THE GENUS DENDROBIUM IN DIBRU-SAIKHOWA NATIONAL PARK AND BIOSPHERE RESERVE Khyanjeet Gogoi Bordoloi Nagar, Talap, Tinsukia-786156, Assam, India Abstract Thirty five of epiphytic orchids including the floriculturally significant Dendrobium moschatum, D. fimbriatum, D. nobile, D. transparens, D. lituiflorum, D. aphyllum, D. aduncum were recorded from Dibru-Saikhowa National Park and Biosphere Reserve in an intensive survey during 1996-2002. The dendrobes are described, highlighting their important features for easy identification. Introduction DENDROBIUM REPRESENTS a large group of morphologically diverse and epiphytic orchids, known for beautiful and long-lasting flowers of various colours, hues and shades. It is the second largest genus of the family Orchidaceae, comprises more than 1,000 species, and is widely distributed in Sri Lanka, India, China, Japan, Malaysia, Australia and New Zealand. In India, it is represented by 102 species, 20 of which grow in Assam (Barua 2001). The genus is popular with both the amateur and professional growers having contributed immensely to commercial floriculture. The Dibru-Saikhowa National Park and Biosphere Reserve is a natural home to a variety of epiphytic orchids. While a detailed inventory has remained elusive, progressive decline in the forest cover, due to anthropogenic pressures, has detrimentally affected the size and distribution frequency of orchid populations. Fig. 1. Map of India showing location of Dibru-Saikhowa National Park and Biosphere Reserve in Assam. Accepted: April 10, 2005
Several species are threatened of survival. The writer repeatedly surveyed the Park with a view to assessing the current status of orchid diversity. As many as 35 species including 7 that belong to the genus Dendrobium have so far been collected. This paper describes the salient taxonomic features of the dendrobiums. Study Area Materials and Methods The Dibru-Saikhowa Park and Biosphere reserve, the richest in Upper Assam and one of the nineteen biodiversity hot spot of the world, is located along the northern bank of river Brahmaputra. Originally spread over an area of 640 Km², it was declared that Wild Life Sanctuary in 1986, and subsequently as a National Park 1999 with a core area of 340 Km² and a large surrounding buffer zone under Tinsukia and Dibrugarh district. It extends between 27 o 35-27 o 50 N and 95 o 10-95 o 15 E in the flood plains of Brahmaputra and Lohit river at an attitude of 118 m (Sarmah, 1998; Mahanta, 2002). The climate here is subtropical moist with an average annual rainfall between 3800 and 2300 mm, temperature between 36 o C and 6 o C and relative humidity between 86 and 64 (Sarmah, 1998). The forest include semi-wet evergreen, tropical moist deciduous, littoral and swamp types with patches of bamboo and cane brakes etc. Area wise the National Park comprises 35.8% of moist mixed forests, 9.5% of degraded forests, 21.3% of savanna grassland, about 1.8% cultivated land, 4.1% of Barren land, 10.3% of free water, and 17.1% sandy cover (Mahanta, 2002). Live collections of orchids, at different stages of development, were made at monthly intervals during 1997-2003, and maintained at the Department of Botany, Sibsagar College for ready availability of plant material during taxonomic evaluation. Identifications were done