Curcuma (Ecomatae) rubroaurantiaca Skornick . & Soonthornk., 2023

Leong-Skornickova, Jana, Soonthornkalump, Sutthinut, Lindstroem, Anders Jan, Niwesrat, Sira, Lim, Sarah Qing & Suksathan, Piyakaset, 2023, Curcuma maxwellii and C. rubroaurantiaca (Zingiberaceae, Zingiberoideae), two new species from Thailand, PhytoKeys 235, pp. 237-248 : 237

Curcuma (Ecomatae) rubroaurantiaca Skornick. & Soonthornk. sp. nov.

Fig. 4

Diagnosis.

Similar to Curcuma maxwellii by general habit and flower colour, but differs by leaf blades abaxially densely puberulent (vs. glabrous), inflorescence composed of up to 14 fertile bracts (vs. inflorescences composed of 15-34 bracts), bracteoles absent (vs. small bracteoles present), larger stamen 19-22 mm long (vs. 16-18 mm long), anther 16-17 mm long with flattened spurs, prominent anther crest 2-3 mm long with central longitudinal groove and anther thecae forming narrowly rhomboid shape (vs. anther 13-14 mm long with conical spurs, thick anther crest ca. 1 mm long without central longitudinal groove and anther thecae forming narrowly obovate shape).

Type.

Thailand, Sakon Nakhon Province, Phanna Nikhom District, Na Hua Bo subdistrict, ca. 200 m a.s.l., 15 July 2023, Soonthornkalump Sutt-242 (Holotype: BKF! (including flowers in spirit as part of a single preparation); Isotype: SING! (including flowers in spirit as part of a single preparation)). Fig. 4 .

Description.

Rhizomatous herb to 0.6 m tall. Rhizome branched, main rhizome ovoid to obvoid, 1.5-2 × 1-2 cm, branches 1-4 cm long, up to 1.2 cm diam., cream-white to ochraceous externally, cream-white internally, slightly aromatic; root tubers globose to fusiform 2-4 × 1-2 cm. Leafy shoot with 2-5 leaves when flowering; pseudostem to ca. 20 cm long, composed of leaf sheaths; bladeless sheaths ca. 3-4, cream-white at base, tinged with rich brownish-red to red distally, fully decayed at anthesis; leaf sheaths brownish-red at base, gradually more green with reddish tinge, densely puberulent to puberulent; ligule 3-4 mm long, bilobed, lobes rounded to obtuse, brownish-red, densely puberulent; petiole (11-)18-30(-45) cm long (petiole of first leaf shortest, innermost leaves longer), canaliculate, green with brownish-red tinge (rarely plain green in distal part), puberulent to densely puberulent, less so in the groove; leaf blade broadly elliptic to elliptic-ovate, (12.5-)19-40 × (5-)9-17 cm, prominently plicate, adaxially green, pubescent on main raised veins, near mid-rib and margins, sometimes throughout entire leaf blade, abaxially lighter green, densely puberulent, mid-rib green, puberulent on both sides, base cordate, often slightly oblique, apex acute to acuminate. Inflorescence central, breaking through the pseudostem, many-flowered; peduncle to 7 mm diam., embedded within pseudostem; thyrse 4-8.5 cm long, 3-6 cm diam. in the middle, without coma; fertile bracts to 14 per inflorescence, 2-5 × 1-3.6 cm (largest at the base of the inflorescence), ovate to trullate with acute apex, gradually smaller and more ovate towards the apex, margin curved inwards, various colours from white to bright red, shortly puberulent to pubescent on both sides (longer, but sparser hair on the inside), connate in the lower 1/3 to 1/4, enclosing cincinnus with 4 flowers at the base of the inflorescence, the number of flowers per bract gradually decreasing to 2 or 1 upwards; bracteoles absent. Flowers (5-)6-7.4 cm long, much exserted from the bracts; calyx to 24 mm long, 3-toothed, unilaterally split 8-12 mm, semi-translucent with pink-red tinge, pubescent; floral tube (30-)40-48 mm long, externally white to pale yellow at the base, gradually with red tinge distally, sparsely shortly pubescent in the middle third, otherwise glabrous, internally pale yellow at the base, bright yellowish-orange distally, mostly glabrous, but pubescent at the point where the tube widens, with dorsally placed groove holding the style; dorsal corolla lobe 20-27 × 6-8 mm, triangular elliptic-oblong, with sides rolled inwards, red outside, light red to pale orange inside, glabrous on both sides, apex mucronate, mucro 2-3 mm, with a few sparse hairs; lateral corolla lobes 22-25 × 5-8 mm, triangular elliptic with hooded blunt apex, glabrous, red outside, light red to pale orange inside; labellum (20-)24-26 × 13-17 mm, 7-9 mm broad at basal 1/3, then bluntly rhomboid in distal 2/3, 13-17 mm at widest point, apex bifid with an incision 5-8 mm long, yellowish-orange, median band thick with central groove, darker orange, sides of the lamina yellow-orange, glabrous and shiny on both sides; lateral staminodes 20-22 × 11-13 mm, unequally bluntly rhomboid, bright orange, with pale reddish tinge at base, glabrous and somewhat shiny on both surfaces. Stamen ca. 19-22 mm long; filament 7-10 mm long, 3.5-4 mm broad at base, 1.5-2 mm broad at apex (the point of attachment to the connective), orange, sparsely covered with glandular hairs; anther 16-17 mm long, spurred, connective yellowish-orange, densely covered with short glandular hairs (especially dorsally, less so on the sides); anther spurs 2-3 mm long, triangular and flattened with sharp tips pointing outwards; anther crest thick ovate to oblong with rounded apex and central longitudinal groove, 1.5-3 mm long and 1.8-2 mm at base, darker orange; anther thecae 9-11 mm long, forming very narrowly rhomboid shape, dehiscing along their whole length, connective tissue at the base of the thecae forming blunt knob protruding forward; pollen white. Epigynous glands 2, 6-9 mm long, 0.5-1 mm in diam., apex acute, cream at base, yellowish distally. Style thin, white, glabrous, held in groove in dorsal side of floral tube; stigma ca. 1 mm long, 1-1.5 mm wide, cream to yellowish, ostiole ciliate, facing upwards. Ovary 2.5-3.5 × 2-2.5 mm, trilocular, cream, pubescent, hairs ca. 1 mm long. Fruit and seeds not seen.

