Conservation and Reintroduction of the Native Orchids of Singapore

2005·1 MB·

by  Yam, Tim Wing

Selbyana 26(1,2): 75-80. 2005.
CONSERVATION AND REINTRODUCTION OF THE NATIVE ORCHIDS
OF SINGAPORE
TIM WING Y AM* AND AUNG THAME
Singapore Botanic Gardens, 1 Cluny Road, Singapore 259569 Singapore.
Email: [email protected]
ABSTRACT. Some 221 species of native orchids have been recorded in Singapore. Of these, however, ca.
170 orchid species are considered to be extinct, and only four are viewed as common. The orchid conser
vation program at the Singapore Botanic Gardens aims to monitor these species, to explore ways to conserve
their germplasm, and to increase their number for subsequent reintroduction into appropriate habitats,
including managed parks and roadsides. Thus far, we have successfully reintroduced Grammatophyllum
speciosum, Bulbophyllum vaginatum, and Bulbophyllum membranaceum. Recently, we initiated the Orchid
Cryo-Seed Bank Project, and have managed to successfully store seeds of four native species. They are
Dendrobium crumenatum, Spathoglottis plicata, Bulbophyllum vaginatum, and Dendrobium anosmun.
Key words: conservation, reintroduction, seed bank, Singapore, native, orchids
INTRODUCTION METHODS: HABITS AND HABITATS
Native orchids in Singapore can be divided by
Singapore is located at ca. 1° north of the
plant habit into two main groups: epiphytes and
equator, off the southern tip of the Malay Pen
terrestrials. They also can be grouped according
insula between the South China Sea and the In
to habitat, including open areas, semi-shade, and
dian Ocean. The nation consists of the main is
low-sunlight forest floors.
land of Singapore and 58 nearby islands. The
total land area is ca. 690 km2• The whole island
Epiphytes
consists of mostly lowland. The highest point is
at Bukit Timah, which reaches an elevation of No other genus better illustrates the epiphytic
165 m. The equatorial climate has a relatively orchids of Singapore than the Dendrobium spe
uniform temperature and high humidity. A ver cies, almost all of which are epiphytes. The larg
age daily temperatures fluctuate between 25.2°C est genus among the native orchids, Dendrobium
and 32°C. Annual rainfall is ca. 1700 mm, with consists of 38 species (Tan 1984) or more than
the wettest months November-January. 20% of the total number of orchids in Singapore.
Singapore is a modem city, yet it has many
Dendrobium crumenatum. The pigeon orchid
interesting types of natural habitats. The heart of
(D. crumenatum) is a well-known native
the main island has a primary rain forest and a
species that can commonly be seen growing
freshwater swamp forest. In addition, some man
on the trunk of roadside trees. It is a delight
groves remain along the coast. Other habitats
to find them in bloom, as the flowers are
consist of secondary forests, shrub, grasslands,
sweetly scented. The species flowers 9-10
and urban parks and fields.
days after a heavy rainstorm. Similar flow
Of the 221 species of native orchids recorded
ering patterns have been observed in some
in Singapore (Keng et al. 1998), more than 90%
native Bulbophyllum, Thrixspermum, Brom
are endangered, vulnerable, rare, or extinct. This
headia, and Taeniophyllum species.
estimate is based on lists in a preliminary report
Dendrobium leonis section Aporum. Another
on the conservation status of plants native to
interesting but rare native orchid, D. leon is,
Singapore (Ng & Wee 1994, Tan 1995). The has leaves that are laterally flattened, thick
Singapore Botanic Gardens, therefore, has initi
and fleshy, and alternate in two rows. In
ated an orchid conservation program to monitor dividual yellowish-green flowers are borne
these species, to attempt to find ways and means near the apex of the stems. The flowers are
to conserve their germplasm, and to increase only 1.5 cm across and have an extremely
their number for subsequent reintroduction into sweet vanilla-like fragrance that can be de
appropriate habitats in nature reserves, parks, tected from a distance of 5 m.
and roadside trees. Dendrobium aloifolium section Aporum. The
native orchid D. aloifolium bears flowers 4
mm in diameter, probably the smallest in
* Corresponding author. the section.
