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|Vol. 13(3), pp. 8-16||The McAllen International Orchid Society Journal||March 2012|
Effective Publication Date : 1-Mar-2012
1 Daisa Bordoloi Nagar, Talap, Tinsukia - 786156, Assam, India
2 Nature's Foster, P. Box 41, Shastri Road, P.O. Bongaigaon, 783380, Assam, India
3 St. Joseph's College, P.O. North Point - 734104, District Darjeeling, W. B., India
* Corresponding author E-mail: email@example.com
(All figures are credited to first author.)
Orchid species viz. Dendrobium fugax, Dienia ophrydis, Eulophia bicallosa, Gastrochilus inconspicuus, Phaius mishmensis, Rhynchostylis retusa and Zeuxine strateumatica have been shown intraspecific colour variations in the natural populations of Orchid species of Assam. Colour variation was observed in floral parts viz., sepals, petals and lip. In this paper all the species are enumerated with a brief description of each.
Orchidaceae, colour variation, environment, Assam.
Many flowering plants saw their floral variation in colour for attracting different pollinators and this variation particularly well represented in the orchid family. Approximately one-third of all of the 30,000 species known to science bear only rewardless flowers (Dafni, 1984; Nilsson, 1992; Cozzolino and Widmer, 2005; Gogoi, 2005; Gogoi et al. 2009; Schiestl, 2005; Tremblay et al. 2005; Bhagabati et al. 2006; Jersakova et al. 2006, 2009).
Orchidaceae, one of the largest families of flowering plants is comprised of a unique assemblage of highly advanced monocotyledonous plants. They exhibit amazing diversity in terms of their size, shape, structure, number, density, colour and fragrance of flower and many species show intraspecific variation in floral colour. However, the minute colour variation is not a valid criteria to place it into a new species or variety. Thus, the variation observed may be due to environmental influence and natural selection.
Assam is the second largest state of North-East India and is a rich store house of Indian orchid species. The total number of orchid species may be around 193 in 71 genera of which 27 are endemics (Rao 1995, Hegde 2000). It is estimated that at about 25,000-35,000 species with 800-1,000 genera are distributed throughout the world. About 1300 species with 140 genera of Orchid species are found in India with the temperate Himalayas as their natural home (Yonzone and Kamran, 2008). In Assam orchid species viz. Dendrobium fugax, Dienia ophrydis, Eulophia bicallosa, Gastrochilus inconspicuus, Phaius mishmensis, Rhynchostylis retusa and Zeuxine strateumatica have been shown to exhibit intraspecific colour variation in their populations. In the present investigation, the intraspecific colour variations observed in the natural population of these species has been studied with attention to habitat, phenology, altitudinal range and current status.
During field survey, in the year of 2006 to 2011 in different parts of Assam some variation in colour of floral parts of four orchid species were observed. The specimens were collected without uprooting and disturbing the plants in the nature. Some unusual floral colour was observed. Further, a survey was conducted to confirm the variation in the same locality in same season the following year.
The specimens were studied in the laboratory for identification and to study why there is colour variation. The work was done following the classification given by Lindley (1852-1855); and (1830-1840); King and Pantling (1898); Duthie (1906); Gamble (1982); Pangtey et al. (1991); Chowdhery (1998); Deorani and Naithani (1995); Deva and Nathani (1968); Hooker J.D. (1890); Pradhan (1976); Pradhan (1979); Seidenfaden (1962); Pearce and Cribb (2002); Lucksom (2007).
Voucher specimens have been deposited in the Herbarium, Department of Botany, Gauhati University. Recent nomenclature has been checked with available literature.
Fig. 1. Dendrobium fugax.
Fig. 2. Dendrobium fugax.
1. Dendrobium fugax Rchb. f., Gard. Chron. 1257. 1871. (Fig. 1) (Fig. 2)
Synonym: Flickingeria fugax (Rchb. f.) Seidenf. in Dansk Bot. Ark. 34: 46. (1980)
Homtypic Synonyms: Dendrobium fugax Rchb. f. Gard. Chron. 1871: 1257 (1871). Callista fugax (Rchb. f.) Kuntze, Revis. Gen. Pl. 2: 654 (1891). Basionym/Replaced Synonym.
