Orchidaceae is a diverse family of flowering plants with several general characteristics:

1. Epiphytic or Terrestrial: Orchids can be epiphytic, growing on other surfaces like trees, or
terrestrial, growing in the ground.
2. Bilateral Symmetry: Flowers typically exhibit bilateral symmetry, meaning they can be
divided into two identical halves.
3. Complex Flowers: Orchid flowers are often complex, with a specialized lip (labellum),
column, and modified petal structures.
4. Specialized Pollination Mechanisms: Many orchids have unique mechanisms for pollination,
often involving specific insect or bird interactions.
5. Single Ovary: Orchids have a single, superior ovary. This distinguishes them from other
related plant families.
6. Fused Petals and Sepals: The petals and sepals are usually fused, forming a structure called
the perianth.
7. Pollinia: Orchids often have pollinia, which are masses of pollen grains that stick together.
They aid in efficient pollination.
8. Mycoheterotrophy: Some orchids are mycoheterotrophic, relying on fungi to obtain nutrients
instead of photosynthesis.
9. Varied Growth Forms: Orchids exhibit diverse growth forms, from tiny species to large,
showy ones.
These characteristics contribute to the uniqueness and adaptability of the Orchidaceae family.

The inflorescence of Orchidaceae is typically a distinctive structure called a *raceme*. A

raceme is an unbranched, elongated cluster of flowers along a central axis. Each flower is
attached by a stalk (pedicel) to the main stem (rachis) of the raceme.
In some orchids, variations of the raceme exist, such as:
1. *Panicle:* A branched inflorescence with multiple racemes.
2. *Spadix:* A dense, spike-like inflorescence often enclosed by a modified leaf called a spathe.
The arrangement and appearance of orchid flowers on the inflorescence can vary widely among
species, contributing to the diversity within the Orchidaceae family.

References
HAGERMAN, G., AND K. SMITH. 1993. A new weather station on Carrie Bow Cay. In K.
Ru¨tzler, K. Smith, and S. Klontz [eds.], Caribbean coral reef ecosystems: 1993 report, 4.
National Museum of Natural History, Smithsonian Institution, Washington, DC.
HARPER, J. L. 1977. Population biology of plants. Academic Press, New York, NY.
P. H. LOVELL, AND K. G. MOORE. 1970. The shapes and sizes of seeds. Annual Review of
Ecology and Systematics 1: 327–365.
HOWE, H. F., AND J. SMALLWOOD. 1982. The ecology of seed dispersal.
Annual Review of Ecology and Systematics 13: 201–228.
JANZEN, D. H. 1970. Herbivores and the number of tree species in tropical forests. American
Naturalist 104: 501–528.
MURREN, C. J., AND A. M. ELLISON. 1996. Effects of habitat, plant size, and floral display
on male and female reproductive success of the neo-tropical orchid, Brassavola nodosa.
Biotropica 28: 30–41.
NIKLAS, K. J. 1992. Plant biomechanics. University of Chicago Press, Chicago, IL.
OKUBO, A., AND S. A. LEVIN. 1989. A theoretical framework for analysis of wind dispersal
of seeds and pollen. Ecology 70: 329–338.
PASQUILL, F., AND F. B. SMITH. 1983. Atmospheric diffusion, 3rd edition. Ellis Horwood,
Chichester.
WILKINSON, L., M. HILL, J. P. WELNA, AND G. K. BIRKENBEUEL. 1992.
SYSTAT for Windows, Version 5. SYSTAT, Evanston, IL.
WILLSON, M. F. 1983. Plant reproductive ecology. Wiley, New York, NY. 1993. Dispersal
mode, seed shadows, and colonization patterns.

REVIEW WORK FAMILY Orchidaceae OF MORPHOLOGICAL CHARACTERS

INTRODUCTION
Orchids are the second largest families of flowering plants (after Asteraceae) [1] and are
distributed throughout the world. The family orchidaceae is divided into five subfamilies
(Apostasioideae, Cypripedioideae, Vanilloideae, Orchidoideae, Epidendroideae). Orchids
account for c. 8% of angiosperm species diversity [2]. Till date, 29,199 species have been
identified and accepted [3], although several hundred new species are added each year. By the
end of 2017, the IUCN Global Red List included assessments for 948 orchid species, of which
56.5% are reported to be threatened [4]. Orchids are monocot plants.
1. Willis KJ. (ed). State of the world’s plants. Report. Royal Botanic Gardens, Kew, 2017.
2. Chase MW, Cameron KM, Freudenstein JV, Pridgeon AM, Salazar G, Berg C, et al. An
updated classification of Orchidaceae. Botanical Journal of the Linnean Society. 2015;
177:151-174.
3. Govaerts R, Bernet P, Kratochvil K, Gerlach G, Carr G, Alrich P, et al. World checklist of
Orchidaceae, 2017. Kew: Facilitated by the Royal Botanic Gardens. Available at:
http://apps.kew.org/wcsp/.
4. IUCN. The IUCN Red List of Threatened Species, Version 2016-3, 2017. Available at:
www.iucnredlist.org.
Orchids represent one of the largest and most widely distributed families of flowering plants,
numbering >28,000 species (Givnish et al., 2015; Royal Botanic Gardens, 2021), and orchid
harvest and trade is equally diverse. It includes thousands of species harvested as ornamentals
for backyard gardens and specialist hobbyist collections (e.g., Flores-Palacios and Valencia-
Diaz, 2007; Phelps and Webb, 2015), and for cultural or religious celebrations (e.g., Emeterio-
Lara et al., 2016; Ticktin et al., 2020).
Eg: Edible species of Orchid such as Chikanda cake (Veldman et al., 2018), salep beverage,
dondurma/kaimaki ice-cream (Hossain, 2011; Tamer et al., 2006), and vanilla ice-cream (Ecott,
2004). Many species with medicinal properties are also found, such as Dactylorhiza hatagirea,
whose tubers are used in Ayurveda, Siddha, Unani, and Himalayan folk medicinal traditions
(Wani et al., 2020), and Dendrobium sp. used in traditional Chinese Medicine (Liu et al., 2014).