75
76 SELBYANA Volume 26(1,2) 2005
Dendrobium grande section Aporum. The na lip, white with a pale yellow tip, is hairy in
tive orchid D. grande has yellowish-green the middle.
flowers, ca. 9 mm wide, tinted with red near Cymbidium finlaysonianum. The most com
the base of the sepals and petals, and the mon of the three Cymbidium species in Sin
lip is deeply cleft ed. gapore is C. finlaysonianum. Other species
Dendrobium anosmum (syn. Dendrobium su are C. bieolor var. pubescens and C. aloi
perbum). Although widespread in Southeast folium. All native Cymbidium species are
Asia, this orchid species can no longer be epiphytes.
found in Singapore. Dendrobium anosmum Coelogyne pandurata. Among the four native
produces 1-4 large fragrant flowers at each species of the genus Coelogyne, C. pandur
node on leafless pendent stems. The flowers ata is the most outstanding. The flower is
range in color from dark rose to deep lav ca. 6.5 cm across. Its petals and sepals have
ender. The hairy lip is usually marked with an attractive, clear apple-green color. The
deep purple stripes in the throat. protruding lip has some conspicuous dark
Bulbophyllum vaginatum section Cirrhopetal brown/red, almost black markings, hence,
um. The second largest orchid genus in Sin its common name, the black orchid.
gapore is Bulbophyllum. Species of this ge Thrixspermum amplexicaule. Several species
nus are divided into many sections. Of the of the genus Thrixspermum, which is most
28 recorded species (Tan 1984), B. vagina ly epiphytic, have been recorded in Singa
tum is one of the most unusual. It grows in pore. Thrixspermum amplexicaule (syn. T.
fairly exposed areas. Some plants grow nat lilacinum) is the most attractive, with a pale
urally on branches of rain trees (Samanea lilac-colored flower ca. 3 cm in diameter.
saman) and on Eugenia grandis in the Sin The plant was first found in a semi-aquatic
gapore Botanic Gardens. The plants usually habitat in Singapore.
cover an extensive area of a branch and pro Thrixspermum trichogiottis. Also found in
duce a spectacular sight when in full bloom. natural areas in Singapore, T. trichoglottis
The flowers are creamy-yellow with ca. 15 is very small with long seed capsules. The
of them arranged in a fan shape whorl or in flowers are creamy yellow, with a brown
a circle at the tip of the scape. spot on the lip. Among the other species of
Bulbophyllum medusae. One of a number of this genus are T. calceolus, T. notabile, and
interesting Bulbophyllum species in Singa T. ridleyanum.
pore, B. medusae, another native orchid, re Grammatophyllum speciosum. Although Sin
sembles B. vaginatum but has paler and lon gapore is a small country, it is the home of
ger lateral sepals (12 cm). the largest orchid plant in the world, G. spe
Bulbophyllum membranaceum. In the Buk:it ciosum. Also known as the tiger orchid, be
Timah Nature Reserve, a clump of B. mem cause of the markings on the flowers that
branaceum is found creeping on a large resemble the skin of a tiger, it is extremely
piece of granite. Among the smallest native rare if not already extinct in the wild in Sin
orchids, it has very small flowers ca. 6 mm gapore. Grammatophyllum speciosum was
long that do not open completely; the upper last found in the wild in Tuas and Pulau
sepal is pale yellow, whereas lateral sepals Ubin (Ridley 1900). Since a mature plant
are dark red, and the petals, 1.5 mm long, could weigh more than a ton, it is a wonder
appear translucent. Other interesting Bul that such a huge plant could live on the
bophyllum of Singapore are B. purpures trunk of a tree.
cens, B. lepidum, and B. blumei. Taeniophyllum obtusum. The extraordinary
Vanilla griffithii. The Vanilla genus, among the genus Taeniophyllum, the "leafless" orchid,
most widely distributed in the world, has ca. has stems greatly reduced in size and cov
100 species distributed throughout the trop ered by scale-like leaves. Roots are fleshy
ics, from Central and South America, across and spread over the bark of the host tree,
Central Africa, Southern India, Sri Lanka, usually on top of a thin layer of moss. These
and all of Southeast Asia to the Pacific Is green roots replace leaves as the photosyn
lands. In Singapore, the genus is represent thetic organ. As the plant is almost flat and
ed by V. griffith ii, a relatively common epi its color blends very well with its host, one
phytic climber found in the Upper Pierce can hardly spot them in the wild. Taenio
Reservoir, Nee Soon, and the Mandai For phyllum obtusum can be found near
est. The plant climbs on tree trunks in a swampy areas in Singapore. The roots of
zigzag fashion. Petals and sepals of the the plant are ca. 2-3 mm wide. Flowering
flower are white, flushed with pale green, is gregarious, with the flower 5 mm wide;
2.5-3 cm long and 1.4-1.5 cm wide. The petals and sepals are orange-yellow, and the
SECOND IOCC PROCEEDINGS 77
lip is fleshy and concave, and white in color. Nephelaphyllum pulchrum. Among the group
Flowers only last for one day. Some of the of native orchids that dwell on the forest
Taeniophylium species are known to pro floor in Singapore, N. pulchrum thrives
duce a sweet fragrance that attracts polli where the light intensity usually does not
nators. exceed 3000 lux during most of the day.
