ICSSR Sponsored National Seminar
Emerging Trends in Environment Conservation Public Awareness
9th April, 2022 Seminar Paper
On
Diversity of Dendrobium Orchid Species of Dulung Reserve Forest of Lakhimpur District of Assam
Jully Gohain Neog, Assistant Professor, Dept. of Botany, L.T.K. College, Azad, North Lakhimpur, Assam
Abstract
Orchids, the most beautiful creations of God comprised a unique group of plants belonging to family Orchidaceae. Taxonomically, they represent the most highly evolved family among monocotyledons with specializations and modification in their vegetative and floral characters form an integral part of the wonderful natural heritage. Most of the orchids are tropical, while some others are found even in Arctic regions. There are about 19,500 species grouped in about 760 genera which are distributed all over world. Dendrobium is one of the largest orchid genus with more than 1500 species distributed in the Asiatic tropics, India, Burma, Thailand, Malyasia, Philipines, Sumatra, Australia and eastward to Fiji (Mukharjee, 1983). In India 165 species of Dendrobium have been reported, which has an incredible range of diversity in size, shape, structure, number, density, colour, fragrance of their flowers (Hegde, 1984). Recently 20 species of Dendrobium have been reported in Assam (Barua, 2001). Dulung Reserve Forest is one of the major centers of Orchid diversity. In the process of exploring the orchid flora of this forest, high genetic diversities have been observed in the species of Dendrobium. These diversities not only include the morphological parameters but also the floral characters.
Keywords: Dendrobium, Dulung Reserve Forest, Genetic diversity, Orchid
INTRODUCTION
Orchids, the most beautiful creations of God comprised a unique group of plants belonging to family Orchidaceae. The term “Orchid” was derived from Greek word “Orchis” meaning testicle like and was first coined by Theophrastus (370-285 BC). Taxonomically they represent the most highly evolved family among monocotyledons with specialization and modification in their vegetative and floral characters form an integral part of the wonderful natural heritage. Orchids are regarded as the most exhilarant flowers of world because of their unique colour, strange and beautiful shape, size, long lasting quality, alterative odour and diversity of habit and habitat. There are about 20,000 species grouped in about 750 genera which are distributes all over world. In India, from ancient i.e. from the time of Ramayana and Mahabharata, the orchids were known as the plants for ornamentation and believed to be the symbol purity. India is considered as a rich orchid heritage with about 1350 species under 167 genera. The North Eastern region harbours about 72% species that covers about 900 species under 145 genera. Assam, the second largest state of N.E. India occupies the seventh position in terms of orchid diversity and exhibits about 193 species of orchids under 71 genera. Dendrobium is one of the largest orchid genus with more than 1500 species distributed in the Asiatic tropics, Burma, Thailand, Malaysia, Philippines, Sumatra, Australia and Eastward to Fiji (Mukherjee, 1983). In India, 165 species of Dendrobium have been reported, which has an incredible range of diversity in size, shape, structure, number, density, colour and fragrance of their flower (Hegde, 1984). The word Dendrobium is derived from the two Greek words “Dendron” tree and “bios” life, meaning “living on tree” which reflect the epiphytic nature of the genus. Recently 20 species of Dendrobium have been reported in Assam (Barua, 2001) out of these, many species are observed to be present in the Dulung Reserve Forest. In the process of exploring the Orchid flora of this reserve forest, high genetic diversities have been reported in this paper. These diversities not only include the morphological parameters but also the floral characters. Therefore the objective of this work is to study the variability of different species in terms of their size, shape, structure, density, colour, fragrance, longevity and flowering season of the flowers, leaf characters and their habit and habitat in the forest. Thus study will help to prepare a detailed monograph on the orchid flora of the Dulung Reserve Forest.
