Amorphophallus sakonnakhonensis Chatan & Promprom, 2023

Promprom, Wilawan, Chatan, Wannachai, Pasorn, Pattana, Prasertsri, Narueset & Angkahad, Thinnakon, 2023, A new species of Amorphophallus (Araceae) from northeastern Thailand, PhytoKeys 229, pp. 131-138 : 131

Amorphophallus sakonnakhonensis Chatan & Promprom sp. nov.

Figs 1 , 2 , 3 , 4

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 , northeastern Thailand, W. Chatan 3073 (paratype: BKF!), 16°59'45.5"N, 104°15'49"E, 29 June 2022 .

Diagnosis.

Amorphophallus sakonnakhonensis is most similar to A. harmandii Engl. & Gehrm. and A. linearis Gagnep. The essential differences with A. harmandii are shorter style (ca. 1 mm vs. 2-3 mm long); disc-like, slightly smooth surface, concave centre, ca. 0.2 × 0.1 mm stigma vs. depressed, shallowly bilobed, ca 0.6 × 1.5 mm; slightly cylindrical, narrower upper part staminate flower zone vs. fusiform-conical or lageniform with distinctly dilated basal haft; slightly cylindrical to elongate-fusiform, erect or slightly erect, creamy white appendix vs. very narrowly conical, near myosuroid or fusiform conical or slightly sigmoidally curved forward in the lower half, white or greenish yellow.

The essential differences with A. linearis are disc-like, slightly smooth surface, concave centre, ca. 0.2 × 0.1 mm stigma vs. capitate, globose, 1.0-1.3 × 0.9-1.5 mm; elliptic or obovate leaflet vs. linear less often lanceolate; 1-3 cm long, creamy white appendix vs. 18-50 cm long, creamy white or green.

Description.

Perennial herb, narrowly elongated, not branching, 5-10 cm long and 0.4-1.0 cm diam., skin light yellowish to yellowish brown with few or many fibrous lateral roots. Both flowering and leafing plants of small stature, up to 12 cm high. Leaves solitary. Petiole 2.5-2.8 × 0.2-0.3 cm, smooth, white near base and greenish-purple or dark dull red to dark red or rust-coloured at upper part; leaf blade up to 10 cm diam., rachis narrowly winged throughout; leaflet elliptic or obovate, ca. 0.5-3.0 × 0.3-0.5 cm, adaxial side green, abaxial side pale green, apex acuminate. Inflorescence solitary, developed before leaf; peduncle 3.0-5.5 cm long, 2.0-2.5 mm diam., white near base and greenish to greenish-purple at upper part; spathe broadly ovate, both sides dull greenish yellow or creamy white excepting for the deep purple red or bluish purple at base adaxially, 2.0-2.2 × 1.5-1.8- cm, erect, embracing and close to spadix and upper part moving slightly away from spadix during anthesis, smooth on both surfaces, except for lower part verrucate adaxially; spadix subequal or longer than spathe, 2-3 cm long; pistillate and staminate flower zones contiguous, but flowers are slightly distant from each other at connection zone. Pistillate flower zone cylindrical, ca. 1.0 × 0.5 cm, axis green, most flowers slightly distant from each other; ovary depressed, shallow bilobed, ca. 1 × 1 mm, light green; style short, thick, ca. 1 mm long; stigma ca. 0.2 × 0.1 mm, creamy or yellowish, disc-like, surface slightly smooth, centre concave. Staminate flower zone slightly cylindrical, 1.5-2.0 × 0.6-0.8 cm, upper part narrower; staminate flowers fused to a synandrium consisting of 3-5 stamens, creamy or yellowish; filaments united into a short column, ca. 1.0 × 0.8-1.2 mm, whitish or creamy. Appendix slightly cylindrical to elongate-fusiform, 1-3 × 0.8-1.0 cm, erect or slightly erect, creamy white; apex obtuse to slightly acute; surface smooth. Berry green when young and mature, conical to broadly pyriform, shallowly bilobed, ca. 0.5 × 0.5 cm, upper part elongated, odourless, surface verrucate. Seed ellipsoid or ovoid, 2.5-3.5 × 1.0-1.3 mm, apex conical.

Flowering and fruiting.

Flowering in May-June and fruiting in June-August.

Distribution.

The new species is endemic to Thailand and is known from only the type locality, Khok Sri Suphan District, Sakon Nakhon Province, northeastern Thailand (Fig. 4 ).

Ethymology.

Specific epithet of A. sakonnakhonensis refers to the type locality, Sakon Nakhon Province, northeastern Thailand.

Vernacular name.

The Vernacular name of the new species is Buk Noi.

Preliminary conservation status.

According to the fieldwork, one population of Amorphophallus sakonnakhonensis was found at the type locality in Khok Sri Suphan District, Sakon Nakhon Province, northeastern Thailand. However, further explorations are needed for a proper conservation assessment because more information on its distribution and population status is required. Therefore, the species has been preliminarily assigned to Data Deficient (DD) category according to The Guidelines for Using The IUCN Red List Categories and Criteria (IUCN, 2022).

Discussion.

Amorphophallus sakonnakhonensis Chatan & Promprom is similar to A. harmandii Engl. & Gehrm. ( Engler 1911) and A. linearis Gagnep. ( Gagnepain 1941), the plants from Thailand and Indochina ( Hetterscheid 2012). The new species would be placed in subgenus. Amorphophallus Metandrium ( Claudel et al. 2017), based on the hypothesis on the phylogenetic affinity of the species, which clearly lies with the A. harmandii alliance, close to that species, particularly seen by the near-unique fruits (green, warty). Similarities to A. harmandii and A. linearis consist of the narrowly elongated tuber, spadix longer than spathe, and contiguous nature of the staminate and pistillate flower zones. The different morphological characters are described below. The main differences of the new species from A. harmandii are that it has shorter style; disc-like, slightly smooth surface, concave centre stigma; slightly cylindrical staminate flower zone; slightly cylindrical to elongate-fusiform, erect or slightly erect, creamy white appendix. The new species is also different from A. linearis by its disc-like, slightly smooth surface, concave centre stigma; elliptic or obovate leaflet; 1-3 cm long, creamy white appendix. In addition, the size of these organs of the new species are smaller or slightly smaller, including tuber, petiole, leaf blade, peduncle, spathe, spadix, staminate flower zone and appendix. More details of morphological differences amongst A. sakonnakhonensis , A. harmandii Engl. & Gehrm. and A. linearis Gagnep. are presented in Table 1 .

Figures

Figure 1. Amorphophallus sakonnakhonensis Chatan & Promprom. A habitat and habit B habit.

Figure 2. Amorphophallus sakonnakhonensis Chatan & Promprom. A whole plant B, C tuber and inflorescence from the same plant D spadix E infructescence and fruits F seeds.

Figure 3. Amorphophallus sakonnakhonensis Chatan & Promprom. A whole plant B, C tuber and inflorescence from the same plant D seeds E spadix F staminate flowers G pistillate flowers H infructescence and fruits I fruit.

Figure 4. Distribution of Amorphophallus sakonnakhonensis Chatan & Promprom (green circle).