using standard orchid manuals and other regional publications (Banerji, 1978; Barua, 2001; Bruhl, 1926; Gamble, 1928; Hegde,1984; Hooker, 1890; Novak, 1965; Pradhan, 1979). Voucher specimens have been deposited in the Herbarium, Department of Botany, Sibsagar College, Joysagar (Assam). Species Description Dendrobium moschatum (Buch-Hum) Sw. in Hegde, Orch. Arunachal Prad. 64, 1984; Pradhan, Ind. Orch.2, 308, 1979; Roy, Orch. Ind., 59, 1979; Banerji, Orch. Nepal, 63, 1978; Bruhl, Orch. Sikkim, 64, 1926; Kumar et. Monilal, Cat. Ind. Orch., 71, 1994; Barua, Orch. Fl. Kamrup Dist., 159, 2001. Dendrobium calceolaria Caruy ex Hook; Fl. Brit. Ind. 5, 744, 1890. Plants with pseudobulbs. Stems 1-2 meter long, terete striate, pointed towards the apex, erect or sub erect. Leaves several, alternate, acute or faintly notched, ovate to lanceolate ovate, 10-15 x 3.5 cm. Inflorescence arising from apical region of the leafless or leafy stem; Fig. 2. Dendrobium moschatum (Buch.-Hum.) Sw. 10-30 cm Long. Flowers 4-15, 5-7 cm across, showy, orange yellow. Sepals broadly ovate, obtuse, dorsal sepals 4 x 1.8 cm, lateral sepals 4 x 1.7 cm. Petals 4.3 x 3 cm, broadly ovate, rounded, sessile or subsessile or clowed. Lip hairy, shorter than petals, forming a
Orch. Ind., 58, 1979; Kumar et. Monilal, Cat. Ind. Orch., 70, 1994; Barua,Orch. Fl. Kamrup Dist., 163, 2001. Pseudobulbs 75-150 cm. long, erect or sub-erect; tapering towards the apex. Leaves several, lanceolate acuminate, gradually tapering to an acute apex,10-15 x 1.5-2.8 cm. Inflorescence pendulous, 8-12 flowered raceme, born laterally on leafy or leafless stem, 15-20 cm long. Flowers 4-5 cm across, bright yellow, sweet scented. Sepals broadly oblong, rounded, entire, 2.5 x 1.3 cm. Petals broader, suborbicular, 2.5 x 1.7 cm. Lip orbicular, fimbriate, pubescent, 3 x 2.5 cm, bright yellow with reddish streak at base and without a purplish-brown blotch. Column foot 0.9 cm. long. (Fig. 4, 5) Flowering: April May Fig. 3. Dendrobium moschatum (Buch.-Hum.) Sw.: A, Habit; B, Floral bract; C, Perigone; D, Lip; E, Column; F, Fruit. hemispherical or pear-shaped open mouthed pouch with the upturned margins, two darkmaroon blotches present inside the base. Column yellow with purple tinge at top. Ovary upto 5 cm. Fruit 7-9 x 1.5 cm. (Figs. 2, 3) Flowering: May-June Occurrence: Common, grows at a height of 4-10 m on trees like Salix tetrasperma, Bischofia javonica, Premna bengalansis etc. Dendrobium fimbriautm Hook f. in Hook Fl. Brit. Ind. 5, 745, 1890; Bruhl, Guide Orch. Sikkim, 64, 1926; Hegde Orch. Of Arunachal Prad. 62, 1984; Pradhan Ind.Orch.2, 309,1979; Roy, Occurrences: Not common, grows as epiphyte on trees like Bischofia javonica, Salix tetrasperma etc. at a height of 2-4 m. Except for the absence of purplish-brown blotch on the lip, the detailed description of this taxon conforms to that provided by Hooker 5, 750; Bruhl, 64; Pradhan, 2, 305; Roy, 58; Barua,163. The factors responsible for the variant lip are however, not clearly understood. It may be also a variety D. fimbriatum.
Fig. 6. Dendrobium nobile Lindl. Fig. 4. Dendrobium fimbriatum Hook. f.: A, Habit; B, Raceme; C, Perigone; D, Lip; E, Column. Fig. 5. Dendrobium fimbriatum Hook. f. Fig. 7. Dendrobium nobile Lindl.: A, Habit; B, Flower; C, Perigone; D, E, Lip; F, Column; G, Fruit.
