2. LITERATURE REVIEW 2.1. Taxonomic treatments Family Polygonaceae was established and published by A. L. Jussieu (1789) in Genera Plantarum. Around 1200 species representing 48 genera are geographically distributed from the tropics to the arctic, although most species are concentrated in the northern temperate region (Heywood 1978; Freeman and Reveal 2005; Sanchez and Kron 2008). Polygonaceae Jussieu commonly known as the Buckwheat, Smartweed or Knotweed family is one of the complex group among the class Magnoliopsida regarding its identification. The family name was derived from Greek word “Polygonon”, “Polys” meaning many and “gonon” meaning Knee referring to the prominent nodes of many species (Komarov 1970). Bentham and Hooker (1880) placed Polygonaceae Jussieu in their classification as follows: Kingdom: Phanerogamia Class: Dicotyledonae Sub class: Monochlamydae Series: Curvembryae Family: Polygonaceae Cronquist (1981) placed Polygonaceae in his classification as follows: Division: Magnoliophyta Class: Magnoliopsida Sub class: Caryophyllidae Order: Polygonales Family: Polygonaceae 11 Takhtajan (1997) placed Polygonaceae in his classification as follows: Division: Magnoliophyta Class: Magnoliopsida Subclass: Caryophyllidae Order: Polygonales Family: Polygonaceae APG IV (2016) placed Polygonaceae in the classification as follows Kingdom: Plantae Clade: Core Eudicots Clade: Superasterids Superorder: Asterids Order: Caryophyllales Family: Polygonaceae Type genus: Polygonum Linnaeus 2.2. General characteristics Polygonaceae is a very complex family due it’s most diverse and peculiar morphological features. Members of the Polygonaceae are showing variable habit range from annual or perennial herbs, shrubs to lianas and some trees. The most distinctive feature of the family is the presence of membranous or hyaline sheath uniting the stipules (except Antigonon Endl., Eriogonum Michx. etc). Leaves are simple usually alternate but in some cases they can be opposite (Pterostegia Fisch. and C. A. Mey., some species of Polygonum L. and Eriogonum Michx.). Nectary discs are usually present and the nodes are typically swollen (Hutchinson and Dalziel 1954). The flowers are usually perfect and actinomorphic with a perianth of three to six sepals, often in two whorls of three or one whorl of five. After flowering sometimes the sepals become enlarged around the developing fruit. Flowers lack corolla and in some taxa the sepals are petal-like and colorful. Androecium is composed of three to eight stamens that are normally free or united at base (Jones and Luchsinger 1979). Three united carpels of ovary forms a single locule, which in turn produces only one ovule. Superior ovary with basal or free central placentation 12 is the unique feature of the family. Gynoecium terminates 1–3 styles, each of which ends in a single stigma. Ovule is mostly orthotropus, fruit is trigonous nut and seeds have copious endosperm (Cronquist 1981). Seeds are erect, testa membranous, albumen floury or horny. Embryo is various, radicle superior (Maiti and Sikdar 1985). 2.3. Economic importance Most of the species of the family Polygonaceae were growing in waste areas as weeds. But, few genera of Polygonaceae were reported as economically important for their widespread uses (Steward 1930). However, Cardoso et al. (2006) studied and analyzed the medicinal and chemical properties from different species Polygonaceae. The complex genus Polygonum L. has some economic importance. P. aviculare L. is an accepted widely in international pharmaceutical market, sold in German drug stores as Homeriana Tea; it contains 2–2.5% sugar, traces of essential oil, tannin, resin and wax. Its seeds are cathartic and emetic (Bamber 1916). It is also popular as good fodder plant and its roots yield a blue dye (Komarov 1970). It is a bad weed, resistant to herbicide (Mabberley 1987). It is used as an astringent, tonic, antipyretic, diuretic and extract is given against dysentery. P. plebium R. Br. was reported as medicine used to cure pneumonia (Agarwal 1997). The leaves of P. arenastrum Boreau. contains tannins and is used as medicine (Zohary 1966). Its aerial parts has haemostatic action (Joachimovits 1959) used as antiseptic (Gupta 1995) and internally as antihaemorrhoidal, astringent and antirheumatic (Mors et al. 2000). The plant is also famous for its antifertility properties (Garg et al. 1978; Sarma and Mahanta 2000). Infusions and decoctions are made from P. lapathifolium L. and used as cathartic and emetic drugs. The infusion of P. persicaria L. leaves is used to relieve stomach pains and its decoction is used in the treatment of rheumatism (Moerman 1998). Fleshy roots of P. viviparum L. are cooked because of its almond flavour and also used as a substitute for nuts and raisins (Szczawinski and Hardy 1972). Some species of Persicaria are economically important worldwide such as P. capitata (Buch-Ham. ex D. Don) H. Gross and P. orientalis (L.) Spach are used as ornamental plants in China (Lorenzi and Souza 1999). Root of P. chinensis (L.) H. Gross (Mountain knotweed or Chinese knotweed) is used for the treatment of