The oldest record of orchids in India is by Charak, who in A.D.100 in his classical book on
herbal medicines- ‘Charak Samhita’ mentioned medicinal properties of various indigenous
herbs including ‘Vanada’- a vandaceous plant and several other which are very much similar
to present day genera like, Flickingeria, Malaxis, Eulophia, etc. But the first scientific account
of Indian Orchids came through in the 17 th century by van Rheede, the then Dutch Governor
of Malabar in his classical work ‘Hortus Malabaricus’ (1635- 1691). Rheed for the first time
described and illustrated a number of orchid species and also the genera like Acampe,
Bulbophyllum, Cymbidium, Dendrobium, Eulophia, Liparis, Malaxis, Rhynchostylis, Vanda,
etc. from Malabar region of India.

Distribution of Orchids in India Based on the altitude the orchid distribution in India can be
categorized into the following 4 zones but many species overlap these zones:
1-Tropical Zone (from sea- level to 1000 m): It has two distinct sub-zones –
a) Extending from sea level up to about 500m, this region has lesser rain fall and the summer
temperature in many places reaches as high as 40 C which is not suitable for orchids. However,
areas having sufficient rainfall have forests, which provide conditions for the growth of few
selected orchid species. Few terrestrial forms like species of Arundina, Calanthe, Nervilia, etc.
can be seen growing in open grassy places or under forest cover. Epiphytes such as species of
Acampe, Aerides, Paplionanthe, Rhynchostylis, Cymbidium, Pholidota, Luisia, Vanda, etc. are
seen on the tree trunks of the forests.
b) Lying between 500 to 1000 m, this region in most of the places receives normal to heavy
rainfall and supports tropical humid dense forests. A large number of epiphytic orchids can be
seen growing on the forest trees of which species of Bulbophyllum, Dendrobium, Coelogyne,
Eria, Luisia, Pholidota, Aerides, Ascocentrum, Papilionanthe, Rhyncostylis, etc. are
predominant. In addition, a number of terrestrial and saprophytic forms occur on the moist
shady, humus rich forest floors or in open grassy places.
2- Subtropical Zone (from 1000 to 2000 m): This zone receives lesser rain and supports mixed
forests comprising of tall and medium sized trees forming dense canopy through which little
light penetrates. The relative humidity is very high reaching as up to 100% during rainy season.
The summer temperature varies between 25 to 30 C during day and 18 to 20 C during night.
The winter season is cool and dry having 15 to 20 C day temperature which falls up to 10 C at
night and the precipitation in the form of dew during night and early morning is common. The
tree trunks and rocks are mostly covered with thick moss cover providing very suitable
conditions for the growth of a rich orchid flora. These forests abound in epiphytic species of
which species of Aerides, Acampe, Bulbophyllum, Dendrobium, Eria, Coelogyne, Oberonia,
Paplionanthe, Liparis, Cymbidium, Cleisostoma, Luisia, Flickingeria, Pholidota, Vand, etc. are
most commonly occurring forms many of which prefer open, sun exposed areas, some partially
exposed while many prefer densely shaded areas. Apart from the epiphytes, a large number of
terrestrial orchids are also found growing on the moist, shaded forest floors in this zone of
which Phaius, Anoectochilus, Calanthe, Nervilia, Thunia, Malaxis, Habenaria,
Paphiopedilum, Arundina, Zeuxine, etc. are the most dominant ones. In addition, saprophytic
orchids like Epipogium, Galeola species are also found in this zone. The rare Blue Vanda -
Renanthera imschootiana is known to occur in this zone.
3- Temperate Zone (from 2000 to 3500 m): This zone has cool climate and the region above
2800 m generally experiences snowfall during winter months and often remains covered with
snow for 3-4 months. The winter temperature varies around 10 C whereas summer temperature
generally ranges between 18- 20 C. The humidity is high and ranges from 80 to 100% and fog
and mist are of common occurrence. The forests in this zone are dominated by species of
Quercus, Magnolia, Rhododendron and a number of gymnospermous species of Pinus, Larix,
Tsuga, etc. The tree trunks and their branches are densely covered with thick mossy layer
providing very congenial conditions for epiphytic orchids. Some of the common species found
in this zone are that of- Aerides, Ascocentrum, Bulbophyllum, Dendrobium, Oberonia,
Coelogyne, Cymbidium, Otochilus, Pleone, Gastrochilus, Eria, Vanda, etc. while Calanthe,
Epipactis, Malaxis, Cypripedium, Dactylorhiza, etc. are some prominent terrestrial genera of
this zone.
4- Alpine Zone (from 3500 to 5000 m): Situated in the high Himalayan ranges, this zone
experiences severe cold condition and is covered with snow for about 5-6 months during the
year. The trees are very rare or absent in this zone and the climatic conditions do not support
any epiphytic growth and only few terrestrial species are found growing in this zone such as
species of Cypripedium, Habenaria, Herminium, Dactylorhiza, etc. In India although the
orchids are distributed throughout from the Himalayan region to Andaman and Nicobar Islands,
but the maximum species diversity has been observed in the following four regions:
Himalayan Region:
Eastern Himalaya: Eastern Himalayan region which is also known as the ‘Cradle of
Flowering Plants’ (Takhtajan,1969) includes seven north-eastern states namely-
Arunachal Pradesh, Assam, Meghalaya, Mizoram, Manipur, Nagaland, and Tripura;
Sikkim and Darjeeling district of West Bengal is a distinct phytogeographical region
which has the highest floristic diversity in the Indian subcontinent. This region with
higher precipitation is more humid and is far richer in species diversity and endemic
elements than its Western Himalayan counterpart. The region is dominated by
broadleaved elements like, oaks, rhododendrons, magnolias, laurels, tree ferns, orchids,
 etc. The warm humid climate, high rainfall and dense forests offer most favorable
condition for the growth and development of a rich and diverse orchid flora and it is
not surprising to note that about 900 orchid species find shelter in this region.
Bulbophyllum, Dendrobium, Eria, Habenaria, Coelogyne, Cymbidium, Oberonia,
Liparis, Calanthe, etc. are some of the most dominant genera and as many as 56 genera
viz., Acrochaene, India, Rhomboda, Risleya, Acriopsis, etc. are restricted to Eastern
Himalayan region. Eight of the nine species of lady’s slipper orchid Paphiopedilum
known from India are confined to this region except P. druryi, which is endemic to
Western Ghats. Out of the 8 states falling under Eastern Himalaya, Arunachal Pradesh
has the highest number of more than 630 orchid species followed by Sikkim and
Meghalaya respectively.
North-Western Himalaya: Western Himalayan region, which spreads over from
Uttaranchal (Kumaon & Garhwal) up to Jammu & Kashmir characteristically differs
from Eastern Himalaya in having cool dry climate and less rain fall which further
decreases as one moves towards western side. This region abounds in coniferous forests
not suitable for orchid growth. Based on the available data it is seen that about 300
species of orchids are found here of which the genus Habenaria is the most dominant
followed by Bulbophyllum, Dendrobium, Eulophia, Eria, Herminium, Liparis, etc.
Genera like Archineottia, Coeloglossum, Hemipilia, etc. are confined to this region
only.
II- Peninsular Region: This region is comprised of Eastern and Western Ghats, Madhya
Pradesh, Andhra Pradesh, Gujurat, Gangetic plains, etc. Out of these the Western Ghats,
recognized as one of the 18-mega diversity Hot-Spot area of the world, with high rain-fall and
high humidity has dense moist and dry deciduous forests, tropical evergreen forests supporting
a highly diverse and rich flora having many endemic species. The warm humid climate coupled
with high degree of rain fall provided congenial conditions for the growth of orchids and more
than 390 species of orchids are reported from the Peninsular region. Herminium is reported to
be the largest genus in order of dominance and is followed by Oberonia, Dendrobium,
Bulbophyllum, Liparis, Eria, Eulophia, Peristylus, Luisea, etc. Genera like Aenhenrya,
Disperis, Diplocentrum, Sirhookera, Seidenfadeniella, Smithsonia, Taprobanea,
Xenikophyton, etc. are restricted only to this region.
III- Andaman & Nicobar Islands: It is a group of 319 islands and islets in the Bay of Bengal.
The climatic condition of these islands is mainly governed by the south- east monsoon. The
heavy mist, high rainfall and the surrounding sea keeps the island forests moist round the year
thus offering a favourable habitat for a luxuriant epiphytic flora including the orchids. So far
nearly 120 species belonging to about 53 genera have been recorded from this region. The
genus Dendrobium is the largest which is followed by Eulophia, Bulbophyllum, Luisea,
Peristylus, Eria, Aerides, Phalaenopsis, Malaxis, etc. Genera like Plocoglottis, Vrydagzynea,
Grosourdya are confined only to these islands.

