Theaceae

Theaceae
Tea Camellia sinensis
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Asterids
Order:	Ericales
Family:	Theaceae D.Don
Genera
See text.
Synonyms
Camelliaceae

Theaceae /iːˈs/ is a family of flowering plants, composed of shrubs and trees, including the camellias. It can be described as having from seven to 40 genera, depending on the source and the method of circumscription used. The family Ternstroemiaceae has been included within Theaceae; however, the APG III system of 2009 places it instead in Pentaphylacaceae.

Family characteristics

Plants in this family are characterized by simple leaves that are alternate spiral to distichial, serrated, and usually glossy. Most of the genera have evergreen foliage, but Stewartia and Franklinia are deciduous. The toothed margins are generally associated with a characteristic Theoid leaf tooth, which is crowned by a glandular, deciduous tip. The flowers in this family are usually pink or white and large and showy, often with a strong scent. The calyx consists of five or more sepals, which are often persistent in the fruiting stage, and the corolla is five-merous, rarely numerous. Plants in Theaceae are multistaminate, usually with 20-100+ stamen either free or adnate to the base of the corolla, and are also distinctive because of the presence of pseudopollen. The pseudopollen is produced from connective cells, and has either rib-like or circular thickenings. The ovary is often hairy and narrows gradually into the style, which may be branched or cleft. The carpels are typically opposite from the petals, or the sepals in the case of Camellia. The fruits are loculicidal capsules, indehiscent baccate fruits or sometimes pomes. The seeds are few and sometimes winged, or in some generas covered by fleshy tissue or unwinged and nude.

Genera

As of March 2017, the Angiosperm Phylogeny Website accepts the following genera:

• Apterosperma Hung T. Chang
• Camellia L., including Piquetia (Pierre) H.Hallier, Thea L., Yunnanea Hu
• Dankia
• Franklinia Marshall
• Gordonia Ellis, including Laplacea
• Polyspora G.Don
• Pyrenaria Blume, including Dubardella H.J.Lam, Glyptocarpa Hu, Parapyrenaria H.T.Chang, Sinopyrenaria Hu, Tutcheria Dunn
• Schima Blume
• Stewartia L., including Hartia Dunn

The fossil Pentapetalum trifasciculandricus, about 91 million years old, may belong to the Theaceae or the Pentaphylacaceae.

Chemistry

There is distinctive chemistry within the Theaceae family. Sometimes, single crystals of calcium oxalate are present in Theaceous plants. Ellagic acid and common polyphenols including flavonols, flavones and proanthocyanins are widely distributed throughout the family. Gallic acid and catechins only occur in Camellia sect. Thea (C. sinensis, C. taliensis and C. irrawadiensis.) Caffeine and its precursors theobromine and theophylline are only found in sect. Thea and are not found in other species of Camellia or other Theaceae. Caffeine content in the tea bush makes up 2.5-4% of the leaf's dry weight, and this high content of catechins and caffeine in the tea bush is the result of selection by man for these characters. Triterpenes and their glycosides (saponins) are found widely throughout the family in the seeds, leaves, wood and bark. Plants in this family are also known to accumulate aluminum and fluoride.

Distribution

Members of the family are found in south-east Asia and Malesia, tropical South America and the south-east United States. Three genera (Franklinia, Gordonia and Stewartia) have species native to the south-east United States, with Franklinia being endemic there, and under some interpretations, also Gordonia with the Asian species formerly included in that genus being transferred to Polyspora.

Economic importance

The best known genus is Camellia, which includes the plant whose leaves are used to produce tea (Camellia sinensis). In parts of Asia, other species are used as a beverage, including C. taliensis, C. grandibractiata, C. kwangsiensis, C. gymnogyna, C. crassicolumna, C. tachangensis, C. ptilophylla, and C. irrawadiensis. Several species are grown widely as ornamentals for their flowers and handsome foliage.