Journal of Threatened
Taxa | www.threatenedtaxa.org | 26 August 2025 | 17(8): 27384–27390
ISSN 0974-7907 (Online) | ISSN 0974-7893 (Print)
https://doi.org/10.11609/jott.9588.17.8.27384-27390
#9588 | Received 26 December 2024 | Final received 18 March 2025 |
Finally accepted 07 August 2025
Re-collection of two climbing
asclepiads: Cynanchum corymbosum
and Oxystelma esculentum
(Apocynaceae: Asclepiadoideae)
from Assam, India
Gitartha Saikia
1, Saurav Kumar Boruah 2, Trishna
Roy Prodhani 3 &
Nilakshee Devi 4
1,2,4 Plant Taxonomy Laboratory,
Department of Botany, Gauhati University, Guwahati,
Assam 783314, India.
3 Department of Botany, Abhayapuri College, Bongaigaon,
Assam 783384, India.
1 geetugitartha@gmail.com
(corresponding author), 2 skboruah19@gmail.com, 3 trishnaprodhani123@gmail.com,
4 devinilakshee@gmail.com
Editor: Vivek Pandi, Manipal Academy of Higher Education, Karnataka,
India. Date of publication: 26 August 2025
(online & print)
Citation: Saikia, G., S.K. Boruah, T.R. Prodhani
& N. Devi (2025). Re-collection of two climbing asclepiads: Cynanchum
corymbosum and Oxystelma
esculentum (Apocynaceae:
Asclepiadoideae) from Assam, India. Journal of Threatened Taxa 17(8): 27384–27390. https://doi.org/10.11609/jott.9588.17.8.27384-27390
Copyright: © Saikia et al. 2025. Creative Commons Attribution 4.0
International License. JoTT allows unrestricted use,
reproduction, and distribution of this article in any medium by providing
adequate credit to the author(s) and the source of publication.
Funding: No external funding was received for this research.
Competing interests: The authors declare no competing interests.
Acknowledgements: The authors are grateful to the head, Department of Botany, Gauhati University, for providing the necessary facilities to conduct this research. Authors also extend their sincere gratitude to Mr. Monish Kumar Thapa, PhD research scholar, Department of Zoology, Assam Royal Global University, for the identification of the insect pollinators documented during the study and Mr. Arup Jyoti Bora, researcher, Department of Geography, Gauhati University for his ample guidance in preparing the location map.
Abstract: Two lesser-known climbing
asclepiads—Cynanchum corymbosum
Wight and Oxystelma esculentum
(L.f.) Sm.—of the family Apocynaceae,
sensu lato, have been
recollected from Assam, India after a gap of 67 and 87 years, respectively. A
detailed taxonomic account, colour photo plates, and
a map showing the collection sites in Assam has been provided. This
recollection highlights the importance of continued botanical exploration and
conservation efforts in the region.
Keywords: Climbers, conservation, Gentianales, pollinators, plant diversity.
Asclepiads are the fascinating
group of plant kingdom belonging to the subfamily Asclepiadoideae
under the family Apocynaceae, sensu
lato (Endress 2016; Demarco 2017). They are characterised by having more complex and elaborate floral
organization among the eudicots (Endress 2016). Via extreme floral synorganization, the asclepiads led to the evolution of
floral organs (Demarco 2017). The presence of corona, gynostegium,
and pollinaria bearing two pollinia distinguish the
asclepiads from other Apocynaceous members of plant
domain (Swarupanandan 1996; Endress & Bruyns 2000; Endress 2016). Furthermore, asclepiads exhibit
a wide array of habits ranging from herbs, shrubs, climbers to epiphytes;
commonly distributed in the tropical areas.
Cynanchum L. and Oxystelma
R.Br. are two climbing genera of asclepiads native to the tropics and
subtropics, belonging to the family Apocynaceae under
the subfamily Asclepiadoideae, and the tribe Asclepiadeae (Endress & Bruyns
2000; Endress et al. 2014). Cynanchum L. is a
widespread genus of the tropics consisting of 259 globally accepted species
(POWO 2024). Members of the genus are usually twiners, bearing basally cordate
leaves and prophylls with annulated gynostegial
staminal corona often forming cup shaped interstaminal
corona (Liede & Kunze 1993; Liede
& Meve 2013; Shen et al. 2019; Xu et al. 2021).
While, Oxystelma R.Br. is a little-known genus
of the family habituated by climbing herbs bearing campanulate flowers with
pointed corolline corona comprising only two globally
accepted species (POWO 2024).
During a field survey to Bongaigaon and Kamrup districts
of Assam during the month of October and November in 2024, the authors encountered
two climbing asclepiad taxa bearing milky latex and flowers with distinct
corona, and pollinarium. Further taxonomic investigation of the collected
specimens, the climbers were identified as Cynanchum
corymbosum Wight and Oxystelma
esculentum (L.f.) Sm.