Flowers: White, 1 or 2, arising at the base of leaf, 3-3.5 cm across, fugacious; dorsal sepal ligulate; petals much narrower than the sepals; lip purple marked or white, 3 lobed, oblong, dilated from a cuneate base; side lobes truncate at apex; mid lobe clawed, abruptly hastate-fan shaped; keels 2, membranous, crenulate and lobulate; column very short.
Flowering: March - October.
Habitat: Epiphyte in humid evergreen forest, mixed deciduous forest.
Fig. 3. Dienia ophrydis.
Fig. 4. Dienia ophrydis.
2. Dienia ophrydis (J. Konig) Seidenfaden, Contr. Orchid Fl. Thailand 13: 18. 1997. (Fig. 3) (Fig. 4)
Synonyms: Malaxis latifolia Blume, Bijdr.: 393 (1825), nom. Illeg. Malaxis latifolia J.E. Smith in Pradhan, Indian Orchid-II, 208, 1979; Kumar et. Monilal, Cat. Ind. Orch., 79, 1994; Chowdhery, Orch. Fl. Arunachal Prad., 504, 1998. Malaxis latifolia Sm. In A. Rees, Cycl. 22: 3 (1812). Malaxis latifolia var. nana S.S.Ying, mem. Coll. Agric. Natl. Taiwan Univ 25: 101 (1985).
Homtypic Synonyms: Microstylis latifolia (Sm.) J.J.Sm. Orch. Java: 248 (1905). Gastroglottis latifolia (Sm.) Szlach., Fragm. Florist. Geobot., Suppl. 3:123 (1995). Dienia latifolia (SM.) M.A.Clem. & D.L.Jones, Lasianthera 1:41 (1996). Corymborkis latifolia (Sm.) M.R.Almeida, Fl. Maharastra 5A: 30 (2009).
Inflorescence: Nearly as long as leaf; rachis many flowered; floral bracts small; flowers purple or greenish yellow; petals narrowly linear, 8 × 1mm; lip subobovate-oblong, 10 × 3 mm, deeply bilobed, with a bilobed basal callus; apical lobes divergent, suboblong, 4-5 × 2.5-3 mm, apex irregularly toothed; column 3-3.5 mm, upper part with narrow wings.
Flowering: May - June.
Habitat: Terrestrial in open humid evergreen forest.
Fig. 5. Eulophia bicallosa.
Fig. 6. Eulophia bicallosa.
3. Eulophia bicallosa (D.Don) P.F.Hunt & Summerh., Kew Bull. 20: 60 (1966). (Fig. 5) (Fig. 6)
Flowers: Medium-sized, 2.5-3 cm across; sepals and petals yellowish green, lip white or sepals pale green, with 5 purple veins; petals pale white with purplish vain, lip white with dark purple venation; dorsal sepal lanceolate, 13 × 3 mm, apex acute; lateral sepals lanceolate, 13 × 3- 5 mm, adnate at base to column foot, apex acute; petals lanceolate to narrowly elliptic, 13 × 7-8 mm, base contracted, apex acute; lip subovate, 15 mm, spurred at base, 3-lobed; lateral lobes erect, triangular, oblique; mid-lobe recurved, broadly ovate, clawed at base, apex retuse; disk with 3 purplish red ridges; spur saccate, 4 mm, apex obtuse; column 6 mm, slender, with a distinct column foot 3 mm.
Habitat: Terrestrial, growing in grass land.
Fig. 7. Gastrochilus inconspicuus.
Fig. 8. Gastrochilus inconspicuus.