STUDY AREA
Lakhimpur district is situated on the North Eastern corner of Assam. The district lies between 26048⸍-27053⸍ Northern Latitude and 93042⸍-94020⸍ East latitude. The district covers an area of 2,277 sq. km. The present area is Dulung Reserve Forest which is 20 km away from the district headquarter. Dulung Reserve Forest of Lakhimpur district is located at the foothills of Arunachal Pradesh. The forest lies between 27026⸍4⸍⸍-27031⸍4⸍⸍ Northern latitude and 9407⸍28⸍⸍-94018⸍2⸍⸍ East longitude (approx.). The climate of this area can be distinguished as tropical. The rainfall is fairly distributed throughout the year except in the winter and somewhat heavy during the month of June (900mm.). The minimum temperature is 180C and maximum temperature is 360C. The relative humidity in this area lies between 90-95%. The vegetation of Dulung R. F. is tropical semi evergreen whereas the type of soil is old alluvium.
Boundary of Dulung Reserve Forest
North- Dulung River and Dulungmukh
South- Rajgarh Ali, Pathalipam and NH15
East- Subansiri River, Gerukamukh
West- Boginodi, Serajuli
Total area- 9900.03 hec.
MAP
MATERIALS AND METHODS
The study was conducted in Dulung Reserve Forest during January 2021-March 2022. Extensive field surveys were conducted in the Reserve forest by traversing on foot in every month. During the study stress was laid to orchid species in their flowering condition so as to identify them properly. Collected specimen were dried and poisoned in saturated solution of mercuric chloride and dissolved in absolute alcohol for the preparation of herbarium sheet (Rao and Sharma, 1990). For identification of orchid species, morphological parameters and floral characters were observed in wild condition. The collected orchid species planted in the orchidarium. Flowers are photographed and identification was done by consulting with “Orchid flora of Kamrup district” by I.C. Baruah, 2001, “Orchid of Arunachal Pradesh” by Sadanand N. Hegde, 1984 etc. and photo specimens were sent to the Botanical Survey of India, Eastern circle, Shillong.
RESULTS
The following species of Dendrobium were found during field study in Dulung Reserve Forest.
i) Dendrobium aduncun Wall. : Stems slender with small pseudobulb. Leaves linear-oblong, 6.8×1.1cm. Inflorescence 2.5cm long with 4 flowers. Flowers pale purple, lip greenish creamy, one purple blotch in the middle. Lasting for about 4 days, sweet scented. Flower size 2.1 cm.
Month of flowering-May-June. Habitat-Epiphytic.
ii) Dendrobium lituiflorum Lindl. : Stems slender, pendulous, Leaves linear-oblong, absent during flowering, 7×1.4cm, Inflorescence 25cm long with 22 flowers, Flowers whitish purple, lip deep purple with transverse purple streaks at base, trumpet shaped, lasting for about 16 days, scentless, Flower size 5cm across. Month of flowering- March-April, Habitat-Epiphytic.
iii) Dendrobium aphyllum (Roxb.) Fisher Var. aphyllum: Stems elongate, jointed, cylindric. Leaves ovate-lanceolate, acute at apex, 7.5×2.3cm. Inflorescence 28cm long with 20 flowers. Flowers pinkish white, lip sub-orbicular with a shortly clawed convolute base, pubescent; pale yellow with 3 transverse purple streaks. Lasting for about 9 days, scentless, Flower size 4.8cm across.
Month of flowering- March-April and May-June. Habitat- Epiphytic.
iv) Dendrobium aphyllum (Roxb.) Fischer var. Katakinum Iswar Barua: Stems elongate, jointed, cylindric, basal leaves ovate-elliptic to sub-orbicular, rounded or subacute apex, 7.1×2.3cm. Inflorescence 32cm long with 26 flowers. Flowers pinkish white, lip sub-orbicular with a shortly clawed convolute base, pubescent, pale yellow with transverse purple streaks. Lasting for about 11 days, Scentless, Flower size 4.7cm.
Month of flowering-May-June, Habitat-Epiphytic.
v) Dendrobium moschatum (Buch-Ham.) Sw. var. moschatum: Robust tufted epiphytes, Stem stout, Leaves oblong, lanceolate, acute at apex, 14×3.5cm, Inflorescence 12cm long with 9 flowers. Flowers creamy with purplish tinge on petals and sepals with reddish veins, lip hemispherical or pear shaped open mouthed pouch with two large dark maroon blotches. Lasting for only 1 day, Sweet scented. Flower size-5.2cm across.