Only occasionally do sunrays manage to
Other beautiful native epiphytes include Po
penetrate the canopy to reach the forest
matocalpa latifolia, Arachnis hookeriana, Rhyn
floor. This native orchid has very interesting
chostylis gigantea, Renanthera histrionica, Pha
and showy leaves and delicate flowers. The
laenopsis cornu-cervi, Liparis elegan~, Liparis
leaves are fleshy; they are mottled light and
hyacinthoides, Eria javanica, Eria pudica, Eria
dark green and flushed with purple. The
pulchella, Dipodium pictum, Ariopsis javanica,
flowers tend to crowd together on the short
and Flickingeria comata. Some of these are ex
spike. The pinkish sepals and petals that all
tremely rare if not extinct in Singapore.
curve downwards are ca. 1.3 cm long.
Calanthe pulchra. Another forest-floor dweller,
Terrestrials C. pulchra has striking orange flowers that
do not open completely. The flowers are
Of the total number of native orchid species
densely crowded along the 50-60 cm long
in Singapore, ca. 25% are terrestrials. These spe
inflorescence. A distinguishing feature of
cies can be found either in open areas or dwell
the flower is that its spur curves up like a
ing in the shade on forest floors.
hook. The leaves can reach a length of 70
Spathoglottis plicata. One of the most common cm and a width of lO cm.
terrestrial orchids in Singapore, S. plicata, Plocoglottis javanica. Quite a common terres
frequently is found in open areas of the Bu trial orchid in Singapore, this inconspicuous
kit Timah Nature Reserve and the Central forest-floor dweller has long pseudobulbs,
Catchment. It usually grows among grasses which bear a single leaf. The leaves are 35
and ferns. The local species has two varie cm long by lO-12 cm wide. The long flow
ties: the dark pink and the alba forms. er spike carries some yellow flowers that
Spathoglottis plicata is very free flowering are spotted with red.
and has been used for landscaping. Cystorchis variegata. Unlike Plocoglottis ja
Arundina graminifolia. Another common ter vanica, C. variegata is a very rare species.
restrial species is A. gramin(folia. Often This native forest-floor dweller has very at
found growing in habitats similar to those tractive foliage. The leaves are arranged to
of Spathoglottis plicata, A. graminifolia is wards the apical part of the rhizome. They
very free flowering in the lowland tropics. are light green in color with a darker net
The vegetative parts of A. gramin!folia re work of venations. The half-opened flowers
semble bamboo, which accounts for its are borne on the elongated flower spike; the
common name, the bamboo orchid. sepals are brown with a tinge of pink while
Bromheadia finlaysoniana. Among the native the petals are white.
orchid species that prefer semi-shade, the Claderia viridiftora. Also found on the forest
familiar B. finlaysoniana is usually found floor of Singapore, C. viridiflora has a flow
along roadsides or on hill slopes. Like Den er spike that bears a succession of many
drobium crumenatum, B. finlaysoniana flowers, one or two at a time. The flowers
flowers a few days after a rainfall. The are greenish, sepals and petals are ca. 2.5
flower is very attractive, faintly scented, cm long.
white, with a yellow patch on the lip. Un Zeuxine clandestine. Among the less-known
fortunately, the flowers only last for a few orchids found in Singapore is Z. clandes
hours. tine. Quite a large population of the species
Eulophia graminea. One of two species of the has been found in Bukit Timah, growing on
genus Eulophia found in Singapore, E. gra the floor of a secondary forest. The plant is
minea is a very hardy plant. It grows among an inconspicuous creeper, with a fleshy rhi
grasses and in partially shaded hill slopes zome. A young plant lies rather close to the
and wastelands. ground, just like grass. When it begins to
Eulophia squalida. Found in the Bukit Timah bloom, a flower spike of ca. 10-20 cm pro
Nature Reserve growing on a rather steep trudes from the ground, bearing many small
slope, E. squalida has a flower with an un flowers. The flowers are light green in color
usual color. The sepals are brownish-olive and hardly open. The sepals are hairy, and
and the petals white. The lip is pale mauve ca. 3 mm long. The lip is a little shorter than
and has a white central area. the sepals.
