New species Dendrobium tuananhii - Another Interesting New Orchid from Vietnam

Distribution area of Den. tuananhii in Vietnam

Recent botanical explorations of Vietnam brought forth numerous exciting discoveries. Among them are such outstanding orchids as Christensonia vietnamica, Vietorchis aurea, Zeuxinella vietnamica, Renanthera citrina, Renanthera vietnamensis, Paphiopedilum helenae, Paphiopedilum hangianum, Paphiopedilum tranlienianum, Paphiopedilum vietnamense and a great number of other species (Haager, 1993; Christenson,2001; Averyanov, Averyanova, 2003; Averyanov et al., 2003). Dendrobium tuananhii, described below, represents one more bright and important addition to this group of plants. This species was discovered in 2002 by Vietnamese orchid enthusiast and explorer Tran Tuan Anh in a rocky limestone region of Lai Chau province in the northwestern extremity of the country and is named after him. This orchid was observed as a very rare epiphyte in rather dry broad-leaved evergreen forest on rocky remnant mountains composed of solid crystalline highly eroded limestone of Paleozoic age. Plants were found in an elevation belt between 2,625 and 3,281 feet (800 and 1,000 m) above sea level. Climate and natural conditions of similar habitats were described in details in our previous publications for some Paphiopedilum species occurring in the same area (Averyanov et al., 2003).

Rather dry broad-leaved evergreen forest on rocky remnant limestone at an elevation to feet (800 to 1,000 m) above sea level is the habitat of Den. tuananhii. A flowering specimen of Dendrobium tuananhii, a new species discovered in 2002 in Vietnam Close up of Den. taunanhii Close up of the flower, lip and anther of Den. tuananhii The habit of Den. tuananhii

According to field observations, Den. tuananhii is a very rare orchid. It blossoms in the spring, especially March through April. Mature leafless pseudobulbs commonly have one to four inflorescences, each with one to three large glossy waxy pink to pinkpurple flowers. The clustered pseudobulbs usually do not exceed 3/4 2 to 51/2 inches (2 to 14 cm) long and a plant that is compact and miniature may sometimes develop numerous flowers that open simultaneously and last more than a month. Miniature habit and numerous large, waxy, long-lasting flowers show this species to have great potential for ornamental cultivation and breeding.

Taxonomically, Den. tuananhii is a rather isolated species without clear close relatives. According to basic flower structure, it can be placed in Section Breviflores Hook.f. I do not know, however, of any species in this Section that might be closely related to our plant. It is easy to recognize Den. tuananhii by habit structure (even without flowers) because of its strongly compressed flattened pseudobulbs. No other Dendrobium species in mainland Southeast Asia has such strange, unusual and peculiar pseudobulbs.

The distribution of Den. tuananhii is limited. It probably comprises a small region in the northern part of Lai Chau Province near the Chinese border. This new species obviously presents another example of limited strict endemism in the flora of Vietnam.

Dendrobium tuananhii Aver., sp.nov.

Species haec sectione Breviflores Hook.f. pertinent, sed speciebus sectionis alliis pseudobulbia dorsiventraliter valde compressis, floribus magnis late apertis, nec non labelli structura differt.

