Thunbergia impatienoides Suwanph. & S.Vajrodaya, 2018

Suwanphakdee, C. & Vajrodaya, S., 2018, Thunbergia impatienoides (Acanthaceae), a new species from Thailand, Blumea 63 (1), pp. 20-25 : 20-22

Thunbergia impatienoides Suwanph. & S.Vajrodaya , sp. nov. — Fig. 1–4 ; Map 1

Markedly differing from T.fragrans Roxb. by having terete stem with 2-furrows (vs 4-angled), terete petiole with a furrow (vs 4-angled), terete pedicel (vs 4-angled), ovate 5–7 nerved bracteoles (vs cordate 10–12 nerved), involute calyx (vs revolute), magenta to pink (vs white), anther theca rounded (vs mucronate theca),stigma magenta to pink (vs white),pollen smaller (42–44 ± 0.67 vs 54–56 ± 0.67 µm) and reticulate ornamentation on seed surface (vs glabrous with long papillae).

— Type: C. Suwanphakdee 523 ( holo BKF; iso BK, BKF, K, KKU, L, QBG), Thailand, Kanchanaburi, Srisawat, Khao Pu , Salakpra Wildlife Sanctuary Park , 26 Oct. 2016.

Etymology. The specific epithet refers to the gross appearance of its flower which is quite similar to a common ornamental balsam, Impatiens walleriana Hook.f. ( Balsaminaceae ).

Woody twiner with rootstock, scabrous-strigose in almost all parts. Stems several, slender with runners, terete with 2-furrows. Leaves light green; petiole, 0.7–1.0 cm long, with a furrow. Lamina elliptic to elliptic-oblong, 4.0–4.5 by 1.0–2.0 cm, slightly coriaceous, base cordate or slightly hastate, apex acute or mucronate, margin strigose, veins 5–7, palmate arranged. Flower axillary, solitary; salver-form, 3.0–5.0 cm diam, magenta to pink with yellow throat; pedicel: 1.5–2.5 cm long, terete; bracteoles ovate, 1.5–2.0 by 1.0– 1.5 cm, 5–7-nerved, glabrous on adaxial side, base rounded, apex mucronate, margin strigose; calyx: longer than ovary, involute, subequal, 13-toothed, 2.0– 4.0 mm long; corolla tube: slender ventricose, 2.0–3.0 cm long, whitish pale pink, densely glandular hairs outside, glabrous inside; corolla lobe fan-shaped, 2.0–2.5 by 1.5–2.0 cm, slightly overlapped, covered with glandular hairs, abaxial surface slightly hirsute, margin repand; stamens erect, densely glandular hairs at the filamentous base, basal theca rounded; shorter stamens filament c. 3 mm long, anther c. 2 mm long; longer stamens 2–3: filament c. 6 mm, anther c. 2 mm long; disk thin and white; pollen grains in monad, spheroidal, 42–44 ± 0.67 µm diam with spiraperturate aperture. Ovary ovoid with beaked, 2.0–3.0 by 1.0–2.0 mm and forming 4-lobed, style 2.0– 2.5 cm long, stigma bilobed, pink or purplish and exsert at anthesis. Fruit a capsule, hirsute, basal part 1.0–1.2 by 0.7–0.8 cm, beak 1.3–1.5 cm with pedicel 1.5–2.8 cm long, thick upward. Seed globose to subglobose, 3.5–4.0 mm diam, seed coat with regular reticulate ornamentation.

Distribution — Endemic to Thailand (border of northern and western Thailand in Tak province and in western Thailand in Kanchanaburi and Ratchaburi provinces).

Habitat & Ecology — In shaded area in dipterocarp and mixed deciduous forests. Flowering: November to January; fruiting: December to February.

Specimens examined. Tak, 18Jan.1974, C . Phengklai 3156 ( BKF) ; Ratchaburi, Pho Tharam, Khao Tha Kho , 21 Nov. 1985, G . Staples 318 ( BKF) ; Kanchanaburi, Srisawat, Khao Phu, Salakpra wildlife sanctuary, 26 Oct. 2015, C . Suwanphakdee 523 ( type).

Notes — Based on gross morphological characters Thunbergia impatienoides is similar to T. fragrans but differ in having runner stems which is unique. The stem is terete with two furrows (one on each side) and the petiole has a furrow. The flower, which is very showy, is always presented as solitary in the leaf axil. It has an attractive and for Asian Thunbergia unseen pink colour. The distinguishing flower colour characters are dark purple or magenta in flowering bud and turning to pink when mature. The pedicel is rounded and scabrous. The flower is salver-shaped when mature. The corolla lobe is fan-shaped. The five stamens are uniformly didynamous with two shorter and three longer ones. The base of the theca is rounded (usually spurred in Thunbergioideae ). The capsule is hirsute and not glabrous and waxy as in T. fragrans (compared in Table 1 ). The seed of both species are similar but the surface is reticulate in T. impatienoides and long papillate in T. fragrans ( Fig. 3 ). The pollen grains are spheroidal monads. The aperture is spiraperturate which is the common character of Thunbergia . The pollen ornamentation is baculate with fossula. The difference of pollen morphology between T. impatienoides and related species is the size (42–44 ± 0.67 µm vs 54–56 ± 0.68 µm) which significantly supports T. impatienoides to be new to science. The pollen morphological characters of both species are shown ( Fig. 4 ).

Figures

Map 1 Distribution of Thunbergia impatienoides Suwanph. & S.Vajrodaya.

Fig. 1 Thunbergia impatienoides Suwanph. & S.Vajrodaya. a–b. Flower bud; c. flower; d. corolla tube with glandular hairs; e. stamens; f. glandular hairs on filament base; g. anther; h. calyx and ovary; i. style and stigma; j. stigma; k. fruit; l. fruit close-up (C. Suwanphakdee 523 (BK, BKF, K, KKU, L, QBG)). — Photos: C. Suwanphakdee.

Fig. 2 Thunbergia impatienoides Suwanph. & S.Vajrodaya.. Branch with flower; b. cross section of stem; c. part of leaf; mature flower;e–f.bracteole (inside and outside);g.calyx;h.part flower; i. pistil; j. anther; k. fruit (C. Suwanphakdee 523 (BK, BKF, K, KKU, L, QBG)). — Scale bars: a, c–f, i, k = 1 cm; b, g, h, = 2 mm. — Drawn by T. Srisuk.

Fig. 3 Seed morphology of a–c: Thunbergia impatienoides Suwanph. & S.Vajrodaya. a, b. Seed (size and top views); c. reticulate ornamentation on seed surface. — d–f: Thunbergia fragrans Roxb. d, e. Seed (size and top views); f. long papillae on seed surface (a–c: C. Suwanphakdee 523 (BK, BKF, K, KKU, L, QBG); d–f: C. Suwanphakdee 511 (BK, BKF, KKU, QBG)).

Fig. 4 Pollen morphology. a–c: Thunbergia impatienoides Suwanph. & S.Vajrodaya. a. Pollen from light microscope; b. pollen from SEM; c. fossula. — d–f: Thunbergia fragrans Roxb. d. Pollen from light microscope; e. pollen from SEM; f. fossula (a–c: C. Suwanphakdee 523 (BK, BKF, K, KKU, L, QBG); d–f: C. Suwanphakdee 511 (BK, BKF, KKU, QBG)).