Loxostigma puhoatense N.D. Do, N.S. Ly, D.H. Nguyen & T.H. Le, 2020

Ly, Ng ọc-Sam, Nguy ễn, Danh-Hung, Le, Th ị-Hương, Tr ần, Minh-H ợi, Đ ỗ, Ng ọc-Đai, Trương, Ba-Vương & Maciejewski, Stephen, 2020, Loxostigma puhoatense (Gesneriaceae), a new species from North Central Vietnam, PhytoKeys 151, pp. 49-57 : 49

Loxostigma puhoatense N.D. Do, N.S. Ly, D.H. Nguyen & T.H. Le sp. nov. Figs 1 , 2

Diagnosis.

This species is most similar to L. dongxingensis and L. damingshanensis in the plant habit, indumentum system of stem, leaves, shape of leaf blades, calyx and pistil but differs from the latter two in the leaf blade with abaxially reddish-purple and number of lateral veins, longer peduncle, shorter white to pale yellowish-white corolla with purple-spotted inside, longer abaxially stamens that are lower adnate above corolla tube base, shorter and glandular-puberulent ovary, and sparsely glandular-puberulent style.

Type:

Vietnam. Nghe An Province: Tien Phong Commune, Na Chang Village, Pu Hoat NP, 19°46'06"N, 109°55'08"E, atl. 781 m, 04 October 2018, Do Ngoc Dai, Nguyen Danh Hung, Le Thi Huong, DHH 1021 (holotype: VNM, isotype: P).

Description.

Epiphyte, evergreen, perennial herbs with rhizomes. Rhizome internodes up to 20 cm long, 3.5-4 mm in diam. Stem simple, borne from a node of the rhizome, shallow angular at the middle internodes, terete toward both ends, 28.5-55 cm long, 3.5-7 mm in diam., pale green, somewhat pubescent. Leaves opposite, spread along stem, unequal in a pair; petiole cylindrical, adaxially sunken, greenish to purplish, abaxially rounded and greenish, 1-3.3 cm long, 3-6 mm in diam., pubescent; leaf blade broadly elliptic to elliptic-ovate, chartaceous when dried, 4.2-25.5 × 3-15.5 cm [11.3-25.5 × 8.9-15.5 cm in larger leaves, 4.2-9.3 × 3-6.2 cm in smaller leave], adaxially light green, abaxially reddish purple, sparsely pubescent on both surface, pubescent on the midrib and lateral veins of the abaxial surface, lateral veins 11-19 pairs, base usually oblique, subcordate, margin serrate to indistinctly denticulate, apex acuminate. Cymes axillary, subterminal, 2-3-branched, 3-25-flowered; peduncle 9.2-17.5 cm long, 2-3 mm in diam., pale greenish, densely pubescent and glandular-pubescent. Bracts ovate to oblong-ovate, pale greenish-white tinted, 5-8.5 × 2.8-3.5 mm, adaxially glabrous, abaxially densely pubescent and glandular-pubescent, margin somewhat denticulate. Pedicel 1.1-1.4 cm long, ca. 1.5 mm in diam., greenish-white, densely pubescent and glandular-pubescent. Calyx 5-sect from the base, segments equal, whitish, narrowly ovate, 6-7 × 2-2.5 mm, adaxially glabrous, abaxially densely pubescent and glandular-pubescent, margin entire, apex acute. Corolla somewhat campanulate, white to pale yellowish-white, gibbous abaxially, with purple spots inside, 3.7-3.8 cm long, outside densely glandular-pubescent, inside glabrous; corolla tube 2.7-2.9 × 1.4-1.6 cm; corolla limb distinctly 2-lipped, adaxial lip 5-6 mm long, 2-lobed, lobes semi-orbicular, 5-5.5 × 7-7.5 mm, deflexed, apex rounded; abaxial lip3-lobed, 10-11 mm long, lobes semi-orbicular, 4-5.5 × 4-5 mm, deflexed, apex rounded. Stamens 4, adaxial stamens adnate to 7-8 mm above corolla tube base, 15-16 mm long, abaxial ones adnate to 6-7 mm above corolla tube base, 20-21 mm long; filaments linear, white, glabrous, slightly curved; anthers sub-globose, theca coherent apically in pairs, pale cream; staminode one, adnate to 7-8 mm above corolla tube base, ca. 2 mm long. Disc ring-like, subentire, ca. 2.5mm high. Pistil 2.2-2.4 cm long; ovary oblong, greenish, 10-12 × 1.8-2 mm, densely glandular-puberulent; style linear, pale greenish, 9-10 × ca. 1 mm, sparsely glandular-puberulent; stigma 2, equal, 2-lipped, undivided. Capsule 6-6.5 cm long, 2-3mm in diam., oblong-linear, straight, not twisted, glabrous, blackish-brown, dehiscing loculicidally to base, valves 2. Seeds linear, 2-2.5 mm long, brown, with appendages on both ends of the seeds; appendages 2.5-3 mm long.