Habitat and phenology.

Growing in semi-shade and edges of evergreen forest mixed with bamboo, in moist places, at 200-800 m a.s.l., on sandstone as well as limestone bedrocks. The species flowers from July till September, with fruiting presumably extending into November.

Distribution.

Known to occur in Loei, Sakon Nakhon, (NE Thailand), Chayaphum (E Thailand) and Phetchabun Provinces (N Thailand).

Etymology.

The specific epithet refers to its bright red and orange flowers.

Vernacular name and uses.

Similarly to the previous species, the vernacular name Wan Pet Ma (ว่านเพชรม้า) is used also on this species; we, therefore, propose refining the vernacular name to Wan Pet Ma Isan (ว่านเพชรม้าอีสาน) for this species. No uses were reported, but the species has a good potential as an ornamental plant.

Provisional IUCN conservation assessment.

In addition to our collection, we have found an additional two herbarium collections from Loei Province (Phu Luang), two collections from Chayaphum Province (Chulabhorn Dam and Phu Kiew) and two specimens from Petchabun, which could be confidently assigned to this species. Most of these areas are in National Parks under legal protection. The species was also sighted by us in an additional two legally-protected areas, namely Phu Pha Lom Forest Park (Loei Province) and Phu Phan National Park (Sakon Nakhon Province). We, therefore, propose to treat this species as Least Concern (LC).

Specimens examined.

Paratypes: Thailand, Loei Province, Phu Luang, s.d., Bunchuai, K. s.n. (BKF); Phu Luang, 1 September 1966, Phusomsaeng, S. 26 (BKF); Mueang District , Wang Kan subdistrict, 13 October 2022, Soonthornkalump, S. Sutt 243 (QBG, including flowers in spirit as part of a single specimen) .

Notes.

Amongst the orange-red flowered species from this alliance in Thailand, this species is easy to recognise by its anther with well-developed and sometimes slightly recurved anther crest (observed, in particular, in populations in Loei), and thecae forming very narrowly rhomboid shape. This species can be recognised from C. stenochila by densely puberulent leaf blades and by the shape of the labellum, which does not have a narrow basal claw as in C. stenochila .

Figures

Figure 4. Curcuma rubroaurantiaca Skornick. & Soonthornk. at the type locality A habit B inflorescence with detail of flower in front view C detail of leaf sheaths and ligules D rhizome E inflorescence with detail of flower in side view F two flowers and dissected flower (from left: ovary with epigynous glands, calyx, floral tube (dissected longitudinally), upper row dorsal and lateral corolla lobes and stamen, lower row lateral staminodes and labellum G stamen from front, back and side view. All from the type collection, Soonthornkalump Sutt- 242. Photographed by Sutthinut Soonthornkalump.