Camellia sinensis: Difference between revisions

The seeds of ''C. sinensis'' and ''[[Camellia oleifera|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.

 

 

[[File:Camellia sinensis MHNT.BOT.2016.12.24.jpg|thumb|''C. sinensis'']]

* [[Assam tea|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 estates of India was established in Assam in 1837. Teas are manufactured in either the ''orthodox'' process or the ''CTC'' process.

* [[Darjeeling tea|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 {{convert|2200|m|ft|abbr=on}}. 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.

[[File:Camellia sinensis-fruto.jpg|thumb|right|200px|Seed-bearing fruit of ''C. sinensis'']]

 

[[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.<ref name="insecticide">{{cite journal | vauthors = Nathanson JA | s2cid = 42711016 | title = Caffeine and related methylxanthines: possible naturally occurring pesticides | journal = Science | volume = 226 | issue = 4671 | pages = 184–7 | date = October 1984 | pmid = 6207592 | doi = 10.1126/science.6207592 | bibcode = 1984Sci...226..184N }}</ref> Caffeine is a purine alkaloid and its biosynthesis occurs in young tea leaves and is regulated by several enzymes.<ref>{{cite journal | vauthors = Li Y, Ogita S, Keya CA, Ashihara H | title = Expression of caffeine biosynthesis genes in tea (Camellia sinensis) | journal = Zeitschrift für Naturforschung C | volume = 63 | issue = 3–4 | pages = 267–70 | date = March 2008 | pmid = 18533472 | doi=10.1515/znc-2008-3-417| doi-access = free }}</ref><ref>{{cite journal | vauthors = Kato M, Mizuno K, Fujimura T, Iwama M, Irie M, Crozier A, Ashihara H | title = Purification and characterization of caffeine synthase from tea leaves | journal = Plant Physiology | volume = 120 | issue = 2 | pages = 579–86 | date = June 1999 | pmid = 10364410 | pmc = 59297 | doi=10.1104/pp.120.2.579}}</ref> The biosynthetic pathway in ''C. sinensis'' differs from other caffeine-producing plants such as [[coffee]] or [[Ilex guayusa|guayusa]]. Analysis of the pathway was carried out by harvesting young leaves and using reverse transcription [[Polymerase chain reaction|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-{{Small|D}}-ribofuranosylxanthine) into [[7-methylxanthosine]], then [[7-methylxanthine]], then [[theobromine]] (3,7-dimethylxanthine), and finally into caffeine (1,3,7-trimethylxanthine).

 

 

== See also ==