Month of flowering- May- June. Habitat: Epiphytic.
vi) Dendrobium moschatum (Buch-Ham.) Sw. var. Unquipetalum Iswar Barua: Robust tufted epiphytes, Stem stout, Leaves oblong, lanceolate, acute at apex, 14×3.2cm, Inflorescence 13cm long with 7 flowers. Flowers creamy with purplish tinge on petals and sepals with reddish veins, lip slipper shaped with two large dark maroon blotches. Lasting for only 1 day, Sweet scented. Flower size-4.8cm across.
Month of flowering- May- June. Habitat: Epiphytic.
vii) Denrobium nobile Lindl. : Stem erect, tufted, slightly compressed. Leaves persistent, ovate, lanceolate obliquely notched at apex, 12×2.1cm. Inflorescence 21 cm long with 11 flowers. Flowers white merging with purple at the apex, wavy in texture. Lip is purple at tip, white in the middle followed by pale yellow and with deep purple central blotch. Lasting for about 8 days, scentless, flower size 3.7 cm across.
Month of flowering- March-April. Habitat-Epiphytic.
viii) Dendrobium transparens Lindl. : Pseudobulbs are slender, erect, smooth, leaves linear lanceolate, 8×1.5 cm. Inflorescence 23cm long with 20 flowers. Flowers white suffused with pink. The lip is downey, suppressed bears as purple lines towards the base. Lasting for 12 days, scentless, flower size 4.2 cm across.
Month of flowering- April. Habitat-Epiphytic.
ix) Dendrobium fimbriatum Hook: Stem cylindrical, stout, leaves oblong, lanceolate, acuminate, 14×3 cm. Inflorescence pendulous, 14 cm long having 15 flowers. Flowers yellow lip, sub orbicular, densely tomentose, yellow with a deep purplish brown blotch in the middle and reddish, streaks at base, margins fimbriate wavy. Lasting for about 11 days, sweet scented. Flower size 4.5 cm across.
Month of flowering- April. Habitat-Epiphytic.
x) Dendrobium cumulatum: Pseudobulbs erect, leaves oblong acute, 12×2.6 cm. Inflorescence 5 cm long, 4 flowered. Flowers whitish pink. The lip is white flushed purple, its base elongated backwards like a spear. Lasting about 15 days, sweet scented. Flower size 2.4 cm across.
Month of flowering- June-July. Habitat-Epiphytic.
xi) Dendrobium salcatum: Stem stout, erect, compressed, leaves broadly elliptic, coraceous, 12.2×4.9 cm. Inflorescence 9 cm long with 10 flowers. Flower pendent, yellow, lip broadly ovate, clawed, orange yellow with a patch of brownish nerves on either side at the basal part. Lasting about 10 days, sweet scented, Flower size 3 cm across.
Month of flowering- June-July. Habitat-Epiphytic.
xii) Dendrobium fugax Reichb. : Stem long with semi erect and pendulous branches cylindric, unileaved. Leaves solitary, oblong lanceolate, obtuse 13×1.3 cm. Flower 1 or 2, either axial or abaxial at the base of the leaves. Flower small, white, lip arrow shaped, 3 lobed with cuneate narrow base, lasting for 1 day, scentless, flower size 2 cm across.
Month of flowering- January, April, July, October. Habitat-Epiphytic.
Table-1: “Morphological parameters” including the habitat of 12 Dendrobium Species of orchid of Dulung Reserve Forest of Lakhimpur District.
Photo No
Name of the Species
Leaf Length in cm
Leaf Breath in cm
Length of Inflorescence in cm
No of flower per spike
Flower colour
Diagnostic character of Labellum (Lip)
Scent
Lasting of flower (in days)
Size of flower in cm
Month of flowering
Habitat
1
Dendrobium aduncun Wall.
6.8
1.1
2.5
4
Pale Purple
Lip greenish creamy, one blotch
Scented
4
2.1
June
Epiphytic
2
Dendrobium lituiflorum Lindl.