Upon consultation of the available literature and herbarium specimens, it was
revealed that both the species are the recollection from the state after a gap
of 67 and 87 years, respectively.
Cynanchum corymbosum Wight was first described by Robert
Wight in ‘Contributions to the Botany India’ in the year 1834. In Assam, the
species was first collected by U.N. Kanjilal in 1915
from Darrang District of Assam. Subsequently, G. Panigrahi collected the same species from Kakoi Reserve Forest of North Lakhimpur District of Assam
in 1957. Following this collection, no further records of the species has been
reported from Assam. Therefore, the
present collection is a re-collection of the species Cynanchum
corymbosum Wight from the state after a gap of 67
years.
The genus Oxystelma
R.Br. was first described by R. Brown in ‘Prodromus
Florae Novae Hollandiae et Insulae van-Diemen’ in the
year 1810. Later on, James Edward Smith in 1813 validly published the name Oxystelma esculentum
(L.f.) Sm. based on the type species Periploca esculenta L.fill. (1781). The first collection of the species
from Assam was made in 1868 from Goalpara District
(K001129273!). After the collection, G.K. Deka again collected the species from
the same locality in 1937, marking the last reported collection from the state.
Hence, the present collection of the species Oxystelma
esculentum by the authors reported the
recollection of the lesser-known asclepiad taxon from Assam after a break of 87
years.
Materials and Methods
The plant specimens were
collected during October and November, 2024.
Morphological observations of the climbers were recorded and colour photographs showing the habit of the plant has been
taken at their natural habitats. Floral parts were dissected and photographed
under the Labomed stereo zoom microscope. Further
specimens were identified by consulting relevant literatures (Hooker 1883; Kanjilal et al. 1939; Deb 1983; Singh et al. 2012) and
accessing available herbarium specimens housed at CAL, ASSAM, ARUN, and other
online databases (https://www.gbif.org/; https://plants.jstor.org/). Voucher
specimens were prepared following the standard herbarium techniques of Jain
& Rao (1976), and submitted at ASSAM, and Gauhati
University Botanical Herbarium (GUBH). A detailed taxonomic descrip-tion
of the collected species with colour photoplates and a location map showing the collection sites
of the species have been provided.
Taxonomic Treatment
Cynanchum corymbosum
Wight, Contr. Bot. India:
56.1834; Hook.f. Fl. Brit. India. 4:24.1883; Kanjilal et al. Fl. Assam 3:286.1939; Deb, Fl. Tripura
State 2:31.1983
Description
Climbing shrub, stem terete;
twinning; glabrous. Internodes 12–16 cm long. Latex milky. Leaves opposite,
ovate, glabrous, abaxially pubescent along the veins; apex acuminate, base
cordate, margin ciliate, lateral veins 4–6 pairs, lamina 10–11 × 7–7.8 cm;
petiole terete, 5–5.5 × 2–3 mm. Prophylls deciduous, orbicular with cordate
base, apex apiculate, 0.7–1 × 0.6–1.1 cm.
Flowers many, arranged in corymbiform cymes, peduncle slender, 2.5–3 cm
long; Pedicel 0.8–1cm long, Bract ovate triangular, apex acute, abaxial side
pubescent, glabrous adaxially, 1−1.2 × 0.8 mm. Calyx 5-lobed, lobes 1.8−2 ×
1.3−1.6 mm, ovate, apex acute, glabrous, green. Corolla campanulate, tube
short, 1−1.2 mm long, lobes 5, linear, apex acute, glabrous, margin slightly
recurved abaxially, 4.5−5.2 × 2−2.2 mm. Interstaminal
corona cupular, shiny white, mouth with irregular
incinerates, 3.8–4 × 2−2.4 mm, arises from the base of staminal corona;
staminal corona five lobed, 1.2−1.5 mm, fused with anther cap. Gynostegium 2 × 1.3 mm, stigma pentagonal, creamy white, 1.2−1.3
mm long, laterally surrounded by five anther caps; anther cap rhomboid ovate,
papery white, 0.6−0.8 × 0.4−0.6 mm; pollinarium five, inserted within anther
caps, pollinia pendulous, elliptic, golden yellowish, glossy, 328−352 × 165−178
μm; caudicle short,
corpusculum shiny red, 310–323 × 154–176 μm. Pistil
2.5−2.7 mm, stigma rhomboid, capitate, 1.2−1.3 mm long, style slender 1.5 mm
long. Follicles lanceolate, 12−14 × 4−5.5 cm, covered with dense long fleshy
spines. Seeds comose, 1−1.2 × 0.6−0.8 mm, ovate
orbicular, margin dentate crenate, coma silky white.