fluxes, 13 antihelminthic and neutralizes scorpion poisoning. Extract of P. minor (Huds.) Opiz is mixed with rice powder and used on affected area to cure sprains and body aches. The plant is also used as an antidote for dyspepsia in children (Wiart 2006). Watery sap obtained from the roots of P. barbata (L.) H. Hara is used as an antiseptic (Watt and Breyer-Brandwijk 1962). The rhizome of Bistorta amplexicaulis (D. Don) Green is used for making tea and decoction (Qaiser 2001). Fagopyrum Mill. (Buckwheat) is reported to be economically important genus (Campbell 1995). In China, F. dibotrys (D. Don) Hara is used for the treatment of lung diseases, including lung tumor (Liu et al., 1981). In India, its seeds are used for the treatment of colic, choleraic diarrhoea and abdominal blockage troubles (Samaiya and Saxena 1989). Its leaves are used as vegetable and crushed grains given against the stomach disorders (Qaiser 2001). Polyphenols like rutin and quercetin have been isolated from F. esculentum Moench. has anti-inflammatory and anticarcinogenic properties (Oomah and Mazza 1996). Leaves are edible and nectar famous for the production of honey that is used for the treatment of various blood diseases (Campbell 1997; Erlund et al. 2000; Qaiser 2001). In China, Japan, Korea it is use as non poaceous alternative human crop, famous for its nutritious qualities (Wijngaard and Arendt 2006). F. tataricum (L.) Gaertn. (Tatary buckwheat) used for the treatment of bleeding gums and the people who used tatary buckwheat flour for brushing their teeth and gargling showed 62% recovery in their gum diseases (Song and Zhou 1992). It is an important crop in Himalayan hills and mountain regions of southern areas of China (Tsuji and Ohnishi 2001). High proportion of anthraquinones is present in the genus Rumex L. and the roots of R. dentatus L. are used as an astringent and for dyeing purposes because of high percentage of tannin (Hongo 1986; Watt and Breyer-Brandwijk 1962). The leafy juice of R. vesicarius L. produces cooling effect in snake bite (Qaiser 2001). 2.4. Genus under Polygonaceae Different authors documented 30 to 59 genera under the family Polygonaceae. The major genera are Eriogonum (240 species), Rumex (200 species), Coccoloba (120 species), Persicaria (100 species) and Calligonum (80 species) (Freeman and 14 Reveal 2005). According to Cronquist (1981) the family is represented by 30 genera, where as Freeman and Reveal (2005) reported 48 genera for Polygonaceae. Brandbyge (1993) distinguished the Polygonaceae family with 43 genera (Table 1) while according to Plantlist (www.plantlist.org) the family comprises 59 genera. Table 1: Genera under the family Polygonceae (Brandbyge, 1993) Sl. Genera Sl. Genera No. No. 1. Antigonon Endl. 23. Millspaughia Robins. 2. Aristocapsa Reveal and Hardham 24. Mucronea Benth. 3. Atraphaxis L. 25. Muehlenbeckia Meisn. 4. Brunnichia Banks ex Gaertn. 26. Neomillspaughia S. F. Blake 5. Calligonum L. 27. Oxygonum Burch. ex Campd. 6. Centrostegia A. Gray ex Benth. 28. Oxyria Hill 7. Chorizanthe R. Br. ex Benth. 29. Oxytheca Nutt. 8. Coccoloba P. Browne 30. Persicaria (L.) Mill. 9. Dedeckera Reveal and J. T. Howell 31. Podopterus Humb. and Bonpl. 10. Dodecahema Reveal and Hardham 32. Polygonella Michx. 11. Emex Neck. ex Campd. 33. Polygonum L. 12. Eriogonum Michx. 34. Pteropyrum Jaub. and Spach 13. Fagopyrum Mill. 35. Pterostegia Fisch. and C. A. Mey. 14. Fallopia L. 36. Reynoutria Houtt. 15. Gilmania Coville 37. Rheum L. 16. Goodmania Reveal and Ertter 38. Rumex L. 17. Gymnopodium Rolfe 39. Ruprechtia C. A. Mey. 18. Harfordia Greene and Parry 40. Stenogonum Nutt. 19. Hollisteria S. Watson 41. Symmeria Benth. 20. Koenigia L. 42. Systenotheca Reveal and Hardham 21. Lastarriaea Remy 43. Triplaris Loefl. ex L. 22. Leptogonum Benth. 15 2.5. Geographical distribution The family containing approximately 59 genera and about 1384 species (www.theplantlist.org) geographically distributed from the tropics to arctic, although most species are concentrated in the northern temperate region (Heywood 1978). Many of the members of this family are confined to Himalayan regions of which West Bengal occupies the prominent position. India is represented by 121 species and 29 varieties belonging to 12 genera of Polygonaceae (Srivastava 2014). Most of the species of Polygonum sensu lato were distributed primarily in the Himalayan region, with a few species in tropical regions (Fig 1). Fig. 1: Major distribution areas of Polygonum sensu lato in India (Choudhary et al. 2012) 16 The following table shows the distribution of some species of Polygonaceae in West Bengal, India and Worldwide. Table 2: Distribution ranges of some species of Polygonaceae grow in Himalayas (Maiti & Sikder 1985; Rai 2007; Lepcha 2011; Srivastava 2014) DISTRIBUTION SL NO. TAXA West Bengal India Global Aconogonon molle (D. 01. Darjeeling, Kalimpong Sikkim (Kupup, Jelepa 3050-4200), Meghalaya Nepal, Bhutan, Indo-China, Malaysia Don) H.Hara Bistorta emodii (Meisn.) 02. Darjeeling Sikkim (Rachela peak) to Simla W. China H.Hara Bistorta macrophylla (D. Sikkim (Zuluk, Kyongnosla), Himachal Pradesh, 03.