7
1.4
25
22
White with deep purple lip
Lip trumpet shaped, largely orbicular
Scentless
16
4.9
March
Epiphytic
3
Dendrobium aphyllum (Roxb.) Fisher Var. aphyllum
7.5
2.3
28
20
Pinkish white
Lip sub-orbicular, pubescent, 3 purple nerves inside the excavation of the claw
Scentless
9
4.8
March-April, May-June
Epiphytic
4
Dendrobium aphyllum (Roxb.) Fisher Var. Katakinum Iswar Barua
7.1
2.3
32
26
Pinkish white
Lip sub-orbicular, pubescent, 5 purple nerves inside the excavation of the claw
Scentless
9
4.7
May-June
Epiphytic
5
Dendrobium moschatum (Buch-Ham.) Sw. Var. moschatum
14
3.5
12
9
Creamy with purplish tinge
Lip hemispherical or pear shaped with two large dark maroon blotches
Scented
1
5.3
May-June
Epiphytic
6
Dendrobium moschatum (Buch-Ham.) Sw. Var. unquipetalum Iswar Barua
13
3.2
13
7
Creamy with purplish tinge
Lip slipper shaped with two large dark maroon blotches
Scented
1
5
May-June
Epiphytic
7
Dendrobium nobile Lindl.
12
2.1
21
11
White merging with purple
Lip sub-orbicular with deep purple blotch
Scentless
8
3.7
March-April
Epiphytic
8
Dendrobium transparens Lindl.
8
1.5
23
20
White suffused with pink
Lip downey, suppred bears as purple lines towards the base
Scentless
12
4.2
April
Epiphytic
9
Dendrobium fimbriatum Hook
13.2
3
14
15
Yellow with a deep purplish brown blotch
Lip yellow, sub-orbicular, densely tomentose
Scented
11
4.5
April
Epiphytic
11
Dendrobium cumulatum
12
2.6
5
4
Whitish pink
Lip white flushed purple
Scented
15
2.4
June-July
Epiphytic
11
Dendrobium salcutum
12.2
4,9
9
10
Yellow with orange yellow
Lip broadly ovate, clawed
Scentless
10
3
June-July
Epiphytic
12
Dendrobium fugax Reichb. f.
13
1.3
2
White
Lip arrow shaped with cuneate narrow base
Scentless
1
2
January, April, July, October
Epiphytic
DISCUSSION:
Dendrobium occurs in diverse habitats. All the species of Dendrobium are epiphyte on water loving species. They grow well on Lagerstroenia speciosa (Ajar), Polyatthia longifolia (Devadaru), Bischofia javanica (Uriam), Premna bengalensis (Gohara), Artocarpus heterophyllus (Kathal) etc. Diversity in the size of the leaf is observed in the leaf of the twelve species of Dendrobium genus. The biggest leaf size is found in Dendrobium moschatum (Buch-Ham.) Sw. Var. moschatum (14×3.5 cm) and the leaf size of the Dendrobium moschatum (Buch-Ham.) Sw. Var. unquipetalum Iswar Barua, Dendrobium fimbriatum Hook, Dendrobium fugax, Dendrobium cumulatum, Dendrobium nobile is almost similar with 13.2×3cm, 13×1.3cm, 12.2×4.9cm, 12×2.1cm, respectively. The leaf size of Dendrobium transparens holds the 3rd position in leaf size which measures 8×1.5cm. The leaf size of Dendrobium lituiflorum is smaller than two variety of Dendrobium aphyllum. The smallest leaf size is found in Dendrobium aduncun. The flower of Dendrobium moschatum (Photo no 5) exhibit the largest size (5.3 cm), which is last for one day. The flower size of Dendrobium fugax is 2cm which is smallest of all. The flower sizes of other species are Dendrobium lituiflorum 4.9cm, D. aphyllum (Roxb.) Fisher var. aphyllum 4.8 cm, D. aphyllum (Roxb.) Fisher Var. Katakinum Iswar Barua 4.7 cm, D. moschatum (Buch-Ham.) Sw. Var. unquipetalum Iswar Barua 5 cm, D. fimbriatum 4.5 cm, D. transparens 4.2 cm, D. nobile 3.7 cm, D. cumulatum 2.4 cm, D. salcatum 3 cm, D. aduncun 2.1 cm.
