ABSTRACT
Today the tea plant known as Camellia sinensis (L) O. Kuntze (named by the famous botanist C. Linne in 1753) is classified into two common species: var. sinensis and var. assamica.
ese above two varieties are currently cultivated in more than 25 countries around the globe (Kitamura, 1950; Weatherstone, 1992). ere are no botanical evidences of the wild-type sources of the aforementioned cultivars. Instead, semi-wild-type cultivars could be found near the areas surrounding Assam and Myanmar. e very first record of the botanical classification was summarized by Linnaeus in 1752, wherein tea cultivars were categorized as Thea bohea and Thea sinensis. Later, on the basis of classification, Thea sinensis became the designation for the small-leaved Chinese variety and Thea assamica the large-leaved Assam plant (Masters, 1844). A compendium of research on the genus of Camellia, dealing with more than 80 tea species for taxonomy, was summarized by Sealy in 1958 (Sealy, 1958, and references therein). In that work, Thea and Camellia were considered to be separate genera and cultivated tea plants included in the genus Thea and the nontea camellias in the genus Camellia. At present, both Thea and Camellia are considered to be synonymous, as the genus Camellia now also relates to the ea family (Sharma and Venkataramani, 1974; Wight, 1962). Table 1.1 shows the different species of tea leaves categorized on the basis of their characteristic
chemical compositions. Growth habitat and leaf features continue to be used to distinguish between C. sinensis and C. assamica. Cultivars of var. sinensis are bush type, a small slow-growing shrub with small, serrate, narrow, dark green leaves. Cultivars of var. assamica are quick growing, tree type, with large, broad, horizontal, light green leaves (Harler, 1956; Sealy, 1958). e var. sinensis can survive in winter as cold as –12°C, whereas those of var. assamica perish at –4°C in a few weeks. erefore, the var. sinensis have been cultivated in the lower temperature regions (Japan, eastern and southern parts of China) and var. assamica in the tropical and subtropical regions (Myanmar, Assam (India), and Yunnan (China)). A universally acceptable set of criteria for differentiating the three modern tea cultivars are provided by floral morphology (via disposition of the stylar arm), a variation in the number of styles and the degree of their fusion, and a globular or pubescent ovary is effectively considered. As an example, the styles are free for most of their length in C. sinensis,
Different Tea Species Distributed in Relevant Category on the Basis of Their Characteristic Chemical Compositions
fused for most of their length in C. assamica, and remain free for nearly half their length in C. assamica ssp. lasiocalyx. Additionally, C. irrawadiensis and C. taliensis cultivars are known for their potential contribution to the tea gene pool, but are not grown commercially, as they only produce teas considered low quality . A number of other Camellia species are historically grown as ornamental plants, wherein C. japonica, C. reticulata, and C. sasanqua are still popular worldwide (Gao et al., 2005). In addition, seeds from species of C. japonica and C. oleifera have been widely used for oil extraction in Japan and China, respectively (Sealy, 1958). On the other hand, C. japonica and C. reticulate (both camellias), and C. sasanqua (paracamellia), are known to contribute to understanding the phylogenesis of Camellia species. Since the tea plant is easily cross-pollinated by fertilization of transferring pollens, the hybrid clines of C. sasanqua × C. sinensis, C. sinensis × C. japonica, and C. japonica × C. kissi are also known, since hybridization takes place promptly (Visser, 1969) (Table 1.1). e classification has been continued with a number of revisions after careful review and reexamination of their physical, chemical, and genetic properties. In the 1980s, after examining 280 Camellia species, Chang (1981) classified them into 4 subgenera and 14 sections . Later, Ming (2000) divided them into 2 subgenera and 14 sections on the basis of structural framework proposed by Sealy (1958). e classification is still continuing using modern techniques of genetic isolations and has been further grouped (Vijayan et al., 2009; Wachira et al., 1997). When the classification based on the three major components of tea, polyphenols, theanine, and caffeine, which are relevant for health benefits of tea, was reviewed, all three components were present in varied amounts in the species of subgenera Thea, mainly in C. sinensis, and its wild relatives C. taliensis and C. irrawadinesis, or among the hydrides of C. sinensis only. On the other hand, the species belonging to subgenera Camellia do not contain even trace amounts of theanine and caffeine (Table 1.1), the major contributors for the pleasure of drinking tea. It could be postulated that the absence of these compounds in the species of subgenera of Camellia could have led them to establish as a nontea plant species.
