Robiquetia binhii Aver., V.C.Nguyen & Vuong, 2025

Averyanov, Leonid V., Nguyen, Van Canh, Vuong, Truong Ba, Quang, Bui Hong, Nguyen, Khang Sinh, Le, Tuan Anh, Binh, Tran Duc, Maisak, Tatiana V. & Nguyen, Cuong Huu, 2025, New orchids in the flora of Vietnam X (Orchidaceae, Orchidoideae, tribe Orchideae, Epidendroideae, tribes Gastrodieae, Arethuseae, Cymbidieae, and Vandeae), Phytotaxa 681 (1), pp. 20-54 : 45-46

Robiquetia binhii Aver., V.C.Nguyen & Vuong , sp. nov.

( Fig. 13 & 14 )

Diagnosis: —The new species differs from morphologically most similar R. succisa in oblong lanceolate or oblong broadly lanceolate leaves, with almost round apical lobes, light brown tepals and pure white lip, distinct flat callosity on petals, prominent pocket-shaped callus on adaxial side of lip side lobes, two longitudinal ridges inside lip as tall as long, back-wall and front-wall of spur with large callus almost closing spur entrance, and half-ovate rostellum, distinctly longer than tall.

Type: — VIETNAM. Kon Tum Province: probably Kon Plong District, epiphyte in evergreen forest, at elevation of about 700 m a.s.l., 2 August 2023, Nguyen Van Canh, AL 2235 (holotype LE: LE 01253912 https://en.herbariumle.ru/?t=occ&id=213892, photos & drawings LELE 01124287 https://en.herbariumle.ru/?t=occ&id=185344, LE 01124838 https://en.herbariumle.ru/?t=occ&id=221625, LE 01124839 https://en.herbariumle.ru/?t=occ&id=221626).

Description: —Perennial monopodial epiphytic herb. Stem simple or basally branched, rigid, leafy throughout, pendulous, (6)10–16(18) cm long, (3)3.5–5(6) mm in diameter (2–3 mm when dry), in basal half with few wiry, rigid, flexuose, terete, white, light grey to pale greenish roots, (3.5)4–4.5(5) mm in diameter (1.5–2 mm when dry); internodes (0.8)1.2–1.8(2.2) cm long. Leaves numerous, sessile, coriaceous, straight to slightly curved, oblong lanceolate to broadly lanceolate, (7)9–12(14) cm long, (0.8)1–2(2.2) cm wide, unequally bilobed at apex, with almost round lobes. Inflorescence pendulous raceme or panicle with 2–3 branches, (13)15–20(22) cm long, scape and rachis grassy green, in basal part with dirty purple markings; scape (3.4)4–8(10) cm long, terete, down curved at base, with (2)3–4(5) short, broad, dull pale yellowish brownish sterile papyraceus bracts (3)4–6(7) mm long; inflorescence branches to 10 cm long; rachis straight or slightly curved, longitudinally ridged, greenish with dirty purple markings, to 20 cm long, with many spirally arranged, subdense flowers. Floral bracts pale greenish to dirty purple, narrowly triangular, acuminate, somewhat scarious, (1.2)1.5–2.2(2.5) mm long, (0.4)0.5–0.6(0.8) mm wide. Pedicel and ovary (3.5)4–7.5(8) mm long and (0.6)0.8–1(1.1) mm in diameter (about 0.5 mm when dry), longitudinally ridged, light greenish, glabrous or with small scattered rusty trichomes, straight or slightly curved, slightly broadening at the base. Flowers widely opening, (6)6.5–7.5(8) mm across; sepals and petals rather fleshy, light brown, with white base; sepals outside with sparse very small rusty trichomes, lip, column, and anther cap entirely white; pollinia light yellow. Median sepal forward directed, broadly ovate, cucullate, strongly concave, almost hemispheric, round at slightly recurved apex, (3.3)3.5–4(4.2) mm long and wide (2.5–3 mm when dry). Lateral sepals spreading to reflexed, obovate, slightly oblique and concave, rounded at apex, (3.8)4(4.2) mm long, (3.3)3.5(3.7) mm wide. Petals forward directed, narrowly obovate, truncate, (2.4)2.6–3(3.2) mm long, (1.6)1.8–2(2.2) mm broad (about 2.5 × 1.8 mm when dry), slightly oblique, finely irregularly denticulate along margin, in apical half with flat round callosity. Lip spurred, (6.3)6.5–7(7.2) mm long (from spur apex to the apex of median lobe), 3-lobed; side lobes almost half-round, parallel and forward directed, (1.4)1.6–1.7(1.9) mm long, (1.9)2–2.2(2.3) mm broad at the base, each side lobe inside at front with prominent fleshy pocket-shaped callus; median lobe fleshy, conoid, (1.8)2(2.2) mm long, (0.7)0.8–0.9(1) mm wide, obtuse, forward directed or slightly upright, at middle with prominent, short, erect, longitudinal twin ridge (0.7)0.8(0.9) mm tall, median part of the disk with 2 fleshy, short, tall keels, separated by deep longitudinal furrow; spur rectangular obovoid, slightly dorsiventrally compressed, narrowing at the base, saccate, truncate or slightly emarginate at apex, (2.2)2.5–3(3.2) mm long and wide, inside with incomplete longitudinal septum rising from back-wall and front-wall in the spur middle part. Back-wall callus in form of large, simple. massive callosity almost closing the spur entrance. Column short, broad, slightly back bent, (1.8)2(2.2) mm high and wide; at the base from each side with large, fleshy, shortly cylindric or conoid, forwarddirected, finely verruculose auricles; at front with large, forward directed rostellum in form of half-ovate, laterally compressed, twin keel, supporting distally viscidium; stigma concave, obscurely cordate. Operculum placed at front of column, bail-shaped, 2–2.2 mm long, 0.8–0.9 mm broad, convex, with narrowly triangular beak, tapering to the acute apex. Pollinia 2, ovoid or ellipsoid pollinia, 0.5–0.55 mm long, each distinctly notched; stipe (tegula) in form of simple, almost filiform conduplicate stalk, (2.1)2.2(2.3) mm long, slightly broadening at arcuate bent apex; caudicles insignificant; viscidium attached to the stipe base, simple, in form of ovate flat, very small plate, about 0.2 mm long. Fruits not seen.

