AMORPHOPHALLUS SAKONNAKHONENSIS

PROTOLOGUE: Amorphophallus sakonnakhonensis Chatan & Promprom, published in PhytoKeys 229: 131-138 (2023).

Amorphophallus sakonnakhonensis Chatan & Promprom, sp. nov. Type. Thailand. Sakon Nakhon Province: Khok Sri Suphan District, northeastern Thailand, 300-320 m elev., 16°59'45.5"N, 104°15'46.9"E, 24 April 2021, W. Chatan 2897 (holotype: BKF!; isotype: BK!); Khok Sri Suphan District, W. Chatan 3073 (paratype: BKF!), 29 June 2022.

DISTRIBUTION: Thailand: Thailand.

DISTRIBUTION NOTE: Thailand: Khok Sri Suphan District in Sakon Nakhon Province, the only locality known.².

SPECIES DESCRIPTION:

A perennial herb, small in stature and reaching only about 12 cm high whether in leaf or in flower. Tuber narrowly elongate, not branching, 5-10 cm long and 0.4-1.0 cm across, the skin light yellowish to yellowish brown, with few to many fibrous lateral roots. Leaf solitary; petiole 2.5-2.8 by 0.2-0.3 cm, smooth, white near the base and greenish-purple or dark dull red to rust-coloured above; blade up to 10 cm across, the rachis narrowly winged throughout; leaflets elliptic or obovate, about 0.5-3.0 by 0.3-0.5 cm, green above and pale green beneath, the apex acuminate.²

INFLORESCENCE:

Inflorescence solitary and produced before the leaf; peduncle 3.0-5.5 cm long and 2.0-2.5 mm across, white near the base and greenish to greenish-purple above. Spathe broadly ovate, 2.0-2.2 by 1.5-1.8 cm, dull greenish yellow or creamy white on both sides except for a deep purple-red or bluish purple base within, erect, embracing the spadix and standing close to it with the upper part moving slightly away at anthesis, smooth on both surfaces except for the warted lower part within. Spadix about equalling or longer than the spathe, 2-3 cm long, the female and male zones touching though the flowers stand slightly apart where they meet. Female zone cylindrical, about 1.0 by 0.5 cm, the axis green, most flowers slightly apart; ovary depressed, shallowly two-lobed, about 1 by 1 mm, light green; style short and thick, about 1 mm long; stigma about 0.2 by 0.1 mm, creamy or yellowish, disc-like with a slightly smooth surface and a concave centre. Male zone slightly cylindrical, 1.5-2.0 by 0.6-0.8 cm, narrower in its upper part; male flowers fused into a synandrium of 3-5 stamens, creamy or yellowish, the filaments united into a short column about 1.0 by 0.8-1.2 mm. Appendix slightly cylindrical to elongate-fusiform, 1-3 by 0.8-1.0 cm, erect or nearly so, creamy white, the apex obtuse to slightly acute, the surface smooth. Berry green both young and ripe, conical to broadly pear-shaped, shallowly two-lobed, about 0.5 by 0.5 cm, drawn out in its upper part, odourless, the surface warted. Seed ellipsoid or ovoid, 2.5-3.5 by 1.0-1.3 mm, the apex conical.²

ECOLOGY:

Recorded at 300-320 m. It flowers in May and June and fruits from June to August.²

DISTRIBUTION MAPS:

ETYMOLOGY:

From Sakon Nakhon, the province in north-eastern Thailand where the type was gathered. It is known locally as Buk Noi.²

NOTES:

1. The species is closest to Amorphophallus harmandii and Amorphophallus linearis, sharing with both a narrowly elongate tuber, a spadix longer than the spathe, and male and female zones that touch.²

2. From Amorphophallus harmandii it differs in a shorter style, about 1 mm against 2-3 mm; a disc-like stigma about 0.2 by 0.1 mm rather than a depressed, shallowly two-lobed one about 0.6 by 1.5 mm; a male zone that is slightly cylindrical and narrower above rather than fusiform-conical or flask-shaped with a swollen base; and a creamy white appendix that stands erect rather than a very narrow, mouse-tail-like or forward-curving one.²

3. From Amorphophallus linearis it differs in that same small disc-like stigma against a capitate, globose one 1.0-1.3 by 0.9-1.5 mm; in elliptic or obovate rather than linear leaflets; and in an appendix of 1-3 cm against 18-50 cm.²

4. The berries are green rather than brightly coloured, and warted - a character the authors call near-unique and use to place the species in the Amorphophallus harmandii alliance.²

5. It is known from a single population, and the authors assessed it as Data Deficient.²

REFERENCES:

1. Plants of the World Online, Royal Botanic Gardens, Kew — Amorphophallus sakonnakhonensis Chatan & Promprom

2. PhytoKeys 229: 131-138 (2023) — protologue.