78 SELBYANA Volume 26(1,2) 2005
Didymoplexis pallens. This species is an ex Choa Chu Kang, Jurong, Ang Mo Kio, and Ser
ample of another group of terrestrial orchids angoon, where native orchids used to thrive, no
that dwell on the forest floor but are my longer exist. Thus an orchid conservation pro
cotrophic (Arditti 1992). These orchids are gram was initiated to monitor these species and
parasitic on the fungi that associate with to attempt to find ways and means to conserve
them. All orchids rely on mycorrhizae for their germplasm and to increase their numbers
their early growth, but the mycotrophic or for subsequent reintroduction into appropriate
chids depend on the fungus to provide them habitats in the nature reserves, parks, and road
with nutrients throughout their life. These side trees. The strategies being explored by the
species usually dwell on the forest floor un Singapore Botanic Gardens are (1) propagation
der dense canopy, in areas where little light and reintroduction, and (2) cryo-seed banks.
can reach. Didymoplexis pallens, found in
Bukit Timah Nature Reserve, has a fleshy Conservation and Reintroductiou
underground rhizome; the flower spike is
soft and slender, bearing several flowers. First, we want to propagate species vegeta
The flowers are pale brown-olive, with a tively and by in-vitro culture. To increase the
tinge of pink, ca. 1.4 cm long. The dorsal population of some of the rarer species, which
sepal fuses to the petals for half its length; will be either selfed or sibbed, seeds are ger
lateral sepals are also joined to the petals minated in vitro (Yam & Weatherhead 1988),
towards the base. The lip is light yellow, ca. and seedlings are introduced back to nature. So
5 mm long. The species is not easily seen, far, we have managed to propagate a number of
because it has no visible vegetative part ex orchid species and have reintroduced three spe
cept for the erect flower spike, which hardly cies to nature areas in Singapore: Grammato
can be noticed in its natural habitat. If a phyllum speciosum, the tiger orchid; Bulbophyl
flower is pollinated, however, the seed cap lum vaginatum; and B. membranaceum.
sule can be seen in the wild. Owing to the H.N. Ridley, an early director of the Singa
difficulties in locating the plant, very little pore Botanic Gardens, recorded that the tiger or
is known about this orchid. Last year, we chid was found in the wild in Toas (Tuas) and
also discovered another mycotropic orchid, Pulau Ubin (Ridley 1900). Unfortunately, natu
Leucanorchis multiflora, at the Bukit Timah rally occurring plants are now extinct.
Nature Reserve. A few years ago, a tiger orchid growing in the
Gardens flowered and was self-pollinated. The
Among the beautiful jewel orchid species re
huge seedpod was harvested 7 months later.
corded in Singapore are Anoectochilus alboli
Seeds germinated a month after being sown on
neatus and Macodes petola; and examples of
Knudson C medium (Knudson 1946). After 12
other native terrestrial orchids are Corymborkis
months in the laboratory, the seedlings were
veratrifolia and Phaius tankervilleae. Several
planted out in the nursery.
forest-floor primitive species also can be found,
Since the tiger orchid last occurred naturally
such as Apostatasia nuda and Neuwiedia vera
in Pulau Ubin, the first batch of seedlings was
trifolia.
reintroduced there in July 1999, when the seed
lings were 26 months old and ca. 15-20 cm tall
METHODS AND MATERIALS with 5-6 leaves. They were affixed on durian,
rambutan, mango, angsana, tembusu, and rain
Based on lists in a preliminary report on the trees. Seedlings also were planted on trees in the
conservation status of plants native to Singapore Botanic Gardens, around the Visitor Centre at
(Ng & Wee 1994, Tan 1995), ca. 170 of Singa the Bukit Timah Nature Reserve, and in the Or
pore's 221 species of native orchid species al chard Boulevard area in the heart of the city.