Threatened species:
Species like Anoectochilus clarkei, Aphyllorchis gollani, Calanthe pachystalix, Coelogyne
treutleri, Chrysoglossum hallbergii, Dendrobium aurantiacum, Bulbophyllum acutiflorum,
Bulbophyllum aureum, Bulbophyllum elegantulum, Bulbophyllum nodosum, Dendrobium
tenuicaule, Habenaria flabelliformis, Liparis biloba, Malaxis crenulata, Neottia inayatii,
Oberonia angustifolia, Oberonia griffithiana, Oberonia clarkei, Oberonia anthropophora,
Oberonia lobulata, Oberonia platycaulon, Paphiopedilum wardii, Pleione lagenaria, Vanda
wightii, Zeuxine pulchra are considered as extinct.
Conservation Measures Factors responsible for depletion of orchids:
• Urbanization
• Loss of habitat- destruction of forests (epiphytic) and over grazing (terrestrial)
• Attractive flowers
• Exploitation as Medicinal plants
• Smuggling orchid species collected from the wild by the orchid traders
• Over enthusiastic collection by students and researchers • Natural calamities
• Non-availability of pollinators.
FIGURE00: DISTIBUTION OF ORCHIDS IN INDIA AT A GLANCE
Fig01: Ten dominant genera of orchids in India
Ref: Abraham, A. and P. Vatsala 1981. Introduction to Orchids. Tropical Botanic
Garden & Research Insititute. Trivandrum.
Bose, J.K. and S.K. Bhattacharjee 1980. Orchids of India. Calcutta.
Chowdhery, H.J. 1998. Orchid flora of Arunachal Pradesh. Bishen Singh Mahendra Pal
Singh, Dheradun.
Deva, S. and H.B. Naithani 1986. The Orchid Flora of North West Himalaya. Print &
Media Associate, New Delhi.
Dressler, R.L. 1993. Phylogeny and Classification of the Orchid family. Cambride
University Press, Cambridge.
Duthie, J.F. 1906. The Orchids of the north-western Himalaya. Ann.Roy. Bot. Gard.
Calcutta 9:81-211.
 Fischer, C.E.C. 1928. Orchidaceae in Gamble, J.S., Flora of Presidency of Madras 8:
1399-1478
Lindley, J. 1857. Contributions to the Orchidology of India1. J. Linn. Soc. 1: 170-190.
Lindley, J. 1859. Contributions to the Orchidology of India2. J. Linn. Soc.3: 1-63.
Nagano,Y. 1960. Orchids in Japan. 50-55. 1960. In Proc. 3rd World Orchid Conference,
London.
Nayar, M.P.1966. ‘Hot Spots’ of Endemic Plants of India Nepal and Bhutan. TBGRI,
Thiruvananthapuram.
Pradhan, U.C. 1976. Indian Orchids- Guide to identification and Culture. Volume-1
Kalimpong and Faridabad.
Pradhan, U.C. 1979. Indian Orchids- Guide to Identification and Culture. Volume-2.
Faridabad.
Raizada, M.B., H.B. Naithani and H.O. Sexana1981.Orchids of Mussoorie. Dheradun.
Santapau, H. and Z. Kapadia 1996. The orchids of Bombay. Delhi.
Sathish Kumar, C. and K.S. Manilal 1994. A Catalogue of Indian Orchids. Bishen Singh
Mahendra Pal Singh, Dehradun.
Seidenfaden, G. and C.M. Arora 1982. An enumeration of Orchids of North Western
Himalaya. Nord. J. Bot. 2: 7-27.
Singh, K. P., S. Phukan & P. Bujarbarua 2002. Orchidaceae. In Floristic Diversity &
Conservation Strategies in India. Vol. IV. Botanical Survey of India, Calcutta. pp. 1735-
1827