Etymology: —The species epithet refers to the name of Mr. Nguyen Truong Binh for his notable role in forest protection and nature conservation in Central Highlands of Vietnam.

Ecology and phenology: —Primary and secondary submountain and mountain evergreen broad-leaved forests on granite. Flowers in July–August.

Distribution: — Vietnam, Kon Tum Province (probably Kon Plong District). Endemic to central Vietnam.

Conservation status: —The species is known up to now only by a single collection from eastern part of Kon Tum Province in southern Vietnam. Any data on the size and geographical extension of the species’ population are not yet available. Hence, the conservation status of the new species is currently identified as Data Deficient (DD). Further field studies are necessary to assess the true conservation status of this rare species.

Notes: —New species is most close to R. succisa ( Lindley 1826: tab. 1014) Seidenf. & Garay in Seidenfaden (1972: 119) common in Nepal, NE India , Bangladesh, Myanmar, S China (including Hong Kong and Hainan), Thailand, Laos, Cambodia, and Vietnam. From this widespread species our plant differs in leaves oblong lanceolate to broadly lanceolate, 7–14 cm long, 0.8–2.2 cm wide, with almost round apical lobes (vs. leaves oblong elliptic or oblong narrowly ovate, 5–10 cm long, 1.5–2.5 cm wide, with triangular truncate apical lobes irregularly denticulate along the margin), light brown tepals and pure white lip (vs. tepals yellow or yellow green, lip white with bright purple stripes at the base of side lobes and yellow spur), distinct flat callosity on petals (vs. petals flat), prominent pocket-shaped callus on adaxial side of lip side lobes (vs. side lobes almost flat), two short and tall, longitudinal ridges inside lip, each as tall as long (vs. lip with low keels, much longer than tall), back-wall and front-wall of spur with large callus almost closing spur entrance (vs. back-wall and front-wall of spur with rather insignificant not closing spur entrance), and half-ovate rostellum, distinctly longer than tall (vs. rostellum half-orbicular, as long as tall or taller). Most probably the new species represents local endemism of mountain area in central part of southern Vietnam known in national geography as Central Highlands.

Additional studied specimen (paratype):— VIETNAM. Kon Tum Province: probably Kon Plong District, epiphyte in evergreen forest, at elevation of about 700 m a.s.l., 27 August 2023, Truong Ba Vuong, Nguyen Van Canh, BVL1893 (VNM VNM00070010).

Figures

FIGURE 13. Robiquetia binhii. A. Flowering plant in cultivation. B. Flattened plant flowering plant. C. Leaf apex, adaxial side. D, E. Inflorescences. F. Portion of inflorescence. G. Flower, front view. H. Flower, side view. I, J. Median sepal, adaxial and abaxial side. K. Lateral sepals, adaxial and abaxial side. L. Petals, adaxial and abaxial side. M. Column and lip, front view, operculum removed. N. Column and lip, view from above, operculum and pollinarium removed. O. Column and lip, front view, spur, operculum and pollinarium removed. P. Ovary, column and lip, side view, operculum removed. Q. Column and lip, side view, spur, operculum and pollinarium removed. R. Ovary, column and lip, sagittal section. S. Operculum, view from above and from below. T. Pollinaria, view from different sides. All photos from the plant used for the preparation of the holotype specimen Nguyen Van Canh, AL2235 by Van Canh Nguyen and Truong Ba Vuong. Photo correction and design by L. Averyanov and T. Maisak.

FIGURE 14. Robiquetia binhii. A. Flowering plant. B. Inflorescence. C. Portion of rachis, floral bract, pedicel and flower, side view. D. Flower, side view, lateral sepals removed. E. Flower, side view, sepals and petals removed. F. Sepals and petals, adaxial side. G. Ovary, column and tangential section of lip. H. Lip, sagittal section. I. Longitudinal section of spur, showing back-wall with back-wall callus (* symbols show lines and profiles of respected transitional sections). J. Flattened lip, abaxial side. K. Longitudinal section of flattened lip showing front-wall with front-wall calli (+ symbols show lines and profiles of respected transitional sections). L. Column, side view. M. Column, front view. N. Column, half-side view, operculum and pollinarium removed. O. Operculum, view from below, from above, and side view. P. Pollinarium with two pollinia and pollinarium with one pollinium removed. Q. Pollinia, view from front and from rear. All drawn from the holotype specimen Nguyen Van Canh, AL2235 by L. Averyanov.