Alternanthera ebracteolata S. Arya & V.S.A Kumar, 2021

Arya, Sindhu & Kumar, Venugopalan Nair Saradamma Anil, 2021, Alternanthera ebracteolata (Amaranthaceae), a new species from Kerala (SW- India), Phytotaxa 480 (3), pp. 277-283 : 278-282

Alternanthera ebracteolata S. Arya & V.S.A Kumar , sp. nov.

Type: — INDIA. Kerala: Kasaragod district, Udayagiri , 28 m, 12°49 ’ N, 75°48 ’ E, 20 th October 2019, Anil Kumar & Arya (holotype TBGT! , isotypes CMPR!, HFLA!) .

Diagnosis: — Alternanthera ebracteolata is morphologically similar to A. tenella Colla (1829: 131) but differs mainly in having peduncled inflorescence, 4–5 flowers per glomerule, linear to lanceolate shaped whitish bracts, absence of bracteoles, markedly pubescent sepal, appendages on androecial tube equaling the length of stamens and globose seeds.

Description (macromorphology, Figs. 1–2 ): —Monoecious, annual therophytes, ascending, prostrate or trailing, 100–120 cm tall. Stem ascending or erect, angular, solid, green, purple at nodes, glabrous or sparsely pubescent, branched with prominent nodes. Leaf simple, opposite, not fleshy, petiole 2–2.5 × 1.5–2.2 cm glabrous, blade ovate 4.5–5.5 × 2.5–3 cm, dark green, margin entire or wavy, pubescent, apex acute to slightly ovate. Trichomes simple, multicellular, eglandular, present along the margin and adaxial surface. Synflorescence arranged in axillary peduncled glomerules, one from each node; peduncle green, terete, sparsely pubescent 1.5–2.5 × 0.4 – 0.5 cm. Flowers bisexual, 10–14 in each glomerule. Sepals arranged in 2 whorls; Outer sepals ovate, 1.5–2.2 × 0.5–1.0 mm, acute, apex pointed and often recurved, highly pubescent; trichomes simple, densely arranged at the base of the sepal, scattered in the middle and absent at the tip, white, slender with round apex. Inner sepals 4–5, lanceolate-ovate, 0.8–1.0 × 0.3–0.4 mm, white to transparent, apex acute and recurved, glabrous. Bract white, linear to lanceolate, small 0.8–1.0 mm, shorter than tepal, margin entire, apex acute, glabrous. Bracteoles absent. Stamens short, 5 in number, unite one another at the base of the ovary, forming a rim like structure, not fused with the ovary. Appendages on the androecial tube equal the length of stamens (0.3–0.4 mm), white, transparent, apex slightly dentate, margin entire. Gynoecium 0.2–0.3 mm long, style short, glabrous, stigma glandular. Fruit 0.5 mm long, wrinkled surface texture throughout, white. Seeds whitish green, 0.6–0.9 mm, globular.

Description (micromorphology, Fig. 3 ): —Pollen grains dodecahedric, with 5–6 pores. The size of the pollen is 15.54 µm across. Distance between 2 pores is 3.12 µm Pore membrane 3.45 µm; ektexinuous bodies 50–60, nanospine 80–120. Metarecticulum roughly circular in outline 4.62–6.25 µm wide; structural elements and conjunction points 5. Mesoporium 1.25–1.45 µm wide, sculpture punctate, nano-microspinulate 5-6 nanospore per structural element. Tectum on structural element 0.25 µm long, tectum on conjunction point 0.38 µm high. Collumellae on conjunction point 0.5 µm; nexine of conjunction point 0.21 µm thick, nexine of structural element 0.32 µm; sexine of conjunction point 0.7 µm thick, sexine of structural element 0.9 µm thick.

Seeds are globose, 0.6–0.7 × 0.7–0.8 mm in sizes, surface with rectangular to hexagonal shaped cells towards the margin and centre smooth. Each cell measures 10–12 × 4–6 µm.

Etymology:—The specific epithet corresponds to the unique trait of the specimen – absence of bracteoles.

Phenology:—Flowering and fruiting times June–January.

Distribution and ecology:— Alternanthera ebracteolata grows in the barren dry lands and roadsides in several locations of Kasaragod district of Kerala. The species grows as small populations, each comprising 4–6 scattered plants.

Conservation status:— Alternanthera ebracteolata is known from 4 locations only (for a total of 50 individuals), and the AOO (Area Of Occupancy) is 5 km 2. The habitat has been greatly reduced due to intense anthropogenic pressure for urbanisation. On the basis of the IUCN Red List criteria ( IUCN 2019) and the available data, we can apply the criteria B2 and C2ai and assess Alternanthera ebracteolata as Critically Endangered (CR) species.