Remark- A good morphological study is required for conservation and study of orchids.
Investigations on morphological diversity could open avenues for identification of new and
enhances orchids for pot culture, herbal preparations and exhibits for market displays.

Fig02: Schematic diagram of an orchid flower.

Ref: https://www.researchgate.net/publication/221796068

Fig 03: Structure and diversity of orchid flowers.

Structure and diversity of orchid flowers.
(A) Sample of perianth diversity in Orchidaceae. Even though other families including
Zingiberaceae, Corsiaceae and Cannaceae have independently evolved structures termed lips,
the lip of orchids shows unprecedented morphological diversity. These examples represent the
wide degree of variation of the perianth in the five orchid subfamilies. From left to right, upper
row: Apostasia wallichii (subfamily Apostasioideae); Vanilla imperialis (subfamily
Vanilloideae); Phragmipedium caudatum (subfamily Cypripedioideae); Ophrys apifera; lower
row: Habenaria radiata (subfamily Orchidoideae); Aerangis fastuosa, Telipogon intis,
Cattleya tenebrosa, Psychopsis papilio (subfamily Epidendroideae).
(B) Graphic representation of a transverse section through the flower of an orchid
(Phalaenopsis hybrid) depicting the general arrangement of perianth organs, column, and ovary.
(C) Front view of an orchid flower (Phalaenopsis hybrid). The perianth is composed of six
organs that are arranged in two whorls and represent at least three classes of organ identity. In
the first (outer) floral whorl, there are three outer tepals (T1, T2 and T3; often also termed
‘sepals’), with T1 being a median and T2 and T3 being lateral outer tepals; in the second floral
whorl, there are two laterals inner tepals (t1 and t2; ‘petals’) and a median inner tepal (t3),
called lip or labellum.
(D) Schematic representation of organ identity in the orchid perianth. The three colours
symbolize different organ identities [outer tepals green, lateral inner tepals yellow, lip
(labellum) red] as possibly determined by a combinatorial code involving differential
expression of four clades of DEF-like, MIKC-type, MADS-box genes.
Ref. to figure 03: The Author 2009. Published by Oxford University Press on behalf of the
Annals of Botany Company.

Pollination of Orchids

Orchids, the largest and most diverse family of flowering plants, have evolved intricate and
often deceptive pollination strategies to ensure their reproductive success. Their remarkable
adaptations to attract and guide pollinators are a testament to the coevolutionary relationships
that shape the natural world.

Pollination Mechanisms

Orchid pollination is characterized by the transfer of pollen grains from the male anther to the
female stigma, typically mediated by animal pollinators. Unlike other flowers, orchid pollen is
packaged into sticky masses called pollinia (singular: pollinium), making them incapable of
wind dispersal. This necessitates the involvement of pollinators, such as bees, wasps, moths,
flies, beetles, and even some birds.

Pollinator Attraction and Deception

Orchids employ a variety of strategies to attract pollinators, often mimicking the appearance,
scent, or behavior of other organisms to deceive and manipulate their visitors. These deceptive
mechanisms include:

Mimicry: Many orchid species mimic the appearance of female insects, enticing male
pollinators attempting to mate with the flower. This pseudocopulation results in the transfer of
pollinia to the pollinator's body.

Pheromone Mimicry: Some orchids produce pheromones that resemble those of female insects,
further attracting male pollinators.

Nectar Rewards: While some orchids offer nectar rewards to their pollinators, others deceive
them with false nectar guides.

Visual Cues: Orchids often exhibit vibrant colors, patterns, and shapes to attract pollinators.

Fragrance: Orchids emit a wide range of fragrances, some mimicking the scent of attractive
mates or nectar sources, to guide pollinators.
Mechanical Traps: Some orchids, such as hammer orchids, use mechanical traps to capture and
guide pollinators onto the stigma.

