Parahellenia trongduyii Juan Chen, V.C.Nguyen, K.S.Nguyen & N.H.Xia, 2023

Chen, Juan, Nguyen, Van Canh, Nguyen, Van Khuong, Nguyen, Khang Sinh, Nuraliev, Maxim S. & Xia, Nianhe, 2023, Taxonomic studies on Parahellenia (Costaceae) in Vietnam: a new species, P. trongduyii, and a new combination, P. candida, Phytotaxa 583 (1), pp. 72-80 : 73-79

Parahellenia trongduyii Juan Chen, V.C.Nguyen, K.S.Nguyen & N.H.Xia , sp. nov.

Diagnosis:—It is similar to P. tonkinensis , but differs in unbranched or barely branched (vs. densely branched) stems, narrowly triangularlanceolate (vs. broadly triangular) and glabrous (vs. densely pubescent) axillary buds, softly mucronate (vs. pungent, making a finger bleeding if touched) bract apex, yellow to whitish yellow labellum with longitudinal orange to red lines at center (vs. yellow labellum with longitudinal red lines at center), anther crest 9‒12 mm (vs. 3‒5 mm) long and slightly bilobed (vs. deeply bilobed) dorsal appendage of stigma.

Type:— Collected from the material cultivated at V. C. Nguyen’s private garden on 25 August 2021, V. C. Nguyen & V. K. Nguyen CD 01 (holotype HN; isotypes HN, IBSC). Originally collected by T. D. Nguyen in July 2019 from Vietnam, Dak Lak Province, Krong Bong District, Chu Yang Sin National Park , Yang Mao Commune , along banks of small streams at elevations of 700‒900 m a.s.l. ( Figs. 1‒3 ) .

Terrestrial evergreen perennial herb. Rhizome plagiotropic, tuberous, 2‒4 cm in diam., brown externally, white internally, glabrous. Leafy shoot 75‒140(‒250) cm tall, up to 3 cm in diam. at base. Stem more or less straight, erect to suberect, unbranched or barely branched at higher nodes. Axillary bud 1 at each node, narrowly triangular-lanceolate, 12‒15 × 5‒6 mm, green with red tip, glabrous. Bladeless sheaths closed, reddish brown, membranous, caducous, glabrous. Leaves 10‒20, consistently clustered toward the shoot apex; sheaths closed, pale green when young, later becoming reddish brown, glabrous; ligule 1.8‒2.5 mm long, glabrous, upper margin minutely fimbriate; petiole 0.9‒2.2 cm long, 0.8‒1 cm in diam., adaxially grooved, yellowish green, reddish brown at base, glabrous; blades 20‒35 × 5‒8 cm, the lowest ones obovate to oblanceolate, the upper ones oblanceolate to elliptic, base narrowly attenuate, apex acuminate, adaxial surface deep green, abaxial surface pale green, glabrous on both sides, midvein slight sunken adaxially and conspicuously raised abaxially. Inflorescence arising directly from the rhizome, 20‒25 cm long (including peduncle and bracts only), lax; peduncle horizontal to ascending, terete, 4‒6 cm long, 1.4‒1.6 cm in diam., bearing 4‒6 sheaths, sheaths tubular, coriaceous, reddish brown, glabrous; spike 16‒20 × 6‒9 cm, narrowly ellipsoid or nearly cylindrical; secondary peduncle very short, glabrous; bracts 4‒5 × 2‒2.5 cm, the lowest bracts broadly elliptic, the upper ones elliptic, cucullate, apex softly mucronate (not pungent), coriaceous, pale brown to reddish brown, glabrous, each subtending 1 flower with 1 bracteole; bracteoles 2.5‒2.8 × 0.7‒0.9 cm, narrowly lanceolate, apex acuminate to spiny (but not pungent), coriaceous, pale brown to reddish brown, glabrous. Flowers 8.5‒10 cm long; calyx 3.2‒4 cm long, coriaceous, pale green when young, becoming reddish brown when old, glabrous, tube 2.5‒3.3 cm long, 7‒9 mm in diam., lobes 3, 0.7‒1 × 0.6‒0.7 cm, broadly ovate, slightly involute, apex softly mucronate, pale green with reddish brown apex when young, becoming reddish brown when old; floral tube (from apex of ovary to base of divergence of corolla lobes) 2.2‒2.5 cm long, 0.3‒0.5 cm in diam., fused with style in basal 1.6 cm, white, glabrous externally; corolla lobes 4.3‒5 × 1.9‒2.2 cm, obovate, white, glabrous; staminal tube (from the point of divergence of corolla lobes to base of divergence of labellum and stamen) 1.4‒1.7 cm long, yellow, with dense yellow hairs internally, pubescent externally; labellum 6.5‒7.5 × 5.5‒6.5 cm, flabellate after full expansion, yellow to whitish yellow with longitudinal orange to red lines at center, covered with glutinous papillae at center and base, margin rugose and pubescent; stamen 3.2‒3.6 cm long (when crest flattened), 0.6‒1 cm wide, petaloid, oblong, yellow, adaxially concave, glabrous, abaxially slightly convex and thickened, with sparse long glandular hair; anther crest 0.9‒1.2 cm long, 5.5‒6.2 mm wide, oblong, strongly recurved to revolute on abaxial side, yellow with longitudinal red lines at adaxial side, broadly acute to obtuse at apex, margin pubescent; thecae 0.9‒1 cm long, 1.8‒2.4 mm wide in the middle, slightly broadening towards ends. Ovary inferior, 1.1‒1.4 cm long, 5‒6 mm in diam., glabrous, trilocular with axile placentation and apically embedded beige-coloured gynopleural nectaries, each locule with numerous ovules; style 4.5‒4.8 cm long (free part), glabrous; stigma 1.7‒1.8 mm long, 2.8‒3.3 mm wide, semi-circular, flattened, 2-lobed, lobes overlapping, white, margin ciliate, dorsal appendage slightly bilobed, white. Infructescence of almost the same size as inflorescence, often continuously formed (with fruits at base when flowers still anthetic at apex), with persistent bracts and bracteoles. Fruits 1.8‒2.2 cm long, 1.1‒1.2 cm in diam., nearly ellipsoid, reddish brown, glabrous, with persistent calyces. Seeds 3‒4 × 2‒2.3 mm, irregularly barrel-shaped, black, aril basal and not enclosing the seed, white.

