Bulbophyllum viridipallidum, 2023

Nguyen, Van Canh, Averyanov, Leonid V., Maisak, Tatiana V., Nguyen, Thi Lien Thuong, Nguyen, Van Khuong, Pham, Thi Thanh Dat, Nguyen, Danh Duc, Dang, Van Son, Aromyen, Warapong & Truong, Ba Vuong, 2023, The review of Bulbophyllum section Tripudianthes (Orchidaceae) in the flora of Vietnam with the description of new species, B. viridipallidum, Phytotaxa 598 (1), pp. 59-68 : 61-66

3. B. viridipallidum Vuong, Aver. & V.C.Nguyen sp. nov.

( Fig. 2 ).

Type:— VIETNAM. Kon Tum Province, Dak Ha District, Dak Psi Commune, Dak Trua Forest , epiphyte on tall trees, 16 February 2023 , Truong Ba Vuong, BV 1688 ( holotype VNM00043087 !) .

Etymology: —the specific epithet refers to the pale greenish yellow lateral sepals, a character common with related species.

Description:—Herb perennial, epiphytic. Pseudobulbs densely clustering, ovoid to broadly ovoid, sometime slightly compress, 7–16 mm long, 5–17 mm in diameter, 2-leaved. Leaves deciduous, plant leafless at anthesis. Inflorescence from base of pseudobulbs; peduncle greenish-yellow, 39 – 40 cm long, at base with 2 scarious, brownish overlapping tubular bracts, above with 2 similar bracts; rachis pendulous, 3.5 – 4 cm long, bearing 6 simultaneously opening flowers; floral bract triangular, brown 1.7–2 mm long, acute; pedicel and ovary 2.5–3 mm long, pedicel terete shorter than conoid ovary. Flowers odorless, lateral sepals pale greenish yellow; median sepal and petals pale reddish brown, lip white speckled with pink or pink purple, callus yellow, with many pink dots at apex dark purple. Median sepal ovate to broadly ovate, ca. 5.5 mm long, ca. 3 mm wide, acuminate to attenuate, adaxially in middle with 2 prominent keels, in apical half sparsely hairy with stiff hairs. Lateral sepals obliquely oblong lanceolate, ca. 4 cm long, ca. 0.3 cm wide, acute, twisted at base, lower margin free at base, connate to the tip, adaxial surface sparsely hairy with short stiff hairs. Petals obliquely triangular, glabrous, 4–4.5 mm long, 1–1.5 mm wide, margin fimbriate, acuminate to attenuate. Lip simple, oblong in outline, 3–3.2 mm long, 1–1.5 mm wide, movably adnate to column foot by small ligament, apex rounded; margins in basal half erect, finely papillose, apical half fimbriate along the margin; adaxial surface at base with 2 rounded longitudinal calli fused distally into a single prominent central longitudinal keel inflated at the lip apex turn into prominent half-ovoid callus; abaxial sparely pillose. Column ca. 1.5 mm long, at front with inconspicuous rounded wings; column foot 2–2.5 cm long, forward directed, straight; stelidia subulate, ca. 1 mm long, slightly curved; stigma half circular, concave, ca. 1 mm across; rostelum non protruding; anther cap helmet shaped, ca. 1 mm long, apex with a gibbose densely papillose inflation; pollinia 4, bright yellow, half ovoid, inner smaller than outer. Fruits not seen.

Habitat and phenology: —Epiphyte on tall trees in evergreen broad-leaved forest. Flowering observed during February.

Distribution: — VIETNAM (Kon Tum Province, Dak Ha District). Endemic.

Proposed conservation status:—According to currently available data, the new species is very rare and found only from one location. More field studies are required for preparing its conservation assessment. In view of gaps in data and in accordance with IUCN criteria ( IUCN, 2022), the species should be assessed as Data Deficient (DD).

Notes:—The new species in its entire median sepal is similar B. kanburiense and B. khaoyaiense . It also similar with B. wallichii in two prominent calli placed on the lip base. The dorsal sepal and flower comparison is presented on Fig. 3 . The morphological differences of the new species and morphologically similar species are presented in the table.

Data of B. wallichii based on BV 1484 (VNM00043086), BV 1483 (LE01123508 & LE01169312); data of B. kanburiense based on Seidenfaden (1970: 344); data of B. khaoyaiense based on Seidenfaden & Smitinand (1965: 795) and Seidenfaden (1970: 342).

Figures

FIGURE 2. Bulbophyllum viridipallidium Vuong, Aver. & V. C. Nguyen, sp. nov. A. Flowering plant. B. intact inflorescence. C. Portion of inflorescence. D. Floral bract. E. Base of flower, with median sepal, view from above. F. Intact flowers, view from above and from below. G. Median sepal, abaxial side, adaxial side, and side view. H. Lateral sepals, abaxial and adaxial side. I. Petals, abaxial and adaxial side. J. Lip, view from different sides. K. Ovary, column and lip, side view. L. Ovary, column and column foot, side view. M. Column apex, side and frontal view. N. Anther cap, view from different sides. O. Pollinaria, view from different sides. All photos by Truong Ba Vuong from type specimen BV 1688, photo correction and design by L. Averyanov and T. Maisak.

FIGURE 3. Flower and dorsal sepal comparison between: A & B. Bulbophyllum khaoyaiense. C. & D. B. kanburiense. E. & F. B. refractum. G. & H. B. tripudians (photo by Warapong Aromyen from Thailand).