Pollinator Specificity

Orchids often exhibit remarkable specificity in their choice of pollinators, relying on specific
adaptations to ensure effective pollen transfer. For instance, the long nectar spurs of
Madagascar's star orchids (Angraecum sesquipedale) can only be reached by the proboscis of
the Xanthopan morganii hawkmoth.

References

1. Dafni. (1984). Pollination and seed dispersal in orchids. In The biology of orchids
(pp. 251-346). Springer, Dordrecht.
2. K. J. Willis, & J. C. Keeling. (2009). Pollination ecology of orchids. In The orchids
(pp. 107-132). Cambridge University Press.
3. J. D. Ackerman. (2011). Orchid pollination: Biology, evolution, and conservation.
Princeton University Press.
4. M. A. Renner, & L. Schlüter. (2004). The reproductive biology of orchids. In The
chemistry and biology of the Orchidaceae (pp. 77-119). Springer, Berlin,
Heidelberg.
5. D. W. Inouye. (1980). The effect of pollinator activity on fruit set and seed
production in four species of wild blueberry. Oecologia, 46(3), 349-354
Pollinator Type Example Family Characteristics
Insect Bees Apidae family Bees are highly
effective pollinators
of orchids due to
their hairy bodies,
which effectively
transfer pollinia.
They are attracted to
orchid flowers by
their vibrant colors,
sweet scents, and
nectar rewards.
Insect Wasps Vespidae, Wasps, particularly
Crabronidae, and orchid wasps, have
Sphecidae families evolved specialized
relationships with
specific orchid
species. They are
attracted to orchids
by their deceptive
mimicry of female
insects.
Insect Moths Noctuoidea, Moths are important
Bombycoidea, and pollinators of night-
Geometroidea flowering orchids,
superfamilies guided by the
flowers' strong
fragrances and
visual cues.
Insect Flies Muscidae, Flies, particularly
Calliphoridae, and carrion flies and fruit
Drosophilidae flies, are attracted to
families orchids with foul-
smelling odors,
often mimicking
rotting flesh or fruit.
Insect Beetles Scarabaeidae, Beetles are attracted
Cerambycidae, and to orchids with
Curculionidae nectar rewards or
families pollen-rich flowers.
Some beetles, such
as long-horned
beetles, have
specialized
mouthparts adapted
for pollination.
 Non – insect Hummingbirds Trochilidae family Hummingbirds are
attracted to orchids
with brightly
colored, tubular
flowers that provide
nectar rewards.
Their long, slender
bills are perfectly
adapted for reaching
nectar deep within
orchid flowers.
Non – insect Bats Pteropodidae and Bats are important
Phyllostomidae pollinators of night-
families flowering orchids,
guided by the
flowers' strong
fragrances and bat-
specific floral cues.
Non – insect Snails Helicidae and Snails, particularly
Zonitidae families land snails, are
attracted to orchids
with sticky pollinia
that adhere to their
bodies as they crawl
through the flowers.

Table - Insect pollinators and non-insect pollinators of orchids

References

1. Ackerman, J. D. (2011). Orchid pollination: Biology, evolution, and conservation.

Princeton University Press.
2. Dafni, A. (1984). Pollination and seed dispersal in orchids. In The biology of orchids
(pp. 251-346). Springer, Dordrecht.
3. Willis, K. J., & Keeling, J. C. (2009). Pollination ecology of orchids. In The orchids
(pp. 107-132). Cambridge University Press.
4. Renner, M. A., & Schlüter. (2004). The reproductive biology of orchids. In The
chemistry and biology of the Orchidaceae (pp. 77-119). Springer, Berlin, Heidelberg.
5. Inouye, D. W. (1980). The effect of pollinator activity on fruit set and seed production
in four species of wild blueberry. Oecologia, 46(3), 349-354.
Insect pollinators of India
Introduction
ORCHIDACEAE IS one of the highly evolved families of flowering plants in the world. It
comprises about 25,000 to 35,000 species; inhabited everywhere except the poles (Dressler,
1981). The flowers of this family have a unique trait where the male part of the flower
comprises only one stamen and is fused with female parts of the flowers to form a structure
called column. Pollens lay at distal end of the column as discrete masses (pollinia). Pollinia
attach with stipe or caudicle to a sticky viscidium to form a pollinarium. This pollinarium sticks
to the body of pollinator and precisely delivered on to the stigma so as to effect crosspollination.
Pollinators play a significant role in evolving new novel forms and in maintaining orchid
species diversity (Buragohain and Chaturvedi, 2016; Chaturvedi, 2010a, 2011; Xu et al., 2012).

Orchid Pollinators
The flowers of orchids are pollinated by various vertebrate and invertebrate taxa. Their
pollinators range from insects, birds, and rodents. However, Hymenoptera (bees and wasps)
are common pollinators of orchids. Pollination rewards include nectar (insects and birds), floral
fragrance (male euglossine bees), resins (used by bees for nest building), and oils (used by
anthropoid bees to feed larvae). Deceptive pollination also occurs in orchids (Buragohain and
Chaturvedi, 2016; Fantinato et al., 2017; Thalwitzer et al., 2018). Orchids deceive pollinators
in several ways like sexual deception, food or brood site deception, nectar deceit, and oil deceit.
In flowers of Ophrys apifera, the lip of the flowers is structured in such a way that it looks like
a female of the pollinating insect (Eucera spp.). While the male insect tries to copulate with the
deceptive flower labellum, the pollina gets attached to its body. The insects make similar
attempts with other flowers and pollinia get deposited on the stigma of different flowers.
Pollination by this mechanism is also referred to as pseudocopulation. Some orchid species are
pollinated by various pollinators, but some are very specific and are pollinated by particular
pollinators. The specialization reduces wastage of pollinia and allows transferring the pollinia
to the specific flowers. The specialty is favoured by body size of insect, flower morphology,
and the position of pollen attachment on pollinator’s body. The highest numbers of orchids are
pollinated by bees followed by wasps, flies, birds, setting moths, hawkmoths, butterflies, and
beetles.