Phenology:—Flowering from June to August; fruiting from July and likely continuing till October.

Etymology:—The specific epithet is named after Mr. Nguyen Trong Duy, who collected the living material of the species in its type locality.

Suggested common names:—Mía dò Trọng Duy (Vietnamese), Øṃṁƛąae (duō lè dì wō sŭn huā) (Chinese).

Distribution, habitat and conservation:—This species is currently known from Chu Yang Sin National Park in Dak Lak Province and Thach Nham protected forest in Kon Tum Province in Vietnam. Parahellenia trongduyii grows in shady, moist places along small streams, in evergreen broad-leaved forests at elevations of 700–900 m a.s.l. We observed five clumps of the species in Chu Yang Sin National Park, a protected area where agricultural activities and exploitation of non-timber forest products are prohibited. Due to lack of information on the distribution (extent of occurrence (EOO) or areas of occupancy (AOO)) and population size of P. trongduyii , its conservation status is assessed here as Data Deficient (DD), following the IUCN Red List Categories and Criteria ( IUCN 2012).

Notes:—As elaborated in the diagnosis, Parahellenia trongduyii closely resembles P. tonkinensis but is readily distinguished from it in the field even by vegetative characters, e.g., barely branched leafy shoots and narrowly triangular-lanceolate glabrous buds.

Parahellenia trongduyii is also similar to P. candida , but differs in reddish brown (vs. brown) and glabrous (vs. densely puberulent) bladeless sheaths, glabrous (vs. puberulous) abaxial side of leaf blade, softly (vs. sharply) mucronate bract apex and yellow (vs. white) flowers. A detailed comparison is provided in Table 1 .

Additional specimen examined (paratype):— VIETNAM. Kon Tum Province: Kon Plong District, Thach Nham protected forest, 17 km N of Mang Den Town , near river, 14°45’26’’N 108°18’35’’E, 900 m, 8 June 2016, M. S. Nuraliev 1673 ( MW: MW0753815 ) ( Fig. 4 ) .

Figures

FIGURE 1. Parahellenia trongduyii. A. Rhizome with a terminal bud. B. Leafy shoot. C. Nodes with leaf bases. D. Node with an axillary bud. E. Inflorescence with flowers. F. Bract, bracteole, ovary and calyx. G. Flower. H. Flower (calyx, corolla lobes and labellum removed). I. Longitudinal section of a flower. J. Corolla lobes (abaxial and adaxial views). K. Stamen and labellum. L. Longitudinal sections of a fruit. M. Stamen (abaxial and adaxial views). N. Stamen (lateral view). O. Stigma (from left to right: lateral view, abaxial view and adaxial view). Drawn by Mr. D.H. Cui from the type V.C. Nguyen & V.K. Nguyen CD 01.

FIGURE 2. Parahellenia trongduyii: vegetative morphology. A, B. Habit. C. Rhizome and leafy shoot. D, E. Nodes with leaf sheaths and petioles. F. Node with bud. G. Rhizome and a terminal bud. Photos by V.C. Nguyen from the type V.C. Nguyen & V.K. Nguyen CD 01.

FIGURE 3. Parahellenia trongduyii: floral morphology. A. Inflorescences with flowers. B. Inflorescence (lateral view). C. Flower dissection. D. Flower (longitudinal section) showing floral tube fused more than halfway with the style base. E. Stamen (from left to right: abaxial view, adaxial view and lateral view). F. Stigma (from left to right: lateral view, abaxial view and adaxial view). G. From left to right: a fruit with bract, bracteole and calyx, and a fruit (longitudinally dissected) showing seeds. Photos by V.C. Nguyen from the type V.C. Nguyen & V.K. Nguyen CD 01.

FIGURE 4. Parahellenia trongduyii. A. Habit. B, C. Inflorescences. D. Flower (top view). E. Flower (front view). F. Flower (lateral view). G. Stamen and style (lateral view). Photos by M.S. Nuraliev from Nuraliev 1673.