4. Gastrochilus inconspicuus (Hook. f.) Kuntze, Revis. Gen. Pl. 2: 661 (1891); Pradhan, Indian Orchid-II, 556, 1979; Kumar et. Monilal, Cat. Ind. Orch., 75, 1994; Chowdhery, Orch. Fl. Arunachal Prad., 413, 1998; Chowdhery & Pal, Orch. Arunachal Prad., 89, 1997. (Fig. 7) (Fig. 8)
Flowers: In extra axillary, solitary, 3-5 flowered spikes, 0.5cm across, white with column purple or yellowish-green with yellowish-green column; sepals ovate- lanceolate; petals oblong; lip saccate at base; mid lobe subreniform, notched at apex, 5-6 vertical lines on its upper surface; column stout.
Flowering: June - July.
Habitat: Epiphyte in humid evergreen forest, mixed deciduous forest.
Fig. 9. Phaius mishmensis.
Fig. 10. Phaius mishmensis.
Fig. 11. Phaius mishmensis.
5. Phaius mishmensis (Lindley & Paxton) Rchb. f. in Bonplandia 5: 43. (1857); Hook. f., Fl. Brit. India 5: 817. 1890. (Fig. 9) (Fig. 10) (Fig. 11)
Flowers: 4-5 cm across; sepals and petals pale pink to dark red or pale yellow or white; sepals similar, elliptic, 2.5-3.5 × 0.5-1.2 cm, glabrous, apex subacute; petals oblanceolate, 2-3.5 × 0.4-0.7 cm, apex obtuse; lip white to pink, densely reddish brown spotted or white, obovate-triangular, 2-3.5 × 1.5-2.5 cm, 3-lobed; lateral lobes ovate, margins flat or slightly undulate, apex obtuse or rounded; mid-lobe subsquare or broadly obovate, margin undulate, apex emarginate to retuse; disk with 3 or 4 densely hirsute-pubescent ridges extending to mid-lobe; spur slightly curved, yellow-green, narrowly cylindrical, 1-1.6 × 0.2 cm, apex obtuse; column yellow or whitish, 2.2 cm, densely villous ventrally.
Flowering: November - January.
Habitat: Terrestrial, on the bank of a small stream in dense humid evergreen forest.
Fig. 12. Rhynchostylis retusa.
Fig. 13. Rhynchostylis retusa.
6. Rhynchostylis retusa (Lindley) Blume, Bijdr. 286, t. 49. 1825; Hook. f., Fl. Brit. India 6: 32. 1890. (Fig. 12) (Fig. 13)
Synonym: Rhynchostylis albiflora Borua & Bora in Jour. Econ. Taxon. Bot., 26(1), 2002.
Homtypic Synonym: Rhynchostylis retusa f. albiflora (I.Barua & Bora) Christenson, J. Orchideenfr. 12: 344. 2005.
Flowers: White or white with purple spotted, 1.7-2.3 cm across, sepals and petals white and spotted with pink or pale purple or white and without pink spot, lip purplish white or pink with white apex, spur white; pedicel and ovary 7-10 mm; dorsal sepal elliptic, 7-11 × 4.2-5 mm, obtuse; lateral sepals obliquely oblong, 7-11 × 4.5-5.5 mm, base adnate to column foot, apex obtuse; Petals narrowly oblong, 7-7.5 × 2.5-3 mm, obtuse; lip often conduplicate, oblong-spatulate, 8-10 × 5-6 mm, rounded, apiculate, or slightly retuse, spurred; spur laterally compressed, 6-8 mm, rounded; column ca. 4 mm, foot 2 mm.
Flowering: May - June.
Habitat: Epiphyte in the evergreen tropical forest, mixed deciduous forest and also on solitary roadside trees.
Fig. 14. Zeuxine strateumatica.
Fig. 15. Zeuxine strateumatica.
7. Zeuxine strateumatica (L.) Schlechter in Engler, Bot. Jahrb. 45: 394 (1911). Chowdhery, Orch. Fl. Arunachal Prad. 695. 1998. (Fig. 14) (Fig. 15)
Synonyms: Zeuxine strateumatica var. laxiflora I.Barua, Orchid Fl. Kamrup Distr. Assam: 52 (2001). Zeuxine strateumatica f. rupicola (Fukuy.) T.Hashim., Ann. Tsukuba Bot. Gard. 5: 27 (1986). Zeuxine strateumatica var. rupicola (Fukuy.) S.S.Ying. Col. Ill. Indig. Orch. Taiwan 1(2): 512 (1977).