Alternanthera ebracteolata is morphologically similar to A. tenella in having alternate appendages on androecial tube and stamens forming a rim at the base of ovary but differ from it in many key characters. In A.ebracteolata , the appendages on androecial tube equal the length of stamens (0.3–0.4mm), white, transparent, slightly dentate at the apex with entire margin while in A. tenella , it is oblong, equaling or slightly longer than stamens (1.7 mm long), laciniate, deeply dentate and yellowish at apex. It is also distinct in having a peduncled inflorescence while it is sessile in A. tenella . In A. ebracteolata , glomerules (1–1.2 × 0.5–0.6 cm) are at the nodes, prominently peduncled 1.0– 1.5 cm with 10–14 flowers in each, while in A. tenella , glomerules (0.5 –0.7 × 0.4–0.8 cm) are not peduncled and each has 2–3 (rarely 4) flowers. The bracts narrow, linear to often lanceolate, white and small, shorter than tepals with total absence of bracteole in A. ebracteolata , while in A. tenella the shape of the bract and bracteole is lanceolate to ovate (2.0–3.4 × 0.9–1.0 mm), yellowish or whitish, shorter than the sepal, carinate or not, apex acuminate or aristate, margin entire, glabrous or pubescent. The shape of the sepal is ovate, apex aristate often reflexed and highly pubescent in A. ebracteolata , whereas in A. tenella , the sepals are ovate to lanceolate (3.0–4.5 × 0.5–1.4 mm) with apex mucronate to aristate, margin entire, pubescent. The shape of the seed is globular in A. ebracteolata where as in A. tenella , the seed is lenticular in shape.

The new species is also similar to Alternanthera philoxeroides ( Martius 1825: 107) Grisebach (1879: 36) in having a peduncled inflorescence. However, A. philoxeroides grows as radicant hydrophyte, diffuse hemicryptophyte or chamephyte, which differs from the new species in having tepals lanceolate to oblong and glabrous while it is ovate and highly pubescent in A. ebracteolata . Leaves of A. philoxeroides are lanceolate or elliptic (2.5–10.0 × 0.3–2.0 cm) with apex acute to obtuse and mucronate while in A. ebracteolata , the shape of leaf blade is ovate with acute or ovate apex. The stem of A. philoxeroides is prostrate mat forming stoloniferous, hollow with rooting at nodes while in A. ebracteolata the stem is erect or prostrate and angular. The bracts and bracteoles in A. philoxeroides is yellowish or greenish, shorter than tepals, ovate to lanceolate (2.0–2.5 × 1.0– 1.2 mm) with apex acute or mucronate, while in A. ebracteolata , bracteoles are absent and bracts are white, linear to lanceolate. The shape of sepal is lanceolate (5.5–6.0 × 1.5–2.5 mm), in A. philoxeroides with apex often acute or rounded and glabrous while in A. ebracteolata , the shape of sepal is ovate, pubescent with acute apex. The appendages on androecial tube are oblong (1.5–1.8 mm long) and shorter than stamens in A. philoxeroides while in A. ebracteolata , appendages on androecial tube equal the length of stamens and the apex is dentate. The shape of seeds is lenticular in A. philoxeroides while it is globose in A. ebracteolata .

Additional specimens examined (paratypes):— INDIA: Kerala: Kasaragod District, Periya 16 m, 26 January 2019, Anil Kumar & Arya 16523 ( TBGT!) , Kollam District, Punalur, 8 m, 29 August 2019, Anil Kumar & Arya 83425 ( CMPR!) , Thiruvananthapuram district, along coastal side, 8 m, 25 January 2020, Anil Kumar 83568 ( TBGT!) .

Figures

FIGURE 1. Alternanthera ebracteolata. a. habit; b. synflorescence; c. flowering twig; d. inflorescence; e. flower; f–g. appendages on androecium and stamen; h. Outer sepal; i. inner sepal; j. gynoecium; k. seed.

FIGURE 2. Alternanthera ebracteolata. a. habit; b. synflorescence; c. flower; d. cross section of flower; e. appendages on androecium; f. outer sepal; g. inner sepal; h. gynoecium; i. seed.

FIGURE 3. SEM images of Alternanthera ebracteolata a. pollen; b. close up of pollen showing pores; c. seed surface (middle region); d. seed surface (margin).