Begonia sphenantheroides, Peng, Ching-I, Yang, Hsun-An, Kono, Yoshiko, Jung, Ming-Jer & Nguyen, Tien Hiep, 2015

Peng, Ching-I, Yang, Hsun-An, Kono, Yoshiko, Jung, Ming-Jer & Nguyen, Tien Hiep, 2015, Four new species of Begonia (Begoniaceae) from Vietnam: B. abbreviata, B. calciphila, B. sphenantheroides and B. tamdaoensis, Phytotaxa 222 (2), pp. 83-99 : 93-94

3. Begonia sphenantheroides C.-I Peng, sp. nov. (sect. Platycentrum )

( Figs 8 , 9 )

Type: — VIETNAM. Ha Giang Province, Yen Minh District, Du Gia Community, Lung Dam Village , 22°53’59’’N, 105°14’24’’E, elev. 780 m. On rock on N-facing mossy rocky slope above a running stream, semishaded to shaded, moist, mountain slope in broadleaf forest, occasional. Living collection made on 16 Nov 2004 ; type specimens pressed from plants cultivated in experimental greenhouse, Academia Sinica on 13 Sep 2012. Ching-I Peng 20216, with Wai-Chao Leong, Shin-Ming Ku, Nguyen Tien Hiep, Pham Van The & Nguyen Xuan Tam (holotype: HAST 139794 ; isotypes: A, E, HN, MO). ẳžkȁầ

Herbs monoecious, perennial, erect, 50–150 cm tall. Rhizomes congested, 15–25 mm across, to 9 cm long; erect stem stout, 5–20 mm across, internodes 7–30 cm, glabrous. Stipules caducous, triangular or narrowly so, apex aristate or apiculate, margin entire, glabrous. Leaves alternate, petiole to 20–30 cm long, glabrescent (puberulent when young); leaf blade herbaceous, asymmetric, ovate to broadly ovate, 21–41 cm long, 15–28 cm wide, glabrous or subglabrous, base obliquely cordate, margin irregularly loosely serrulate or denticulate; apex acute or short acuminate; venation 7- or 8- palmate. Inflorescences 2–3 (–7)-flowered, protandrous; peduncle 1–5 cm long, scaberulous; bracts deciduous, narrowly ovate to lanceolate, apex acuminate, margin entire, 0.9–1.8 cm long, subglabrous. Staminate flower: pedicel 0.7–1.5 cm long, scabrous; tepals 4, outer 2 reddish, oblong, ovate or orbicular, 0.8–1.9 cm long, 0.5–1.5 cm wide, abaxially scabrous, inner 2 pinkish, broadly oblanceolate to oblong, 0.5–1.7 cm long, 0.3–0.9 cm wide, glabrous; androecium actinomorphic, subglobose, 0.7 cm across, stamens 70–120, yellow, clavate; filaments 0.7–2 mm long, fused to a short central column; anthers 1.5–1.8 mm long, apex truncate. Carpellate flower: pedicel 1.5–2.2 cm long, scabrous; ovary green, unequally 3-winged, wings red, scabrous, 2-locular; placentae axile, bilamellate; tepals 5, reddish, unequal, elliptic to obovate, 0.9–1.8 cm long, 0.5–1.5 cm wide, apex obtuse, abaxially scabrous; styles 2, ca. 5 mm long, 2-cleft, fused at base, stigmatic band wavy-twisted and spiralled. Capsule nodding, unequally 3-winged, abaxial wing falcate, 5–16 mm tall, ca. 7 mm wide, lateral wings triangular or narrowly so, 3–6 mm tall.

Ecology and distribution:— Begonia sphenantheroides C.-I Peng is distributed in limestone areas in Ha Giang Province and Tuyen Quang Province, northeastern Vietnam ( Fig. 3 ). This species grow on semishaded to shady, moist, mossy rocky slopes in broadleafed forest.

Etymology:— The specific epithet refers to its resemblance to some members of Begonia sect. Sphenanthera in bearing stout rhizomes, upright stems and short, axillary, protandrous inflorescences.

Additional specimens examined:— VIETNAM. Tuyen Quang Province, Na Hang Distrct, Xuan Tan Community, Cai village, elev. 124 m, 10 Jan 2007, NQH 316 (HN).