Dendrobium nobile Lindl in Hook. in Fl. Brit. India, 5, 740, 1890; Bruhl, Guide. Orch. Sikkim, 65, 1926; Hegde, Orch. Arunachal Prad., 64, 1989; Pradhan, Ind. Orch., 2, 315, 1979; Roy, Orch. India, 60, 1979; Banerji, Orch. Nepal, 64, 1978; Pottinger, Orch., 27, 1990; Rittershausen, Orch., 80, 1999; Novak, Pict. Enclopadia, 502, 1965; Kumar et Monilal, Cat. Ind. Orch., 71, 1994. Stems pseudobulbus, 30-70 cm long, some times more, erect or pendulous, tufted, slightly compressed laterally, yellowish green on maturity. Leaves many, 8-12 x 2.5-3 cm, persistant, ovatelanceolate, apex unequally bilobed. Flowers 1-4, arranged on short peduncles at nodes, 5-7 cm across, white merging with purple at apex, wavy in texture. Sepals linear-oblong, obtuse, 3 x 0.9 cm. Petals much broader, 3 x 1.5 cm. Lip purple at tip with a deep purple central blotch in the middle, 3.5 x 2.5 cm. Anther purple. Fruit 11 x 2.5 cm. (Figs. 6, 7) Flowering time: March-April Occurrence: Not common, grows as epiphyte on trees like Salix tetrasperma, Terminalia myriocarpa etc., at a height of approximately 5-6 m. Fig. 9. Dendrobium transparens Lindl.: A, Habit; B, Receme; C, Perigone; D, E, Lip; F, Column; G, Fruit. Dendrobium transparens Lindl, in Hooker Fl. Brit. Ind. 5, 738, 1890; Pradhan Ind. Orch.2, 316, 1972; Roy, Orch. Ind., 60, 1979; Banerji, Orch. Nepal, 65, 1978; Bruhl, Guide Orch. Sikkim, 64, 1926; Kumar et. Monilal, Cat. Ind. Orch., 72, 1994. Stem pseudobulbus, 30-60 cm long. Leaves 7.5-10 x 1.2 cm, linear, lanceolate, acute. Flowers on leafless stem, 2-3 each node, 4-5 cm across. Sepals and Petals white purple tinged at tips; sepals lanceolate, acute 2.8-3 x 1.3 cm. Lip 3.2 x 1.9 cm, white with large purple patch on the disc. Fruit 6 x 1-1.5 cm. ( Figs. 8, 9) Flowering: April-May Fig. 8. Dendrobium transparens Lindl. Occurences: Common, grows as epiphyte on trees like Salix tetrasperma, Terminalia myriocarpa, Premma bengalansis etc. nearly 4-7 m above ground.
Dendrobium lituiflorum Lindl, in Hook. Fl. Brit. Ind. 5, 740,1890; Hegde, Orch. of Arunachal Prad. 63, 1984; Pradhan, Ind. Orch., 2, 361, 1979; Kumar et. Monilal, Cat. Ind. Orch., 71, 1994; Barua, Orch. Fl. Kamrup Dist., 174, 2001. Stem pseudobulbous, up to 60-80 cm long, pendulous, slender, internodes 2-3 cm. Leaves 7.5-10 x 1.6-2 cm, linear-lanceolate, daeciduous, absent at the time of flowering. Flowers 2-5, in fascicles, 4-5 cm across, pale-purple. Sepals oblong-lanceolate, acute, 3.0 x 1.0 cm, purple, whitish below. Petals ovate-oblong, acute, 3.0 x 1.7 cm, purple, white at the base. Lip 3.5 x 2.5 cm long, trumpet shaped with orbicular mouth, white to pale purple at tips, with purple disc. Fruit 5-5.5 cm long. (Fig. 10, 11) Flowering: March- May Occurences: Frequent, grows as epiphyte on trees like Salix tetrasperma, Terminalia myriocarpa, Premna bengalansis etc. 4-6 m above ground level. Fig. 10. Dendrobium lituiflorum Lindl. Dendrobium aphyllum (Roxb) Fisher, in Gamble, Fl. Press. Madras 3, 1416, 1928; Hook, Fl. Brit. Ind. 5, 738, 1890; Hedge, Orch. of Arunachal Prad. 60, 1984; Pradhan, Ind. Orch,2, 321, 1979; Roy, Orch. Ind. 60, 1979; Banerji, Orch. Nepal, 64, 1978,; Kumar et. Monilal, Cat. Ind Orch; 70, 1994; Barua, Orch. fl. Kamrup Dist; 169, 2001. Plans with pseudobulbs. Stem 60-120 cm long, internodes 3-4 cm long, pendulous, leafless when flowering. Leaves deciduous, sessile, base sheathing. Flowers 1-3 each node, pale rose, 4.5-5 cm across. Sepals sub-equal, oblong lanceolate, sub-acute. Petals broader, elliptic, rounded. Lip yellow, pubescent, 3-3.5 x 1.5-2.2 cm, orbicular at the base, shortly convoluteciliate, pale yellow with radiating streaks at the base. Fruits 6-7 x 0.8 cm long. Fig. 11. Dendrobium lituiflorum Lindl.: A, Habit; B, Receme; C, Perigone; D, E, Lip; F, Column; G, Fruit. The species occurs as two varieties as distinguished by Baruah (2001) on the basis of their leaf characters (Fig. 12). The varieties were earlier reported from Kamrup district.