Description

Epiphytic herb with clustered erect pseudobulbs arising from short creeping horizontal rhizome. Pseudobulbs flat, strongly dorso-ventrally compressed, 4–12(–15) cm long, 0.8–1.5(–2) cm wide, composed of 4–12(–15) internodes, covered at the base by colorless papyraceous sheaths. Leaves three to eight, oblong, broadly acute, narrowing toward the base, 3–8 cm long, 0.8–1.5 cm wide. Inflorescences appear on leafless pseudobulbs from nodes along lateral margin, 1–2(–3) flowered. Scape and rachis green, 2–8 mm long, 2–3 mm thick. Flower bracts colorless, papyraceous, ovate with broad base and acute apex, 4–6 mm long, 3–4 mm broad. Pedicel and ovary 5–6 cm long, 2–3 mm thick, light green to white. Flowers thick, waxy and glossy, odorless, widely opening, 4–5 cm in diam. Median sepal light pink-purple to pink-purple or light violet with white base, oblong, 2–2.4 cm long, 11–13 mm wide. Lateral sepals triangular, with broad base forming broad mentum 1– 1.2 cm long and about 1 cm broad, acute at the apex, slightly reflexed, light pink-purple with white basal half and yellow center at the base, 2.3–2.6 cm long, 1.4–1.6 mm wide. Lateral petals rhomboid with irregularly undulated margin in apical half, light pink-purple to light purple-violet with white base, truncate or slightly emarginate at the apex, 2.2–2.5 cm long, 1.4–1.6 cm wide. Lip strongly recurved, movably articulated with column-foot apex, three-lobed, deep purple-brown with olive-yellow margin of lateral lobes, 12 mm long, 14 mm wide (when flattened), with large black fleshy glossy, finely papillose callus, which bears three low thick keels, median of which longer and reaches middle of lip mid-lobe, lateral lip lobes obliquely ovate, 8 mm long, 4 mm wide, median lobe obovate, truncate to slightly emarginate at the apex, 6–7 mm long, 5–6 mm wide, densely woolly hairy above, hairless glossy on lower surface. Column light green short and broad, 2.5–3 mm tall, 4 mm broad, with hemispheric callus on the apex on dorsal side and denticulate margin of clinandrium; stigma green, sub*quadrate. Column-foot slightly recurved, longitudinally concave, with prominent warty transversal ridge below middle, 8–10 mm long, 5–6 mm wide, light yellow-green, with finest purple-brown marks inside at the middle, deep purple-brown at apical part. Anther light green, oblong, 3.5–4 mm long, about 3 mm wide, distinctly bifid at the apex, with short narrowing base. Fruit unknown.

Type

 Northern Vietnam, Prov. Lai Chau, District Muong Te, about 15 km to the east of Muong Te town, epiphyte on high tree on limestone mountain, at elevation about 800 to 1,000 m a.s.l. Coll. Tran Tuan Anh in 2002. Flowered in Hanoi March 15–April 11, 2003. Type herbarium prepared by Prof. P.K.Loc, P-10620 (holotype: HN).

Dissusion

Dendrobium tuananhii belongs to Section Breviflores Hook.f., and differs from all species of this section in flat, strongly flattened compressed pseudobulbs, large widely open flowers and structure of the lip.

Acknowledgments

I would like to express our deep thanks to Tran Tuan Anh and Phan Ke Loc for  materials used in this paper.

References

Averyanov, L.V., and A.L. Averyanova. 2003. Updated Checklist of the Orchids of Vietnam. Vietnam Nat. Univ. Hanoi.
Averyanov, L.V., P.Cribb, P.K.Loc, and N.T.Hiep. 2003. Slipper Orchids of Vietnam. With an Introduction to the Flora of Vietnam. Royal Bot. Gard. Kew.
Christenson, E.A. 2001. The genus Christensonia Haager. Lankesteriana. 2:19–21. Haager, J.R. 1993. Some new taxa of orchids from Southern Vietnam. Orchid Digest. 57(1):39–44.

Leonid Averyanov, PhD, who has explored Vietnam extensively, has coauthored two books of interest to orchid enthusiasts: Slipper Orchids of Vietnam (with P. Cribb, P. Ke Loc and N. Tien Hiep. 2003) and Updated Checklist of the Orchids of Vietnam (with Anna L. Averyanov. 2003). Leonid has been the recipient of research grants from the American Orchid Society, the most recent of which was approved by the Society’s trustees at the 2003 AOS Fall Members Meeting in Sacramento, California. Komarov Botanical Institute of the Russian Academy of Science, Prof. Popov St., 2, St.-Petersburg 197376, Russian Federation. (This article describing a new species was peer-reviewed. -Editor.)

Dendrobium tuananhii Aver.
A. Flowering plant. B. Inflorescence and flower (front view). C. Pedicel and flower (side view). D. Lip, unfolded sepals, and lateral petals. E. Lip, frontal view. F. Lip, view from behind. G. Lip, side view. H. Unfolded apical part of the lip, frontal view. I. Hairiness on the apical part of the lip. J. Lip, sagittal section. K. Column, side view. L. Column, frontal view. M. Apical part of the column without anther cup, frontal view. N. Anther cup from below. O. Anther cup, view from above (all drawn by the author from the Type: P.K.Loc P-10620).
Photographs án Illustration by L. Averyanov

Leonid V. Averyanov
Komarov Botanical Institute of the Russian Academy of Sciences

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