Camellia sinensis is a species of evergreen shrub or small tree whose leaves and leaf buds are used to produce tea. It is of the genus Camellia (Chinese: ??; pinyin: Cháhu?, literally: "tea flower") of flowering plants in the family Theaceae. Common names include "tea plant", "tea shrub", and "tea tree" (not to be confused with Melaleuca alternifolia, the source of tea tree oil, or Leptospermum scoparium, the M?nuka or New Zealand Teatree from which M?nuka Honey is derived).
Camellia sinensis var. sinensis and its subspecies, Camellia sinensis var. assamica, are two major varieties grown today. White tea, yellow tea, green tea, oolong, dark tea (which includes pu-erh tea) and black tea are all harvested from one or the other, but are processed differently to attain varying levels of oxidation. Kukicha (twig tea) is also harvested from Camellia sinensis, but uses twigs and stems rather than leaves.
Video Camellia sinensis
Nomenclature and taxonomy
The name Camellia is taken from the Latinized name of Rev. Georg Kamel, 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 (although Kamel did not discover or name this plant, or any Camellia, and Linnaeus did not consider this plant a Camellia but a Thea).
Robert Sweet shifted all formerly Thea species to the genus Camellia in 1818. The name sinensis means "from China" in Latin.
Four varieties of Camellia sinensis are recognized. Of these, C. sinensis var. sinensis and C. sinensis var. assamica (JW Masters) Kitamura are most commonly used for tea, and C. sinensis var. pubilimba Hung T. Chang and C. sinensis var. dehungensis (Hung T. Chang & BH Chen) TL Ming are sometimes used locally.
Maps Camellia sinensis
Cultivars
There are hundreds, if not thousands of cultivars of C. sinensis. Some Japanese cultivars include:
- Benifuuki
- Fushun
- Kanayamidori
- Meiryoku
- Saemidori
- Okumidori
- Yabukita
Description
Camellia sinensis is native to East Asia, the Indian Subcontinent and Southeast Asia, but it is today cultivated across the world in tropical and subtropical regions.
Camellia sinensis 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 7 to 8 petals.
The seeds of Camellia sinensis and Camellia 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.
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. The young, light green leaves are preferably harvested for tea production; 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 Camellia sinensis var. assamica . It contains about three billion base pairs which was larger than most plants previously sequenced.
Cultivation
Camellia sinensis is mainly cultivated in tropical and subtropical climates, in areas with at least 127 cm (50 inches) 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. Many high quality teas are grown at high elevations, up to 1,500 meters (4,900 feet), as the plants grow more slowly and acquire more flavour.
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. sinensis sinensis) and the large-leaved Assamese plant (C. sinensis assamica), used mainly for black tea.
Chinese teas
The Chinese plant (sometimes called C. sinensis var. sinensis) is a small-leafed bush with multiple stems that reaches a height of some 3 meters. It is native to southeast China. The first tea plant to be discovered, recorded and used to produce tea 3,000 years ago, it yields some of the most popular teas.
C. sinensis var. waldenae was considered a different species, Camellia waldenae by SY Hu, but it was later identified as a variety of C. sinensis. 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 Guangxi province, China.
Indian teas
Three main kinds of tea are produced in India:
- Assam comes from the northeastern section of the country. This heavily forested region is home to much wildlife, including the rhinoceros. Tea from here is rich and full-bodied. It was in Assam that the first tea estate was established, in 1837.
- Darjeeling, from the cool and wet Darjeeling region, tucked in the foothills of the Himalayas. Tea plantations reach 2,200 metres. The tea is delicately flavoured, and considered to be one of the finest teas in the world. The Darjeeling plantations have 3 distinct harvests, termed 'flushes', and the tea produced from each flush has a unique flavour. 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, from a southern region of India almost as high as Darjeeling. Grown at elevations between 1,000 and 2,500 metres, Nilgiri teas are subtle and rather gentle, and are frequently blended with other, more robust teas.
Pests and diseases
Tea leaves are eaten by some herbivores, like the caterpillars of the willow beauty (Peribatodes rhomboidaria), a geometer moth.
Health effects
Although health benefits have been assumed throughout the history of using Camellia sinensis as a common beverage, there is no high-quality evidence that tea confers significant benefits. 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.
Biosynthesis of caffeine
Caffeine is a molecule produced in Camellia sinensis and functions as a secondary metabolite. Caffeine is a purine alkaloid and its biosynthesis occurs in young tea leaves and is regulated by several enzymes. The biosynthetic pathway in C. sinensis differs from other caffeine producing plants such as coffee or guyausa. 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, S-adenosyl-L-methionine synthase encoding for SAM. Younger leaves feature high degrees of TSC1 transcripts, allowing more caffeine to be synthesized during this time. Phosphorylation of xanthosine-5'-monophosphate into xanthosine is the committed step for the xanthosines entering the beginning of the most common pathway. The enzyme S-adenosyl-L-methionine (SAM) helps catalyze xanthosine into 7-methylxanthosine, and the resulting product is converted into 7-methylxanthine through the enzymatic action of 7-methylxanthosine nucleosidase. Caffeine synthase, also referred to as TSC1, catalyzes the conversion of 7-methylxanthine to theobromine, as well as the final conversion of theobromine to caffeine.
See also
Primary green tea catechins
References
External links
- "Camellia sinensis". Integrated Taxonomic Information System.
- Camellia sinensis from Purdue University
- The International Camellia Society
- Plant Cultures: botany and history of the tea plant
- Antibacterial Activity of Green Tea Extracts against Streptococcus anginosus group CI.NII.AC.jp
- Jac.OxfordJournals.org, The effect of a component of tea (Camellia sinensis) on methicillin resistance in Staphylococcus.
- Suns.Ars-Grin.gov, List of Chemicals in Camellia sinensis (Dr. Duke's Databases)
Source of article : Wikipedia
0 Comments