Fig. 13. Dendrobium aphyllum (Roxb.) Fishcher var. aphyllum: A, Habit; B, Receme; C, Flower; D, Perigone; E, F, Lip; G, Column; H, Fruit.. Fig. 14. Dendrobium aphyllum (Roxb.) Fishcher var. katakinum Iswar Barua: A, Habit; B, Receme; C, Flower; D, Perigone; E, F, Lip; G, Column.
Pseudobulbous stems pendulous. Leaves shorter at the base of the stem and gradually longer towards the apex; basal leaves ovateelliptic, sub-orbicular, 3-4 x 2 cm with rounded or sub acute apex; apical leaves ovate, lanceolate oblong with acute or acuminate or sub-acuminate apex, 8.0 x 3.0 cm. Lateral sepals slightly keeled abaxially along mid vein, elliptic oblong, slightly falcate. Lip with 5 purple nerves. (Fig. 13) Flowering: May Occurrences: Not common, grows on trees like Lagertromia flosrefgine, Bischofia javonica, Premna bengalansis etc. at a height of 2-4 meter. Dendrbium aphyllum (Roxb) Fischer ver. Aphyllum Fig. 12. Dendrobium aphyllum (Roxb.) Fishcher: A, var. aphyllum; B, var. katakinum Iswar Barua. Present collection of these varieties from the National Park extends their distribution range to Upper Assam. Keys to varieties A B Leaves ovate-lanceolate, oblong through out the stem, acute or acuminate the apex, 5-12 x 3-4 cm; decreasing in length upward along the stem. Sepals oblong-lanceolate more or less falcate not keeled. Lip with distinct ridges. (Fig. 14) Flowering time: May -June Ocurrences : Common, grows on trees like Lagerstromoa flosregine, Bischofia javonica, Premna bengalansis etc. at a height of 2-4 m. (a) Leaves ovate-elliptic or sub orbicular and much shorter along the base of the stem, ovate lanceolate to oblong and longer towards the apex. Dendrobium aduncum Wall. in Hook., Fl. Brit. Ind. 5,730, 1890; Bruhi, Guide Orch. Sikkim, 60,1926; Pradhan Ind. Orch.2, 324,; Kumar et. Monilal,Cat. Ind. Orch., 70, 1994. (b) ver. katakinum Leaves ovate lanceolate and oblong, decreasing length to the upward along the stem. ver. aphyllum Dendrbium aphyllum (Roxb) Fischer ver. katakinum Iswar Barua. Plants with pseudobulbous stems, pendulous, 30-90 cm. long, sometimes more. Leaves many, 5-7.5 x 1-1.8 cm, linear-lanceolate, acute-acuminate, minutely and unequally bifid at apex. Inflorescence zigzag racems, each with 4-9 flowers. Flowers 1.2-2.0 cm across, pale purple. Dorsal sepals ovate, acute 1.5 x 0.8 cm, lateral sepals triangular, sub rhomboidal, 1.6 x 1.3 cm. Petals 1.5 x 0.8 cm, broader than sepals. Lip 1.2 x 0.9 cm, cymbiform, cuspidate, ciliate, adpressed to the
concave column; pubscent except for a squarish glistening area on the disc. Column foot long; mentum saceate. Anther papilliose, dark purple. (Fig. 15, 16) Flowering: May-June Occurrence: Not common, epiphyte on trees like Salix tetrasperma, Bischofia javonica, Premma bengalansis etc. at a height of 2-4 m above ground level. Conclusion Fig. 15. Dendrobium aduncum Wall. Fig. 14. Dendrobium aduncum Wall.: A, Habit; B, Receme; C, Flower; D, Perigone; E, F, Lip; G,H, Column. The forests of Assam support a large number