Distribution and habitat.

Loxostigma puhoatense is currently known from a single population with eight mature plants, in tropical evergreen broad-leaf forests, Pu Hoat Nature Reserve, Nghe An Province. More data is needed to determine conservation status. It is an epiphytic plant (Fig. 2A ), growing on the surface of Ficus sp. (Moracaeae), and is associated with fern (e.g. Asplenium nidus L. ( Aspleniaceae ), epiphytic herbs (e.g. Aeschynanthus acuminatus Wall. ex A. DC. ( Gesneriaceae ), Pothos chinensis (Raf.) Merr. ( Araceae ) and is dominated by Beilschmiedia ferruginea H.Liu, Cinnamomum polyadelphum (Lour.) Kosterm., C. tamala (Buch.-Ham.) T.Nees & Eberm., Lithocarpus balansae (Drake) A. Camus, Syzygium grande (Wight) Walp., S. odoratum (Lour.) DC., Gordonia axillaris (Roxb. ex Ker Gawl.) Endl …

Phenology.

Flowering in October-December and fruiting November-February.

Etymology.

The specific epithet " puhoatense " is derived from the type locality.

Other specimens examined (Paratypes).

Vietnam. Nghe An Province: Pu Hoat NP, 24 February 2019, 19°46'06"N, 109°55'07"E, Do Ngoc Dai, Nguyen Danh Hung, Nguyen Thi Huong, DHH 1162 (VNM).

Vernacular name.

Vietnamese language: Xuyến thư pù hoạt

Taxonomic notes.

Loxostigma puhoatense is morphologically similar to L. dongxingensis and L. damingshanensis in the plant habit, somewhat pubescent stem, elliptic to ovate leaf lades, narrowly ovate calyx with margin entire, the same shape of flower. However, the new species differs from both of them in the abaxially reddish-purple leaf blade with pubescent along veins (vs green, villous of L. dongxingensis and pilose of L. damingshanensis ), lateral veins 11-19 pairs (vs. 6-10 pairs and 5-10 pairs of the latter two, respectively), shorter white to pale yellowish-white corolla (3.7-3.8 cm long) with purple-spotted and glabrous inside (vs. 4-5 cm long, yellow, inside spotted or not and sparsely pubescent only on lobes of adaxial lip of L. dongxingensis , and 4.8-6 cm long, yellow, inside purple stripes and sparsely pubescent only on lobes of abaxial lip, of L. damingshanensis ), longer abaxial stamens in 2-2.1 cm long (vs. ca. 18 cm and ca. 14 cm in the latter two, respectively), shorter and densely glandular-puberulent ovary in 1-1.2 cm long (vs. ca. 2 cm, glabrous of L. dongxingensis and ca.1.8 cm, densely glandular-pubescent of L. damingshanensis ), and sparsely glandular-puberulent style (vs. glandular-pubescent of L. dongxingensis and L. damingshanensis ). The staminode of L. puhoatense is ca. 2 mm long (vs. ca. 1 mm of L. dongxingensis and ca. 1.5 mm of L. damingshanensis ) and adnate above corolla tube base in 0.7-0.8 mm long (vs. ca. 1.3 cm of L. dongxingensis and ca. 1.8 cm of L. damingshanensis ). Furthermore, the densely pilose petiole of L. dongxingensis is distinguished with the somewhat pubescent petiole of L. puhoatense and L. damingshanensis . The unbranched cyme and inconspicuous or absent of bract of L. damingshanensis are distinct with the branched cyme and 2- somewhat ovate bracts of the remained two. A detailed morphological comparison between L. puhoatense , L. dongxingensis , and L. damingshanensis is provided in Table 1 .

Figures

Figure 1. Loxostigma puhoatense (from the holotype). A mature plant with flowers B a part of stem C inflorescence D dorsal view of flower E opened flower showing stamens F gynoeciums G detail of stigma (from dry specimen) H infructescence I seeds. Drawn by Ba-Vuong Truong from Do Ngoc Dai, Nguyen Danh Hung, Le Thi Huong, DHH 1021.

Figure 2. Loxostigma puhoatense. A plant in natural habitat B apical part of flowering plant showing inflorescences (with flowers and young fruits) and leaves C inflorescence D abaxial leaf E adaxial leaf F flower (from below) G flower (top view) H flower (front view) I longitudinal section with upper lip removed J stamens with gynoecium and calyxes K dried fruits. Photos by Ngoc-Dai Do, plate by Ngoc-Sam Ly.