Leaf anatomy and vestiture:— Adaxial surface with glandular trichomes ( Fig. 4G ); cross section ca. 170–200 μm thick, epidermis single-layered on both surfaces, hypodermis absent ( Fig. 4H ); abaxial surface with glandular trichomes, stomata complex single, helicocytic, flat, subsidiary cells (5–)6 ( Fig. 4I ).

Chromosome cytology:— Our study of somatic chromosomes at metaphase of Begonia sphenantheroides revealed 2 n = 22 ( Fig. 5C ), which conforms with the predominant chromosome number in species of sect. Platycentrum . The 22 chromosomes gradually varied in chromosome length from ca. 1.1 to 1.5 μm long. Most chromosomes have centromeres at median, submedian and subterminal positions, however, some chromosomes could not be determined. Satellites were not observed.

Notes:— Begonia sphenantheroides is assignable to section Platycentrum . It bears a superficial resemblance to B. roxburghii A. DC. (section Sphenanthera ) in the erect and branched stems, differing by being monoecious (vs. dioecious) and the broadly ovate leaf blade (vs. triangular-ovate), carpellate flower with 5 tepals (vs. 4 or rarely 3), abaxially scabrous (vs. glabrous) tepals, 2-styled pistil (vs. 4-styled), 2-locular ovary (vs. 4-locular), setose capsule (vs. glabrous or puberulent) and unequally 3-winged (vs. wingless, 4-horned) capsule. Most members of section Platycentrum are rhizomatous or with short aerial stems that appear only at anthesis. Begonia sphenantheroides has upright stems all year-round, a feature not frequently encountered in sect. Platycentrum . In the greenhouse, we observed some abnormally developed tubular pistillate flowers ( Fig. 9 :M) like those of sect. Symbegonia (Warb. 1894: 149) L. L. Forrest & P. M. Hollingsworth (2003: 208) , which was probably induced by the cultivated condition.

Figures

FIGURE 3. Distribution map of Begonia abbreviata (■), B. calciphila (Ì), B. sphenantheroides (●) and B. tamdaoensis (▲) in Vietnam.

FIGURE 4. SEM microphotographs of Begonia leaves. A–C, B. abbreviata; D–F, B. calciphila; G–I, B. sphenantheroides; J–L, B. tamdaoensis; A, D, G, J, Leaf adaxial surfaces; B, E, H, K, Leaf cross-sections; C, F, I, L, Leaf abaxial surfaces. Scale bars = 200 μm.

FIGURE 5. Somatic chromosomes at metaphase of Begonia. A. B. abbreviata (2n = 30: NTH 5917); B. B. calciphila (2n = 30: Peng et al. 20226); C. B. sphenantheroides 2n = 22: Peng et al. 20216); D. B. tamdaoensis (2n = 18: Peng et al. 16638); B’, C’, D’, somatic chromosomes serially arranged by chromosome length and centromere position. Scale bars: B’, C’= 2 μm; D’ = 5 μm. Large arrows indicate a pair of the largest metacentric chromosomes with secondary constrictions (SC) at interstitial regions of the long arms; medium arrows indicate metacentric chromosomes with SC at distal regions of the long arms. Small arrows, large arrowheads and small arrowheads indicate metacentric chromosomes, subtelocentric chromosomes and telocentric chromosomes, respectively.

FIGURE 8. Begonia sphenantheroides C.-I Peng.A, B, Habit; C, Rhizome; D, Staminate flower; E, Carpellate flower; F, F’, Stipules; G, G’, Bracts; H, H’, H’’, Style and stigma; I, Androecium; J, J’, Stamens; K, Capsule; L, Cross section of ovary. All from C.-I Peng et al. 20216 (HAST). Line drawing by Ming-Chao Yu.

FIGURE 9. Begonia sphenantheroides C.-I Peng. A, Habit and habitat; B, Leaf adaxial view; C, Leaf abaxial view; D, Rhizome; E, Inflorescence and staminate flowers; F, Staminate flower, face view; G, Carpellate flower, face view; H, Carpellate flower, side view; I, Stipules; J, Staminate flower, back view, showing indumentum; K, Fruit; L, Cross section of ovary; M, Abnormal sympetalous, tubular flowers seen in cultivation. All from C.-I Peng et al. 20216 (HAST).