Inflorescence: 2-30 cm, glabrous, with a few to more than 20 densely arranged flowers; floral bracts reddish brown or greenish white, ovate-lanceolate, 8-12 mm, acuminate; flowers white or puplish white, small; sepals glabrous, dorsal sepal narrowly ovate-oblong, concave, 4-6 × 2-3 mm, 1-veined, apex obtuse, lateral sepals obliquely oblong, 4-5.5 × 1.5-2.5 mm, 1-veined, apex acute or obtuse; petals subovate to obovate, oblique, 4-5.5 × 1.5-1.8 mm, glabrous, 1-veined, apex obtuse; lip pale yellow to yellow, cymbiform, 4-5 mm, 3- partite; hypochile concave-saccate, containing 2 subtriangular, lamellate calli; mesochile ca. 1 mm, exterior surfaces minutely papillate toward apex, margin denticulate, involute; epichile transversely elliptic-oblong, 1.4-1.8 × 2-2.5 mm, minutely papillate, apex with a small mucro to slightly emarginated; column ca. 1.5 mm.
Flowering: January - March.
Habitat: Terrestrial, growing in grass land.
During the present investigation colour variation was observed in 7 orchid species; 3 species epiphytic and 4 species terrestrial.
In Dendrobium fugax Rchb. f. colour variation was found on the lip. The variation can be recognized with white colour lip. Both variations are found in Lakhapani Reserve forest, Tinsukia, Assam.
In Dienia ophrydis (J. Konig) Seidenfaden two colour variations are found. One with purple flowers and another with greenish yellow flowers. Both variations are found in Hawang in Karbi- Anglong, Assam.
In Eulophia bicallosa (D.Don) P.F.Hunt & Summerh. two colour variations are found; sepals and petals yellowish green, white liped flowers or sepals pale green, with 5 purple veins; petals pale white with purplish vain, lip white with dark purple venations flowers. Variations are observed in Manas National Park, Assam.
In Gastrochilus inconspicuus (Hook. f.) Kuntze two colour variations are found; white with column purple flowers or yellowish-green with yellowish-green column flowers. Variations are observed in Manas National Park and Karbi- Anglong, Assam
In Phaius mishmensis Rchb. f. three different colour variations are found, sepals and petals pale pink to dark red with white to pink with densely reddish brown spotted lipped flower and sepals and petals pale yellow with white to pink with densely reddish brown spotted lipped flower and white flower. All variations are observed in Joypur Reserve forest, Dibrugarh, Assam.
In Rhynchostylis retusa (Lindley) Blume two different colour variations are found; white or white with purple spotted flower. The white flowered R. retusa described as Rhynchostylis albiflora Borua & Bora (Borua & Bora, 2002). The variations are observed in Tinsukia, Sibsagar and Jorhat district of Assam.
In Zeuxine strateumatica (L.) Schlechter two colour variations are found; floral bracts reddish brown, sepals and petals pale purple with yellow lipped flower and floral bracts greenish white, sepals and petals white with yellow lipped flower. The variations are observed in Dibru- Saikhowa National Park, Tinsukia, Assam.
These intraspecific variations can be easily recognized with the described flower colour. Drastic colour variation found on mainly sepals, petals and lip. It is confirmed that variation is on colour of floral parts but in plant taxonomical science, minute color variation is insufficient criteria to place or categories it as a new species, variety or forma (Bhujel, 1996). However, some biologists consider it as a trend and distinguish such plants as a new species, variety, or forma. Therefore, because such present variations are absolutely based on colour of floral parts especially sepals, petals and lip and it is concluded these represent neither a new species nor a variety or forma respectively, but intraspecific variations. Such variations may have occurred due to long term environmental influences coupled with natural selection pressures for survival within changed environmental conditions.
The authors are grateful to Dr. Kashmira Kakoti, Dr. A. Cristy Williums, Deputy Commissioner-Dibrugarh and Department of forest, Assam for constant supervision and valuable suggestions during the course of present studies.
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