Bee-Pollinated Orchids
Bees or wasps pollinate about 60% of the orchids. These flowers have well-developed landing
platform and have nectar glands or marks of contrasting colour pointing the way to nectar. The
nectar may be present in minimal quantity and more or less concealed. Bee-pollinated flowers
emit a fresh and sweet odour and are usually horizontally placed (D'Auria et al., 2019). The
flowers are typically coloured with violet, blue, green, and yellow. Some species of orchids
produce pseudopollen which is used as a substitute reward by pollinating bees. Bees also collect
an award from orchids as oil, food, and resin for nest building. Euglossine bees collect scent
compounds for the use of courtship display. The flower morphology also deceives bees. The
two non-rewarding species of orchids, Dendrobium infundibulum and Cymbidium insigne
mimic in flower morphology of Rhododendron lyi, a nectar-rewarding species. The flowering
season of these species overlaps and hence, get pollinated by Bombus eximius (Kjellsson et
al., 1985). Some species of Eria (Eria monostachya and E. paniculata) and Maxillaria (Beck,
1914) and most of the species in genus Polystachya show mimicry in the production of
pseudopollen. Some orchids use both physical appearance and chemical cues to deceive the
pollinators. The flowers of Drakaea spp. are similar to the female wasp in the genus
Zaspilothymus; it also releases a chemical that mimics a mating pheromone of this female
wasp. The pollens get transferred in the process of mating with deceptive flowers. Orchids also
use traps, triggers or false nectar rewards to attract pollinators. Rhynchostylis retusa is
pollinated by Xylocopa violacea and X. aestuans (Buragohain et al., 2015), Phaius
tankervilleae is pollinated by X. violacea (Buragohain et al., 2016), and Cymbidium pendulum
by Apis mellifera (Attri and Kant, 2011).
Moth-Pollinated Orchids
For pollination, moths either land on the flowers or hover in front of the orchid flower. The
flowers usually open during the night. The flowers are placed either horizontally or hanging;
the colour of flower ranges from white to green. Long-tongued moths pollinate the long spur
flowers whereas short tongue moths pollinate species bearing moderate spur flowers. They
produce abundant nectar placed down below the spurs. Some orchids have a very specialised
relationship with the pollinators. Darwin’s orchid (Angraecum sesquipedale) and Ghost orchid
(Dendrophylax lindenii) require specific Lepidopteran pollinator whose proboscis can reach
long nectar spur.
Butterfly-Pollinated Orchids
Butterfly-pollinated orchids are bright in colours e.g. red, orange, blue or yellow, and bear
sweet fragrance. Such flowers may or may not have a nectar gland. Sometimes nectar is
concealed deep below in the spurs. In India, Habenaria foliosa var. foetida is pollinated by blue
tiger butterfly (Tirumala limniace) during day time and by moth of the genus Dysgonia during
the night. The fetid odour during day time attracts butterfly offering it with nectar whereas
during the night, the moths are attracted by whitish green colour and for nectar (Dangat and
Gurav, 2014). Orchids also attract pollinators by releasing compounds that are exacting to sex
pheromones or sometimes secrete a chemical that is collected by pollinator for defence or
mating attraction. Epidendron paniculatum releases pyrrolizidine alkaloids (PAs) which is used
by lepidopterans and nymphalid butterfly as mating attraction and also for protection. In China,
Ludisia discolor and Calanthe argenteostriata are pollinated by butterflies (Zhang et al., 2010).
Fly-Pollinated Orchids
Orchids are pollinated by flies belonging to different families. The colour of the flies varies
from yellow to brown. The flowers of fly fertilized species are horizontally placed, fringed and
some have landing platform. Nectar may be present or absent, if available it is superficially
accessible. The flowers may open during day or night and emit sweet to an unpleasant odour.
Kumar and Rawat (2011) reported that Epipactis veratrifolia is pollinated by hoverfly (Ischidon
scutellaris) while it rests in its flowers for laying the eggs.
Bird-Pollinated Orchids
Some orchids have also been reported to be pollinated by humming birds. The flowers of
humming birdpollinated orchids are tubular, placed horizontally, hanging, and brightly
coloured. In China, Coelogyne rigida is pollinated by birds (Wang et al., 2008).
Rodent-Pollinated Orchids
In China, Cymbidium serratum is pollinated by rodents. The wild mountain mice prefers to eat
brightly coloured succulent lips of C. serratum because the lips are sweet, whereas lateral petals
and sepals are slightly bitter in taste. The body length of the pollinator matches with the flowers
height enabling the pollinator to obtain the flowers. The production of odour also synchronises
with mouse activity (Wang et al., 2008). It was the first report showing that orchids may also
get pollinated by rodents.
Beetle-Pollinated Orchids The beetle pollinated orchids possess readily available nectar,
produces fruity smell or distinct odour. Flowers are opened during day or night. The
beetlepollinated flowers are dull white, green to dark brown, and purple to bright yellow. In
China, Holcoglossum rupestre is the only orchid pollinated by beetles (Jin et al., 2005).
Auto-pollination in Orchids
In autopllinated species, the pollinia are located just above the stigma and get fertilised in the
absence of pollinators. The process may occur due to the presence of powdery pollinia and
deformation of part of the column. The autopollination is most common where the pollinators
are rare. The anthers of Holcoglossum amesianum oppose the direction of gravity by 360° and
pollens get inserted into its stigma cavity (Liu et al., 2006). In Paphiopedilum parishii, the
anther is liquidated and droped onto the stigmatic surface (Chen et al., 2012). In Epipogium
roseum, rostellum degenerates and looses its function and enables the contact between
stigmatic secretions and pollinia at the time of bud development (Zhou et al., 2012).
Autopollination is considered as possible adaptation mechanism of orchids in insect-scarce
habitats (Chen et al., 2012; Liu et al., 2006).