of beautiful and important Orchids. Though some information is available on these plants, but studies related to their conservation and commercialization are meager. Incidentally, unregulated forest felling has led to depletion of orchid habitats. The orchids are also faced with heavy collection pressures for economic purposes. Consequently, their natural populations are declining rapidly. Orchid flora of Dibru-Saikhowa National Park and Biosphere Reserve (35 species) is a valuable natural resource. It needs to be properly investigated, evaluated, and listed for sustainable commercial use. Presently, 7 species of floriculturally significant Dendrobes (Dendrobium moschatum, D. fimbriatum, D. nobile, D. transparens, D. lituiflorum, D. aphyllum, D. aduncum) were collected from Dibru- Saikhowa National Park and Biosphere Reserve. Some of these (D. fimbriatum, D. nobile, D. aphyllum var. katakinum,, D. aduncum) are not common and need to be conserved for sustainable use in Assam. Incidentally, the present studies though they represent an embodiment of a work of limited magnitude, are of considerable academic, explorative and informative value. While a featured study of the present nature is expected to reveal the richness or otherwise of a taxon besides adding to the available information, a continued and in-depth study is bound to yield extremely useful data on the rich flora of the entire forested area. However, as most of the areas in the National Park are
yet to be properly explored for their orchid wealth, further studies are suggested. Acknowledgement I extend my sincere gratitude to Prof. Dr. Prokash Kotoky, Head, Department of Botany, Sibasagar College, Joysagar, Assam for constant supervision and valuable suggestions during the course of present studies. I am also thankful to the authorities of Saikhowa Wildlife Range for facilities. References Banerji, M.L., 1978. Orchids of Nepal. Bishen Singh Mahendra Pal Singh, Dehra Dun, India. Barua, I. C. 2001. Orchid Flora of KamrupDistrict. Bishen Singh Mahendra Pal Singh, Dehra Dun, India. Bruhl, P., 1926. A Guide to the Orchid of Sikkim. Thacker & Spink & Co., Simla, India. Gamble, J.S. 1928. Flora of presidency of Madras. Vol-III. Adlard and Sons Ltd.,London. Hegde, S. N.1984. Orchids of Arunachal Pradesh. Govt. of Arunachal Pradesh, Itanagar, India. Hooker, J. D.1890. Orchidaceae. In: Flora of British India. Vol-5. pp. 687 864. L.Reeve and Co., Ashford, Kent. Mahanta, N. 2002. Unfolding the Forest and Wildlife of Tinsukia Dist. in: Souvenir Dehing Patkai Festival. pp. 86-90. Assam, India. Novak, F.A. 1965. The Pictorial Encyclopedia of Plants and Flowers. pp. 492-506. Pradhan, U.C. 1979. Indian Orchids Guide to Identificationand Culture. Vol-II. Kalimpong, India. Rittersheusen. 1997. Success with Orchids. Twickenumh. Roy, A.S. 1979. Orchids of India. National Book Trust. New Delhi, India. Sarmah, N. 2003. Dibru-Saikhowa National Park and its Salient Features in: Souvenir Dehing Patkai Festival. pp. 91-93.Assam,India.