Camellia sinensis". IUCN Red List of Threatened Species 2018: e.T62037625A62037628. doi:10.2305/IUCN.UK.2018-1.RLTS.T62037625A62037628.en. https://www.iucnredlist.org/species/62037625/62037628. Retrieved 19 November 2021. 
  2. ↑ 2.0 2.1 2.2 Min, Tianlu; Bartholomew, Bruce. "18. Theaceae". Flora of China. 12. http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200014043. Retrieved 16 October 2011. 
  3. ↑ ITIS Standard Report Page Camellia Sinensis retrieved 2009-03-28.
  4. ↑ Preedy, V.R. (2013). Tea in Health and Disease Prevention. Elsevier Science. pp. 199–200. ISBN 978-0-12-384937-3. https://books.google.com/books?id=k3HK2WuZrsYC. Retrieved February 24, 2022. 
  5. ↑ "Camellia sinensis". Purdue. http://www.hort.purdue.edu/newcrop/duke_energy/Camellia_sinensis.html. 
  6. ↑ "The Tea Tree Genome Provides Insights into Tea Flavor and Independent Evolution of Caffeine Biosynthesis". Molecular Plant 10 (6): 866–877. June 2017. doi:10.1016/j.molp.2017.04.002. PMID 28473262. 
  7. ↑ Briggs, Helen (2017-05-02). "Secrets of tea plant revealed by science" (in en-GB). BBC News. https://www.bbc.co.uk/news/science-environment-39747720. 
  8. ↑ Taxonomic literature: A selective guide to botanical publications and collections with dates, commentaries and types (2nd ed.). Utrecht: Bohn, Scheltema and Holkema. 1976–1988. ISBN 978-9031302246. https://archive.org/details/taxonomicliterat41983staf. 
  9. ↑ "Botanics", History of Tea, 10 August 2003, http://www.gol27.com/HistoryTeaBotanics.html, retrieved 5 February 2012, "Georg Jeoseph Kamel, whose name in Latin was Camellus was missionary to the Philippines, died in Manilla in 1706. […] Camellias were named in posthumous honor of George Joseph Kamel by Carolus Linnæus" .
  10. ↑ "Botanics", History of Tea, 10 August 2003, http://www.gol27.com/HistoryTeaBotanics.html, retrieved 5 February 2012, "It is speculated that he never saw a camellia" .
  11. ↑ Golender, Leonid (10 August 2003), "Botanics", History of Tea, http://www.gol27.com/HistoryTeaBotanics.html, retrieved 5 February 2012, "The first edition of Linnaeus's Species Plantarum published in 1753 suggested calling the tea plant Thea sinensis..." 
  12. ↑ International Association for Plant Taxonomy (2006), "Article 13, example 3", International Code of Botanical Nomenclature (Vienna Code) (electronic ed.), http://www.bgbm.fu-berlin.de/iapt/nomenclature/code/tokyo-e/Art_13.htm, retrieved 5 February 2012, "The generic names Thea L. (Sp. Pl.: 515. 24 Mai 1753), and Camellia L. (Sp. Pl.: 698. 16 August 1753; Gen. Pl., ed. 5: 311. 1754), are treated as having been published simultaneously on 1 May 1753. … the combined genus bears the name Camellia, since Sweet (Hort. Suburb. Lond.: 157. 1818), who was the first to unite the two genera, chose that name, and cited Thea as a synonym" .
  13. ↑ Wambulwa, MC, MK Meegahakumbura, R Chalo, et al. 2016. Nuclear microsatellites reveal the genetic architecture and breeding history of tea germplasm of East Africa. Tree Genetics & Genomes, 12.
  14. ↑ Yamamoto, T; Kim, M; Juneja, L R (1997). Chemistry and Applications of Green Tea. CRC Press. p. 4. ISBN 978-0-8493-4006-2. "For a long time, botanists have asserted the dualism of tea origin from their observations that there exist distinct differences in the morphological characteristics between Assamese varieties and Chinese varieties... Hashimoto and Shimura reported that the differences in the morphological characteristics in tea plants are not necessarily the evidence of the dualism hypothesis from the researches using the statistical cluster analysis method. In recent investigations, it has also been made clear that both varieties have the same chromosome number (n=15) and can be easily hybridised with each other. In addition, various types of intermediate hybrids or spontaneous polyploids of tea plants have been found in a wide area extending over the regions mentioned above. These facts may prove that the place of origin of Camellia sinensis is in the area including the northern part of the Burma, Yunnan, and Sichuan districts of China." 