References
1. Attri, L. K. and R. Kant. 2011. Orchid Pollination: An observation on pollination-
pollinator interaction in Cymbidium pendulum (Sw.) Roxb. Curr. Bot., 2(7): 05-08.
2. Beck, G. 1914. Die Pollennachahmung in den Bluten der Orchideen-Gattung Eria
Sitzungsberichte. Akademie der Wissenschaften in Wien, 123: 1033-46.
3. Buragohain, B. and S. K. Chaturvedi. 2016. Deceptive pollination in an endangered
orchid Vanda coerulea Griff. ex Lindl. (Orchidaceae). J. Orchid Soc. India, 30: 31-35.
4. Buragohain, B. S. K. Chaturvedi, and N. Puro. 2015. Biotic pollination in
Rhynchostylis retusa (L.) Bl. (Orchidaceae). Inter. J. Plant Rep. Biol., 7(1): 78-83.
5. Buragohain, B. S. K. Chaturvedi, and N. Puro. 2016. Biotic pollination biology of
Phaius tankervilleae (Banks ex L’ Herit) Bl. (Orchidaceae). Inter. J. Plant Rep. Biol.,
8(1): 75-81.
6. Chaturvedi, S. K. 2010a. Biotic pollination in Aerides odorata Lour. (Orchidaceae). Int.
J. Plant Rep. Biol., 1(2): 45-49.
7. Chaturvedi, S. K. 2010b. Orchids pollination: An overview. In: Proceedings National
Conference on Orchids: Systematics and Diversity Analysis for Conservation and
Sustainable Utilization (eds. S. P. Vij and Promila Pathak) pp. 17-24. The Orchid
Society of India, Panjab University, Chandigarh.
8. Chaturvedi, S. K. 2011. Anthoecology of pollination in orchids. Bioherald, 1(1): 13-26.
9. Chen, L. J., K. W. Liu, X. J. Xiao, W. C. Tsai, Y. Y. Hsiao, J. Huang, and Z. J. Liu. 2012.
The anther steps onto the stigma for self-fertilization in a slipper orchid. PLoS ONE, 7:
1-6.
10. D'Auria, M., R. Lorenz, M. Mecca, R. Racioppi, and V. A. Romano. 2019. Aroma
components of Cephalanthera orchids. Nat. Prod. Res., 29: 1-4.
11. Dangat, T. D. and R. V. Gurav. 2014. Pollination in Habenaria foliosa var. foetida
(Orchidaceae). Richardiana, 14: 219- 28.
12. Darwin, C. 1862. On the Various Contrivances by Which British and Foreign Orchids
are Fertilized by Insects, and on the Good Effect of Intercrossing. John Murray, London,
U.K.
13. Dodson, C. H. 1966. Orchid Flowers: Their Pollination and Evolution. Fairchild
Tropical Garden and University of Miami Press, Coral Gables, Florida, U.S.A.
14. Dressler, R. L. 1981. The Orchids: Natural History and Classification. Harvard
University Press, Massachusetts, U.S.A.
15. Fantinato, E., S. D. Vecchio, M. Baltieri, B. Fabris, and G. Buffa. 2017. Are food-
deceptive orchid species really functionally specialized for pollinators. Ecol. Res., 32:
951-59.
16. Jin, X. H., S. C. Chen, and H. N. Qin. 2005. Pollination system of Holcoglossum
rupestre (Orchidaceae): A special and unstable system. Plant Syst. Evol., 254: 31-38.
17. Kumar, P. and G. S. Rawat. 2011. Nature Precedings: hdl:10101/ npre.2011.6295.1.
18. Kjellsson, G., F. N. Rasmussen, and D. Dupuy. 1985. Pollination of Dendrobium
infundibulum, Cymbidium insigne (Orchidaceae) and Rhododendron lyi (Ericaceae) by
Bombus eximius (Apidae) in Thailand: A possible case of floral mimicry. J. Trop. Ecol.,
1: 289-302.
19. Liu, K. W., Z. J. Liu, L. Q. Huang, L. Q. Li, L. J. Chen, and G. D. Tang. 2006.
Pollination: Self-fertilization strategy in an orchid. Nature, 441: 945-46.
20. Thalwitzer, L., D. Kelly, R. D. Smissen, R. Butler, D. M. Suckling, and A. El-Sayed.
2018. Species-specific male pollinators found for three native New Zealand greenhood
orchids (Pterostylis spp.) suggest pollination by sexual deception. Aust. J. Bot., 66: 243-
54.
Success of Orchids in Adopting Different Special Pollination
Method
Orchid pollination methods by reward
Nectar
Orchid pollen is not used by honeybees as a source of food– instead they are attracted
mainly by the plant’s nectar.
Those orchids that have most clearly developed this adaptation have a spur at the base
of their lip. This means that the insect must have an appendage in order to reach the
nectar. When it does so, it brushes against the pollinia, masses of orchid pollen.
The most striking example is Angraecum sesquipedale, which drew Darwin’s attention.
Heeven predicted that a moth would be found with a proboscis long enough to reach
the nectar at the end of the spur. In fact, an insect exactly matching Darwin’s
description was found many years later. This type of pollination is o en described as
“lock and key,” because the insect’s organ fits into the flower just as a key fits into a
lock.
Trap strategy
In the case of slipper orchids (Cypripedium, Paphiopedilum), an insect in search of
nectar slips in under the column and leaves only once it has made its way along the side
of the gynoecium, carrying with it pollinia stuck to its back. This step prevents it from
pollinating the same flower. When it visits another flower, it will deposit the pollinia on
the stigmas before leaving, taking a new load with it. This is called “trap” pollination.
The insect-orchid association is so closely established in many orchids that it can be
described as “faithful” or “restrictive,” since only the type of insect capable of
pollinating a particular orchid effectively will be able to visit the flower and obtain its
nectar reward.
In addition, only orchids have this adaptation whereby pollen is clustered in pollinia,
small hard masses easily “carried” on an insect’s back or a bird’s beak, especially when
they have an adhesive disk (the viscidium).
Simulated pollen as a means of deception
Some orchids instead have a sort of pseudo-pollen, similar in consistency to pollen that
