Amaranthus cruentus L.

Hassan, Walaa A., Al-Shaye, Najla A., Alghamdi, Salma, Korany, Shereen M. & Iamonico, Duilio, 2022, Taxonomic revision of the genus Amaranthus (Amaranthaceae) in Saudi Arabia, Phytotaxa 576 (2), pp. 135-157 : 152-153

12. Amaranthus cruentus L. , Syst. Nat., ed. 10. 2: 1269. 1759

Type (lectotype designated by Townsend 1974: 12):— CHINA. Habitat in China , Herb. Linn. No. 1117.25 (LINN!, image of the lectotype available at http://linnean-online.org/11651/) .

= Amaranthus flavus L., Syst. Nat., ed. 10. 2: 1269. 1759.

Type (lectotype designated by Iamonico 2014a: 147):—UNKNOWN ORIGIN. Herb. Linn. No. 1117.23 (LINN!, image of the lectotype available at http://linnean-online.org/11649/).

= Amaranthus paniculatus L., Sp. Pl., ed. 2. 2: 1406. 1763.

Type (lectotype designated by El Hadidi & El Hadidy 1981: 37):—AMERICA. Habitat in America , Herb. Linn. No. 1117.20 (LINN!, image of the lectotype available at http://linnean-online.org/11646/) .

= Amaranthus sanguineus L., Sp. Pl., ed. 2. 2: 1407. 1763.

Type (lectotype designated by Iamonico 2014a: 148):—UNKNOWN ORIGIN. Herb. Linn. No. 1117.21 (LINN!, image of the lectotype available at http://linnean-online.org/11647/).

Description:— Herbs 5–14 dm tall, monoecious, annual (therophyte). Stems erect, ± glabrous (slightly pubescent in the upper part), red or green, often distally branched. Leaves usually green, ovate to ovate-lanceolate, rhomboidal [(3.0–)5.0–12.0(–14.0) × (1.5–)3.0–6.0(–7.0) cm], with entire margins, apex acute or obtuse (sometimes slightly emarginate), mucronate, base cuneate, glabrous or slightly pubescent, petioled (petiole 1.5–10.0 cm long). Synflorescences terminal, panicle-like, the main florescence up to 15 cm long (longer than the paraclades), red or green. Floral bracts green or greenish, lanceolate (2.0–3.5 × 0.8–1.3 mm), 1.0–1.5 longer than the perianth, acute, awned, with membranous border abruptly interrupted at the half, margin entire, glabrous. Staminate flowers with 5 tepals, ovate-lanceolate; stamens (4–)5. Pistillate flowers with 5 tepals, ovate-lanceolate [(1.5–)2.0–2.5(–3.0) × 0.6–1.5 mm], with acute and sometimes mucronate apex, median vein usually yellow-brown; stigmas 3. Fruit brown, ellipsoidal (2.0–2.5 × 1.4–1.6 mm), longer than the perianth, smooth to slightly rugose, dehiscent. Seed lenticular (1.2–1.6 mm in diameter), dark-brown to reddish-brown.

Iconography:— Willdenow (1790: Tab. II fig. 4, sub A. paniculatus ), Beck (1909: Tab. 296, figures 3–4, sub Euxolus patulus ), Bayón (2015: 280, Figura 7).

Chromosome number:— 2n = 32, 34.

Alien status:— Neophyte species native to Central America, it can be considered as naturalized in Saudi Arabia ( Chaudhary 1998).

Occurrence in Saudi Arabia:— Chaudhary (1998) indicated this species [sub Amaranthus hybridus subsp. cruenthus (L.) Thell.] in “the southwest of Saudi Arabia”, without further data about the localities in which it occurs. No finding was done during the filed surveys. Further researches are necessary to verify the distribution of A. cruentus in the country.

Taxonomic annotations:— Amaranthus cruentus is quite variable from the morphological point of view, especially concerning the surface of the leaf blade (simple green, green with a white band arch-shaped, or green with a central red spot), the structure of the synflorescences (the paraclades can be erect to patent), and the colour of the stem and synflorescence (from green to red or dark-red). Some cultivars ( A. cruentus is also used as ornamental plant), especially those with dark-red synflorescences, can be confused with some forms of A. hypochondriacus , but the two species differ each other by the characters of the bracts (see Iamonico 2015).