Strobilanthes phengklaii Kladwong & Chantar., 2024

Kladwong, Pornchai & Chantaranothai, Pranom, 2024, Notes on Strobilanthes (Acanthaceae) with capitate inflorescences in Thailand, PhytoKeys 244, pp. 89-126 : 89-126

18. Strobilanthes phengklaii Kladwong & Chantar. sp. nov.

Figs 6 , 7 , 11 B

Type.

Thailand, Chaiyaphum, Phu Khieo WS, Oct 1999, Phengklai et al. 12261 (holotype BKF [ SN 127785 !]; isotypes BKF [ SN 143321 !, SN 127784 !]) .

Diagnosis.

Similar to S. brandisii T. Anderson and S. esquirolii H. Lév. in having single capitate inflorescences, sessile or subsessile and densely white sericeous bracts but differs in having lanceolate or linear-lanceolate bracts and yellow corolla vs. spathulate bracts and purple corolla in S. brandisii and oblong-lanceolate bracts and violet corolla in S. esquirolii . The morphological difference among S. brandisii , S. esquirolii and S. phengklaii are presented in Table 2 .

Description.

Herbs up to 40 cm tall, perennial, erect or decumbent, anisophyllous. Stems 4 - angled, sulcate or subterete when mature, pubescent or glabrescent. Leaves petiolate; blades lanceolate to oblong-lanceolate, 1.8–10 × 0.6–3.5 cm, hairy on adaxial surface, pubescent on abaxial surface, lateral veins 3–7 pairs, prominent on both surfaces, apex attenuate to caudate, base attenuate, and decurrent onto petiole, margin serrate or crenate, ciliate; petiole 0.3–2.5 cm long, pubescent. Inflorescences terminal capitate, 3–5 - flowered; peduncle absent; bracts lanceolate or linear-lanceolate, 5–13 × 2–4 mm, persistent, the outer one longer than the inner, white sericeous on both surfaces, the upper part sparsely hispid, apex obtuse, margin entire or obscurely serrate, base sessile, ciliate; bracteoles linear, 3–5 × ca. 0.8 mm, white sericeous on both surfaces. Calyx 5 - lobed; lobes linear, 4–5 × 0.5 mm, subequal, apex acute, white sericeous on both surfaces. Corolla yellow, funnel shaped, 2–4 cm long, densely white sericeous on top at bud, sparsely pubescent at anthesis, glabrous inside except hairs retaining style; tube yellow, cylindric for 4–6 mm long; mouth 1–1.5 cm wide; lobes 5, ovate, 3–4.5 × 3.5–5 mm, apex obtuse. Stamens 4, included, didynamous; short filaments 2 mm long, long filament 3–5 mm long, all filament straight and glabrous; anther thecae ca. 1.5 mm long, white, without spur; pollen 3 - colporate, prolate or subprolate in equatorial view, circular in polar view, polar range 51–67 μm, equatorial range 31–41 μm; ectoapertures fusiform; exine divided into longitudinal ribs, each rib with a coarse ladder-like reticulum. Ovary ellipsoid, 2 mm long, densely white sericeous at apex; style 2.5–3 cm long, puberulous. Capsule fusiform, 5–7 × 3–4 mm, white sericeous, 4 - seeded. Seeds ovate in outline, ca. 1.8 × ca. 1.5 mm, hairy.

Distribution.

Endemic to Thailand.

Ecology.

Common in shaded areas in dry evergreen forest; ca. 600 m alt., flowering and fruiting from October to December.

Etymology.

Named in honour of Dr Chamlong Phengklai, a senior botanist at the Forest Herbarium ( BKF) who collected the type specimens of S. phengklaii .

Additional specimens examined

(paratypes): Thailand, North-eastern: Loei, Phu Luang WS, from Ban Na Luang to north ride ca. 600 m alt., 3 Dec 1965, Tagawa et al. 1076 ( BKF, KYO, L [ L 2842098]).

Preliminary conservation status assessment.

This species is only known from two populations suggesting that this species is endemic to the north-eastern floristic region of Thailand. It is assessed as Data Deficient ( DD) following IUCN (2022). However, S. phengklaii was legally collected from a protected area and it is recorded as common in the locality. Strobilanthes phengklaii has a few records. The changes of the habitat through increasing droughts and fire is likely to lead to the decline of this species. More field work is needed to assess the conservation status of S. phengklaii .

Figures

Figure 6. Strobilanthes phengklaii Kladwong & Chantar. A stem, leaves and inflorescences B adaxial surface of leaf (B 1) and abaxial surface of leaf (B 2) C outer surface of bract (C 1) and inner surface of bract (C 2) D outer surface of bracteole (D 1) and inner surface of bracteole (D 2) E calyx F corolla, stamens and rugula and trichomes retaining the style (arrow) G pistil, style and stigma H ovary I fruit J seed. A – H drawn from Phengklai et al. 12261 (BKF: holotype), I – J drawn from Tagawa et al. 1076 (BKF). Drawn by K. Tuanku.

Figure 7. Scanning electron microscope micrographs of pollen of S. phengklaii Kladwong & Chantar., equatorial view A shape B exine sculpturing, from Phengklai et al. 12261 (BKF).

Figure 11. Distribution maps of Strobilanthes with capitate inflorescence in Thailand A S. graminea J. B. Imlay, S. hypomalla Benoist and S. kerrii Craib B S. paniculiformis J. R. I. Wood, S. paniculata (Nees) Miq. and S. phengklaii Kladwong & Chantar. C S. phyllocephala J. R. I. Wood & Scotland, S. phyllostachya Kurz and S. serpens (Nees) J. R. I. Wood & Scotland D S. speciosa Blume and S. squalens S. Moore.