Flowering and Fruiting:
August–October (Flowering), October–December (Fruiting).
Habitat: Roadside forests and
scrub jungles.
Distribution: Thailand, Vietnam,
Cambodia, Bangladesh, Eastern Himalaya [China, Myanmar, northeastern India
(Assam, Tripura)], Nicobar Island.
Specimen examined: BANGLADESH,
Sylhet, coll. Wight., Wall. Asclep. no. 81(K),
K000894620! (Isotype); INDIA, Assam, Darrang, 6.i.1915, coll. U.N. Kanjilal
[ASSAM]; Lakhimpur, Kakoi RF, 22.xi.1957, G. Panigrahi [ASSAM]; Kamrup, Hajo, 26.245o N, 91.588o E, 2 October
2024, coll. G. Saikia GSL08 (ASSAM); Bongaigaon, Kakoijana RF, 26.471o
N, 90.639o E, 5.xi.2024, coll. G. Saikia
GSL09 (GUBH) [Present report].
Note: The specimen was collected
from two locations, the roadside forest areas of Kakoijana
RF, Bongaigaon, and Pakorkona
region of Hajo, Kamrup District
of Assam. The plant was found to climb on the bamboos, Senna siamea, Ficus hispida, Tectona grandis, and twinning with other climbers such as Ichnocarpus frutescens,
Mikania micrantha, Paederia
foetida, Stephania japonica, and Tinospora cordifolia. Remarkably,
in both the collection sites the Common Leopard Butterfly Phalanta
phalantha and Common Swift Pelopidas agna belonging to the order Lepidoptera were found as
the common pollinators of the species. The common Black Garden Ant Lasius niger has
been noticed as the pollinator in the Pakorkona area
of Kamrup District (Image 3). Additionally, fruits of
the genus Cynanchum are usually solitary
(Khanum et al. 2016). In the present collection fruits bearing a pair of
follicles have also been recorded (Image 4).
Oxystelma esculentum
(L.f.)
Sm. A.Rees, Cycl. 1. 25: 1813; Periploca
esculenta L.f., Suppl. Pl. 168 (1781); O. esculentum (L.f.) R.Br. Hook.f. Fl. Brit. Ind. 4:17:1883; Kanjilal
et al. Fl. Assam 3: 281: 1939; Sinha et al. Fl. Mizoram 2: 108: 2012
Description
Climbing or twinning herb. Stem
terete, glabrous, green; internodes 2−10 cm long. Latex milky. Leaves opposite;
lamina linear lanceolate, oblong, apex acute, base cuneate, glabrous, midvein
distinct, 10–15 × 0.8−1.2 cm, lateral nerves 9−10 pairs; petiole 5−8 mm long.
Inflorescence drooping, lateral or axillary, 1−6 flowered raceme; peduncle
glabrous, 2.5−5.2 cm long. Flowers campanulate, 2.8−3.2 × 2−2.2 cm, pedicel
1−1.4 cm long, reddish-green. Bract ovate elliptic, apex acute, pubescent
abaxially, adaxial side glabrous, 4.5−5 × 1.2−1.5 mm. Calyx five lobed, divided
up to base, lobes ovate lanceolate, glabrous within, glandular outside, apex
acute, faintly reddish, 5.2−5.5 × 1.2−1.4 mm. Corolla campanulate, articulated with
purple veins on inner side, outer side creamy white, without purplish veins;
tube 6−8 mm long, five lobed; lobes triangular, apex acute, margin ciliate with
white dense hairs, 1−1.3 × 0.5−0.7 cm. Corona two types; outer coroline, lobes five, uniseriate,
fleshy, creamy white, arises from the base of corolla tube, apex undulate,
pointed, 5.2−6 × 1.2−1.5 mm; staminal corona scaly, 5-lobed, adnate to the
staminal column, apex acute, tip keeled incurved, basaly
inflated, fused with anther cap. Gynostegium 4.8−5.2
× 3.8−4 mm, stigma pentagonal, light green, surrounded laterally by five anther
caps. Anther cap obovate elliptic, outerside membraneous, adaxially glabrous with two distinct ridges. Pollinarium
five, inserted within anther caps with a pair of pollinia, caudicles
short; corpusculum elliptic, dark brown, 284−287 × 108−113 μm;
pollinia pendulous, glossy, oblanceolate, golden yellow, 1116−1130 × 358−366 μm. Fruits and seeds not seen.
Flowering and Fruiting:
August–October (Flowering), September–December (Fruiting).
Habitat: Wet habitats near
wetlands and ditches.
Distribution: India (Assam),
Bangladesh, Myanmar, Nepal, China, Cambodia, Thailand, Vietnam, Sri Lanka,
Pakistan, western Australia
Specimen examined: INDIA, Assam, Goalpara, 17.viii.1868, [Cat no.
