Fagopyrum homotropicum Ohnishi (1998: 20)

Ding, Mengqi, Zhang, Kaixuan, Tang, Yu, Wang, Junzhen, Li, Faliang, Yang, Keli, Wen, Wen & Zhou, Meiliang, 2021, Newly discovered tetraploid Fagopyrum homotropicum in Tibet, China, Phytotaxa 528 (3), pp. 202-208 : 203-206

Fagopyrum homotropicum Ohnishi (1998: 20) .

Type: — CHINA. Tibet Autonomous region: Mangkang County, 2200–2500 m a.s.l., 20 September 2017, Zhou 201709 (holotype CAAS2204 !) .

Diagnosis: — Tetraploid form of Fagopyrum homotropicum is similar to diploid form but it is differs by their shape and size of grains, which are bigger and slender than that of diploid form (see Table 1 , Figs. 1–3 ).

Description:—Plants annual, herbaceous, 70–124 cm tall. Stems erect or semi-erect (= stem is erect for the distal half of its length), branching from basal or lower-middle nodes. Stems terete, glabrous, fuchsia coloured, with surface smoothly and longitudinal ribs. Leaves alternate, narrowly ovoid, triangular-ovate or ovate-triangular (2.0–6.2 × 1.5–5.3 cm), adaxially green or reddish-green, abaxially dark-green, sparsely pubescent on both surfaces; petioles 4.3–5.0 cm long, and the middle and upper petioles gradually become shorter to none; stipules thick membranous, obliquely tubular, sparsely white pubescent. Inflorescences racemose, axillary or terminal, 0.7-4.0 cm long, with dense cyme clusters inserted in the upper or middle-upper part of the inflorescence axis; bracts funnel-shaped, oblique with an acuminate apex, green, flowers 2–3 for each bract; pedicel linear, green or red-green, glabrous, with articulate; tepals 5 (2 smaller on the outside and 3 bigger on the inside), oval or ovate, 2.3–2.5 mm × 1.3–1.6 mm, white and light-green basally; stamens 8, arranged in 2 whorls (5 in outer and 3 in inner), anther elliptic, red or fuchsia, 0.2–0.3 mm, ovary ovoid triangular pyramidal, 0.7–0.8 mm long, yellow-green, styles 3, white, glabrous, stigma capitate, pistil and stamens has the same length (homostyled). Achenes broadly oval triangular pyramidal or triangular pyramidal, 4.4–5.5 mm long and 3.8–4.6 mm in diameter, with sharp or slightly blunt apex and sharp fruit edges; the skin of fruits is black-brown or brown when ripe, surface rough and lackluster, the tepals are persistent, and the achene is 2–3 times exposed to the tepals; styles persistent. ( Figs. 1–2 ).

Etymology:—The specific epithet refers to the homostyled character.

Distribution and habitat:—Tetraploid form of Fagopyrum homotropicum is known from the barren hillside and rock piles in southwest China, especially the junction area of Tibet and Yunan. It grows at elevation 2200–2500 m a.s.l.

Phenology:—Flowering time July–September; fruiting time August–October.

Pollination:—Two years of field cultivated experiments stated that the inheritance of tetraploid form of Fagopyrum homotropicum was stable, it is self-pollination and could fruits normally without manual intervention.

Morphological remarks:—Based on the observation under the wild and field environment, tetraploid and diploid forms of Fagopyrum homotropicum are quite similar in morphological characters, both of them being homostyled, the characters of flower organs are undifferentiated while the shape and size of grains have a small difference.

Chromosome numbers:—Tetraploids with 2n=4x=32, diploids 2n=2x=16 ( Fig. 4 ).

Figures

FIGURE 1. Tetraploid form of Fagopyrum homotropicum in different stages.A) Seedling stage, B) Flowering stage, C) Fruit setting stage, D) Plants in the wild environment.

FIGURE 2. Morphology of flower and fruits of Tetraploid form of Fagopyrum homotropicum: A) Flower when overlooking, B) Flower when side-looking, C) Immature seed, D) Mature seed.

FIGURE 3. Morphology of flower and fruits of diploid form of Fagopyrum homotropicum: A) Flower when overlooking, B) Flower when side-looking, C) Immature seed, D) Mature seed.

FIGURE 4. Chromosome analysis of Tetraploid form of Fagopyrum homotropicum.