  15. ↑ 15.0 15.1 15.2 Meegahakumbura, MK et al. (2016). "Indications for three independent domestication events for the tea plant (Camellia sinensis (L.) O. Kuntze) and new insights into the origin of tea germplasm in China and India revealed by nuclear microsatellites". PLOS ONE 11 (5): e0155369. doi:10.1371/journal.pone.0155369. PMID 27218820. Bibcode: 2016PLoSO..1155369M. 
  16. ↑ 16.0 16.1 16.2 "Domestication origin and breeding history of the tea plant (Camellia sinensis) in China and India based on nuclear microsatellites and cpDNA sequence data". Frontiers in Plant Science 8: 2270. 2018. doi:10.3389/fpls.2017.02270. PMID 29422908. 
  17. ↑ Wambulwa, M. C.; Meegahakumbura, M. K.; Chalo, R.; Kamunya, S.; Muchugi, A.; Xu, J. C.; Liu, J.; Li, D. Z. et al. (2016). "Nuclear microsatellites reveal the genetic architecture and breeding history of tea germplasm of East Africa". Tree Genetics & Genomes 12 (1): 11. doi:10.1007/s11295-015-0963-x. 
  18. ↑ "Tea Cultivar Database – World of Tea" (in en-US). World of Tea. https://worldoftea.org/cultivar-database/. 
  19. ↑ 19.0 19.1 "Identification of Japanese tea (Camellia sinensis) cultivars using SSR marker". Food and Agriculture Organization. http://agris.fao.org/agris-search/search.do?recordID=JP2008002305. 
  20. ↑ 20.0 20.1 20.2 20.3 20.4 "Varietal differences in the adaptability of tea [Camellia sinensis cultivars to light nitrogen application"]. Food and Agriculture Organization. http://agris.fao.org/agris-search/search.do?recordID=JP2008003777. 
  21. ↑ "English tea service", Telegraph, 17 September 2005, https://www.telegraph.co.uk/gardening/main.jhtml?xml=/gardening/2005/09/17/gtea17.xml, retrieved 19 June 2021 .
  22. ↑ "The world's first Scottish tea (at £10 a cup)", The Independent, 17 November 2014, https://www.independent.co.uk/life-style/food-and-drink/features/the-worlds-first-scottish-tea-at-10-a-cup-9866437.html, retrieved 25 August 2017 .
  23. ↑ 23.0 23.1 The International Camellia Society (ICS), DE: Uniklinik Sårland, http://www.uniklinik-saarland.de/med_fak/physiol2/camellia/register/species/spec_rs.htm 
  24. ↑ "A revision of Camellia sect. Thea" (in Chinese). Acta Botanica Yunnanica 14 (2): 115–132. 1992. .
  25. ↑ 25.0 25.1 "Black tea". MedlinePlus, US National Library of Medicine. 30 November 2017. https://www.nlm.nih.gov/medlineplus/druginfo/natural/997.html. 
  26. ↑ "Green tea". National Center for Complementary and Integrative Health, US National Institutes of Health. 30 November 2016. https://nccih.nih.gov/health/greentea. 
  27. ↑ "Caffeine and related methylxanthines: possible naturally occurring pesticides". Science 226 (4671): 184–187. October 1984. doi:10.1126/science.6207592. PMID 6207592. Bibcode: 1984Sci...226..184N. 
  28. ↑ "Expression of caffeine biosynthesis genes in tea (Camellia sinensis)". Zeitschrift für Naturforschung C 63 (3–4): 267–270. March 2008. doi:10.1515/znc-2008-3-417. PMID 18533472. 
  29. ↑ "Purification and characterization of caffeine synthase from tea leaves". Plant Physiology 120 (2): 579–586. June 1999. doi:10.1104/pp.120.2.579. PMID 10364410. 
  30. ↑ Lin, Zhipeng; Wei, Jian; Hu, Yongqiang; Pi, Dujuan; Jiang, Mingguo; Lang, Tao (January 2023). "Caffeine Synthesis and Its Mechanism and Application by Microbial Degradation, A Review" (in en). Foods 12 (14): 2721. doi:10.3390/foods12142721. ISSN 2304-8158. PMID 37509813. 
  31. ↑ Textbook of Natural Medicine (4th ed.). Edinburgh: Churchill Livingstone. 2012. p. 628. ISBN 978-1-4377-2333-5. 

External links


Wikidata ☰ Q101815 entry



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