is edible for their pollinators. The insects, usually bees, then pick up and eat the
substance. Dressler also noted the presence of wax on the callus of the labellum of some
Maxillaria species that could be used by some bees to build their nests.
In other cases, orchids appear to promise nectar, but don’t actually produce any. Some
species, including Calypso, found in our peat bogs, have a plume of yellow hairs
resembling edible pollen at the tip of their false anthers.
Moveable parts
Plants with moveable parts are always fascinating– just think of the active traps on
insect-eating plants. Although the motion is mostly passive on orchids, the way that
some flower parts move to facilitate pollination is very interesting.
The labellum on various orchids lowers when a pollinator lands on it, making it easier
for pollinia to be deposited or collected. Some Pleurothallis species have hairs or
appendages that quiver in the wind, making them especially attractive to flies. The
Porroglossum and a few other genera have a hinged labellum that drops down toward
the gynostemma as soon as there is any pressure on the base of the gynostemma that
supports it. The only way out for the insect is to push past the stigma and the rostellum,
where it deposits some pollinia and picks up more. A er a few minutes, the labellum
returns to its initial position, ready for its next “victim.”
The ejection of the pollinia of the Catasetum is impressive: it is triggered as soon as
something (e.g. the tip of a pencil) touches a seta near the sticky viscidium—a substance
that requires vigorous effort to remove, such as rubbing the stigma of another flower
and thus leaving the pollinia behind.
Mimicry and other methods of pollination of orchids by signals
Mimicry
This is probably one of the most fascinating phenomena in the plant world, especially
because it manifests itself in such a wide variety of ways among different groups of
unrelated insects and orchids. Bulbophyllum orchids attract flies by resembling rotting
meat.
Many species mimic the flowers of other plants in order to attract their pollinators.
Dodson mentions a male bee that pollinates the Oncidium genus by attacking the
inflorescence that mimics another male in flight. The attacking bee’s head gets covered
in the ejected pollinia, which it then deposits on the next plant it “attacks”.
Pseudocopulation
Some flowers lure males by mimicking a female insect, in whole or in part. The
Trichoceros genus is an excellent example of this adaptation– its hairs and moveable
parts resemble a female fly. As Dressler reminds us, orchids are not equipped with
intelligence. This phenomenon, like those that depend on cross-pollination, is the result
of evolution: trial and error through genetic selection over the very long term and the
reproduction of successful individuals.
Colors and shapes
The flower colors we perceive are entirely different from those perceived by insects and
birds. They are just as important as the plant’s moving parts or the type of trap it uses.
Blue, violet, purple, yellow and white are most attractive to bees, whereas birds are more
drawn to contrasting colors, bright red in particular.
The shape of the markings on the labellum may also play a role in mimicry or as a
reward signal. The shape of the flower itself or of some of its parts also plays a key role,
not only in mimicry or pseudocopulation, but also in making the pollinator-flower
interaction as effective as possible. Insects o en require a “landing pad,” while tubular
flowers allow birds to hover in place while using their beaks to get at the nectar.
Scents
Just like colors, scents– both pleasant and rotten ones– influence the type of pollinator
associated with a particular plant. For instance, a Bulbophyllum inflorescence gives off
a putrefied scent to attract pollinating flies that are attracted to rotten meat.
Orchids’ success as one of the most evolved plant groups, their diversity and their broad
distribution around the globe all owe much to their highly diversified and sophisticated
means of pollination.
In addition to boasting the most popular cultivated species with showy blooms, the
Orchidaceae family includes many delightful members with flowers of unsuspected
complexity. Orchids offer much to interest amateur botanists, with their adaptations to
their habitats and their pollinators.
Reference :
1. Abel GJ. 2013. Migest: methods for the indirect estimation of bilateral migration.
Available at: https://cran.r-project.org/web/packages/migest/index.html
2. Balducci MG, van der Niet T, Johnson SD. 2020. Diel scent and nectar rhythms of
an African orchid in relation to bimodal activity patterns of hawkmoth
pollinators. Annals of Botany 126: 1155–1164.
3. Cozzolino S, Scopece G, Roma L, Schlüter PM. 2020. Different filtering strategies
of genotyping-by-sequencing data provide complementary resolutions of species
boundaries and relationships in a clade of sexually deceptive orchids. Journal of
Systematics and Evolution 58: 133–144.
4. Darwin C. 1859. On the origin of species by means of natural selection or the
preservation of favored races in the struggle for life. London: John Murray.
5. Johnson SD, Schiestl FP. 2016. Floral mimicry. Oxford: Oxford University Press.
6. Phillips RD, Reiter N, Peakall R. 2020a. Orchid conservation: from theory to
practice. Annals of Botany 126: 345–362