8219], K001129273!; Goalpara, 8.ix.1937, coll. G.K.
Deka [ASSAM]; Kamrup: Khamrenga
beel, Chandrapur, 26.223o N, 91.923o E,
coll. G. Saikia, 28.x.2024, coll
no. GSL07 (ASSAM) [Present report].
Note: The specimen was collected
from the Khamrenga wetland of Kamrup
District of Assam, an extended portion of Amchang WS.
At the collection site, only a few individuals were documented twinning on Chrysopogon zizanioides
and Phragmites karka thriving near the
wetland. The common Honey Bee Apis melifera, common Ant Mimicking Spider Castianeira zetes,
and the common Black Garden Ant Lasius niger were observed as the pollinators of the species
at the collection site.
Conclusion
Recollection of these two lesser
known asclepiadoid taxa Cynanchum
corymbosum and Oxystelma
esculentum from Assam after a gap of more than 60
years affirms the continued distribution of the species within the state.
Occurrence of very limited populations of the species Oxystelma
esculentum at the collection site entails an
immediate attention regarding the conservation of the species in the wild.
Additionally, enquiry into the pollinators of these asclepiads for insights
into the pollination biology will reveal better understandings regarding the
pollination behaviour of this fascinating group of
plants.
For
figure & images - - click here for full PDF
References
Deb, D.B.
(1983). The Flora
of Tripura State. Today & Tomorrow’s Printers and Publications, New
Delhi (2): 333 pp.
Demarco, D. (2017). Floral glands in
asclepiads: structure, diversity and evolution. Acta Botanica Brasilica 31(3): 477–502. http://doi.org/10.1590/0102-33062016abb0432
Endress, M.E.
& P.V. Bruyns (2000). A Revised Classification of the Apocynaceae s.l. The Botanical
Review 66(1): 1–56.
Endress, P.K.
(2016). Development
and evolution of extreme synorganization in
angiosperm flowers and diversity: a comparison of Apocynaceae
and Orchidaceae. Annals of Botany 117:
749–767. https://doi.org/10.1093/aob/mcv119
Endress,
M.E., S.L. Schumann & U. Meve (2014). An updated classification for Apocynaceae. Phytotaxa
159(3): 175–194. https://doi.org/10.11646/phytotaxa.159.3.2
Hooker, J.D.
(1883). The Flora
of British India, Vol. 4. Library University of California, Davis.
Henrietta Street, Covent Garden, London, 17, 24 pp.
Jain, S.K.
& R.R. Rao (1976). A Handbook of Field and Herbarium Methods. Todays &
Tomorrows Printers and Publishers, New Delhi, India.
Kanjilal, U.N., A. Das, P.C. Kanjilal & R.N. De (1939). Flora of Assam, Vol. 3. Lakshminarayan Nath, Prabasi
Press, Upper Circular Road, Calcutta, 281, 282, 286 pp.
Khanum, R.,
S. Surveswaran, U. Meve
& S.L. Schumann (2016). Cynanchum (Apocynaceae:
Asclepiadoideae): a pantropical Asclepiadoid
genus revisited. Taxon 65(3): 467–486. https://doi.org/10.12705/653.3
Liede, S. & H. Kunze (1993). A descriptive system for corona
analysis in Asclepiadaceae and Periplocaceae.
Plant Systematics and Evolution 185: 275–284.
Liede, S. & U. Meve
(2013). The Orthosiinae revisited (Apocynaceae,
Asclepiadoideae, Asclepiadeae).
Annals of the Missouri Botanic Gardens 99(1): 44–81.
POWO (2024). “Plants of the World Online.
Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:453597-1.
Accessed on 28.xi.2024
Shen, J.Y.,
X.D. Ma, W.G. Wang & J.P. Shi (2019). Cynanchum
brevipedunculatum, a new species of Apocynaceae from Yunnan, China. Taiwania
64(3): 217–220. https://doi.org/10.6165/tai.2019.64.217
Singh, K.P.,
G.P. Sinha, B.K. Shukla, G. Chowdhury & D. Banik
(2012). Flora of
Mizoram, pp. 337–340. In: Sinha, G.P., D.K. Singh & K.P. Singh (eds). Botanical Survey of India, Shiva Offset Press, Dehra
Dun.
Swarupanandan, K. & J.K. Mangaly (1996). The subfamilial
and tribal classification of the family Asclepiadaceae.
Botanical Journal of the Linnean Society 120:
327–369.
Xu, W.B., B.S. Xia, J.Q. Wu, Y.X.
Chen & J.Y. Shen (2021). Cynanchum hubeiense
(Apocynaceae), a new species from Hubei, China. Taiwania 66(1): 53–56. https://doi.org/10.6165/tai.2021.66.53