ready are considered to be extinct, and only four With experience from the initial trials, we de
are viewed as common. The remaining species cided to introduce seedlings to the Bukit Batok
are placed within the "Endangered," "Vulner Nature Park in early 2001. This time, the seed
able," and "Rare" categories or have an inde lings were more mature, ca. 30-40 cm tall with
terminate status. This means that more than 90% 16-20 leaves. They had at least three shoots, a
of the native orchids in Singapore are endan well-established root system, and fleshy pseu
gered, vulnerable, rare, or extinct. dobulbs. In February 2001, these larger seed
A comparison of habitats on the Island of Sin lings were planted on trees along Orchard Bou
gapore 150 years ago and today shows that most levard and on the yellow rain trees around the
of the mangrove and marshy areas have been Bandstand in the Botanic Gardens. In April
replaced by industrial estates or residential areas. 2001, seedlings of the same age were introduced
Forest and mangrove areas, such as those at to a site adjacent to a mangrove area in Pulau
SECOND IDCC PROCEEDINGS 79
TABLE l. Survival rate of reintroduced seedlings of ciosum. The size of seedlings (TABLE 1) also is
Grammatophyllum speciosum, the tiger orchid, to a key factor in determining survival. Seedlings
various parts of Singapore. with 16--20 leaves (30-40 cm tall) tend to sur
vive better than those with only five leaves (15-
Seedling Survival 20 cm tall).
size rate
We hope that the tiger orchids will continue
Location cm %
to thrive in their new homes. In the near future,
Pulau Ubin 15-20 35
more of this beautiful and majestic species will
30-40 90
find its way to more nature areas and parks in
Bukit Timah Nature Reserve 15-20 10
30-40 75 Singapore.
Botanic Gardens 15-20 10 In 2003 and 2004, two other native orchids,
30-40 70 Bulbophyllum vaginatum and B. membranaceum
Orchard Boulevard 15-20 45 were successfully propagated and reintroduced.
30-40 90 Seeds of these species were collected from
Bukit Batok Nature Park 30-40 90 plants growing in their natural habitats. The
Holland Road 30-40 95 seeds were sown on Knudson C medium. Seed
Upper Pierce Reservoir 30-40 95
lings were grown on the media until 2-3 cm tall
before being transferred to the nursery. Some ten
seedlings were planted on fern barks measuring
Ubin, and in early May 2001 again to the Bukit 7 cm long by 5 cm wide and grown at the nurs
Timah Nature Reserve. Some 40 seedlings also ery for 6 months, until new shoots began to de
were planted on rain trees along Holland Road. velop. They were then reintroduced. Host trees
In December 2002, some 40 seedlings were were selected based on the same criteria used
planted on trees at the Upper Pierce Reservoir. for reintroducing the tiger orchid. When a suit
In early 2004, some 20 plants were planted at able tree is selected, fern barks with established
various urban parks, such as Sembawang Park, seedlings were secured on the tree trunk by
Kent Ridge Park, and Tiong Bahru Park. Our nails.
aim is to use native orchids to educate the public Thus far, some 500 seedlings of Bulbophyllum
about our rich natural heritage and our respon vaginatum and B. membranaceum have been re
sibility to conserve it. introduced. More than 90% have settled down
The tiger orchid seedlings we planted have and are growing well in their new homes. We
been growing for 2-5 years in their new homes, have learned that these seedlings are best plant
and a majority of them are doing well. New ed in slightly shady areas, with at least 50%
shoots have developed, and roots are firmly es shade to avoid being scorched. We are very
tablished on tree trunks. Unfortunately, most pleased to report that most of these seedlings
seedlings planted in the Bukit Timah Nature Re have produced new shoots and are growing onto
serve were damaged or removed by animals the bark of the host tree.
(probably by squirrels and monkeys respective
ly) (TABLE 1). Orchid Cryo-Seed Bank
Several factors appear to play major roles in
the survival of introduced seedlings. These in The second conservation strategy is to store
clude the microclimate of the area (relative hu orchid seeds under liquid nitrogen as part of an
midity, for example), texture of the bark of host Orchid Cryo-Seed Bank Project. Why do we
trees, presence of other epiphytes, and the size store seeds in liquid nitrogen? Although tropical
of the seedlings. orchids have been grown routinely from seed for
Seedlings planted in areas with high relative many years, using the asymbiotic method for
humidity tend to survive better than those in dry seed germination, relatively little progress has
areas. For example, in Pulau Ubin, seedlings es been made in developing techniques for storing
tablished in a damp area inside a secondary for the seeds. Storage is becoming increasingly im
est are healthier and more vigorous than those portant, however, in view of the rapid loss of
growing near the sea where the breeze tends to many species caused by habitat destruction and
dry the bark faster. Texture of the bark is im over-collection. The reason for storing seeds un
portant because certain barks tend to retain more der such low temperature is simple. When plant
moisture. For instance, rain trees are generally and animal tissues are stored at ultra-low tem
better hosts than tembusu. Trees that. support peratures, such as that of liquid nitrogen
more epiphytes tend to be better hosts than those ( -196°C), metabolism is effectively stopped and
with fewer epiphytes. It seems that if the con cells are preserved without deterioration until
ditions are suitable for other epiphytes, they also such time as they are thawed for use.