Dendrobium aphyllum (Roxb.) Fisher Var. aphyllum and Dendrobium aphyllum (Roxb.) Fisher Var. Katakinum Iswar Barua are the most common species. They are purely epiphytic in nature and grow best on various plants. The propagation rate is highly encouraging. D. aphyllum (Roxb.) Fisher var. aphyllum is bloom in two seasons in one calendar year; one is March-April and the other one is May-June. Among 12 species of Dendrobium species found in the reserve forest, D. moschatum (two varieties) has good resistence capacity. It is sun loving species and it can grow even on concrete substratum. The propagation rate of this species is also high. The only drawback of this species is that full bloom flower lasts only for a single day.
In fact the floral and vegetative character exhibits considerable genetic diversity (Mukherjee, 1983). The documented species show greater variability in flower size, colour, number and longivity which may provide the source of parental genotype for hybridization (Rao, 1979). The study may help to measure the genetic diversity among the species to determine inter-relationship among then.
Photographs of 12 Dendrobium orchid species of Dulung Reserve Forest
(1) (2)
(3) (4)
Fig: 1. Dendrobium aduncun Wall. 2. D. lituiflorum Lindl. 3. D. aphyllum (Roxb.) Fisher Var. aphyllum, 4. D. aphyllum (Roxb.) Fisher Var. Katakinum Iswar Barua
(5) (6)
(7) (8)
Fig: (5) D.moschatum (Buch-Ham.) Sw. var. moschatum (6) D. moschatum (Buch-Ham.) Sw. var. unquipetalum Iswar Barua, (7) D. nobile Lindl. (8) D. transparens Lindl.
(9) (10)
(11) (12)
Fig: (9) D. fimbriatum Hook. (10) D. cumulatum (11) D. salcatum (12) D. fugax Reichb.f.
CONCLUSION:
Dulung Reserve Forest of Lakhimpur district is situated at the foot hills of Arunachal Pradesh. Being located in the foot hills of Arunachal Pradesh, the micro climate prevalent in this reserve forest like light and shade condition, temperature, humidity, soil type and tecture, mycorrhiza, presence of pollinating vectors, etc influence the occurrence and distribution of diverse orchid flora (Hegde,1985).
But it is very sad to think that man is unwilling to value the orchids and that is why it is decreasing from nature day by day. It is known for the local inhabitant of this forest that local healers of different places collect orchid species viz, D. lituiflorum, D. aphyllum for medicinal purpose by paying a small amount (viz. @Rs.10 per kg) to the villagers.
Deforestration is one of the major problems of this forest which should be prevented. Every year about thousand of plants are cut down by the people, which are leading to the disturbance of orchid habitat. Besides people from border areas are encroaching greater area. They are cultivating rice, pineapple, ginger, turmeric etc and so a great area is destroyed. As a result habitats of many epiphytic and terrestrial orchids are destroyed. In recent year a link road was constructed from NH15 to Gerukamukh to Dulung Reserve forest. Owing to that a large number of trees were destroyed, resulting to loss of habit of epiphytic orchids.
Due to these causes the numbers of orchids of this reserve forest is decreasing in natural wild state. Hence, to save them from some threatening conditions there is an urgent need to conserve these orchid species through in-situ and ex-situ conservation for future generation.
REFERENCES:
1. Barua, I.C. 2001, Orchid flora of Kamrup district of Assam. Bishen Singh Mahendra Pal Singh, Dehradun.
2. Bharali, Popi Santana 2005, Genetic diversities of Dendrobium species available in the Dibru Saikhowa Biosphere reserve. Popi Santana Bharali Rachna Sambhar, Banalata, Dibrugarh.
3. Ghose, B.N. 1968, Beautiful Indian Orchids. G. Ghose & Co. Darjeeling.
4. Hegde, S.N. 1984, Orchids of Arunachal Pradesh, Govt. of Arunachal Pradesh, Itanagar.
5. Neog, J.G. Gogoi, A.J. 2018, Baichitramoy Orchids, published by L.T.K. College publication cell, North Lakhimpur.
6. Rao, A.S. 1994 Orchids of India, N.B.T. New Delhi.
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