are more appropriate for Grammatophyllum spe- There are several reasons for the cryopreser-
80 SELBYANA Volume 26(1,2) 2005
vation of orchid seeds: (1) Seed storage ensures healthy, mature seed capsules. (2) Desiccate the
against failure to germinate or the accidental seed for several days in a desiccator that con
loss of seedlings. (2) Instead of keeping hun tains a saturated solution and calcium chloride.
dreds of plants in the nursery, thousands of or (3) Transfer a small quantity of dried seeds to a
chid seeds (which are very small), can be stored 2-ml cryogenic vial. (4) Store the vial in a liquid
in a small container. If stored under the proper nitrogen freezer.
conditions, the seeds can be kept for years under To conclude, although remarkable progress
such conditions. The seeds can be sown as and has been made, cryobiological storage remains
when the need arises. The seeds also can be dis a relatively new science, but one which holds
tributed to (or exchanged with) other botanic in promise for the long-term storage of germplasm.
stitutions for conservation. (3) Seeds of hybrids The freezing of plant samples at a low temper
can be stored as well, once the technique is per ature is still in a highly empirical state. Cryo
fected. This will allow assessment of the com preservation offers a practical, efficient, and
economical tool for long-term storage of germ
mercial merits and potential of a particular cross
plasm. Tropical species cryopreservation has not
while still retaining a proportion of the seeds.
been studied extensively, because these plants
(4) Plant germplasm collections form an integral
are known to be more sensitive to chilling, low
part of all plant-breeding programs. The purpose
temperature, and desiccation than are temperate
of germplasm preservation is to ensure the avail
species. Therefore, a considerable amount of re
ability of useful germplasm at any time. Germ
search still needs to be conducted, before we can
plasm storage in the form of seeds is economical
use the technique confidently for long-term pres
and efficient.
ervation of orchid seeds. At the moment, we are
During the last 2 years, we carried out a series
experimenting to fine-tune the storage procedure
of experiments to investigate the optimal con
and determine if we can use it to store seeds of
ditions for storing some native orchid seeds. We
other species and hybrid orchids.
studied the effects of pre-storage treatment such
as desiccation, effectiveness of various desic
LITERATURE CITED
cants, duration of desiccation, age of seeds, and
different types of containers. Arditti, J. 1992. Fundamentals of Orchid Biology. Wi
Thus far, we have managed to successfully ley-Interscience, New York.
Keng, H., S.c. Chin, and H.T.W. Tan. 1998. The Con
store seeds of four native species. They are Den
cise Flora of Singapore. Vol. II: Monocotyledons.
drobium crumenatum, Spathoglottis plicata,
Singapore University Press, Singapore.
Bulbophyllum vaginatum, and Dendrobium an Knudson, L. 1946. A new nutrient solution for the ger
osmun. The first three species are still common mination of orchid seed. Amer. Orchid Soc. Bull.
in Singapore. The last one can no longer be 15: 214-217.
found in Singapore. To carry out the systematic Ng, P.K.L. and YC. Wee, eds. 1994. The Singapore
investigations, we need a large quantity of seeds; Red Data Book: Threatened Plants & Animals of
Singapore. Nature Society (Singapore), Singapore.
hence the three common species were used.
Ridley, H.N. 1900. Flora of Singapore. J. Straits
Some of the seeds have been stored under liquid
Branch Roy. Asiatic Soc. 33: 27-196.
nitrogen for more than 24 months. Recently, we Tan, H.T.W., ed. 1995. A Guide to the Threatened
attempted to germinate the stored seeds and are Plants of Singapore. Singapore Science Centre,
pleased to report that more than 90% of the Singapore.
seeds remained viable. This gives us a great Tan, W.K. 1984. Orchid species of Singapore. pp. 8-
sense of excitement. Seeds of tropical orchids 12 in Proceedings of the Fifth Asian Orchid Con
gress. Park and Recreation Department, Ministry
can be preserved under - 196°C after all! From
of National Development, Singapore.
the results of the experiment, we find the best
Yam, T.W. and M.A. Weatherhead. 1988. Germination
procedure for storing the seeds that we have test and seedling development of some Hong Kong
ed is as follows: (1) Collect fresh seeds from orchids. I. Lindleyana 3: 156-160.