Amomum pratisthana J.Sarma, S.Dey, C.K.Salunkhe & Barbhuiya, 2019

Sarma, Jatindra, Dey, Santanu, Salunkhe, Chandrakant Krishnaji & Barbhuiya, Hussain Ahmed, 2019, A new species of Amomum (Zingiberaceae) from Assam, North East India, Phytotaxa 391 (2), pp. 163-166 : 163-165

Amomum pratisthana J.Sarma, S.Dey, C.K.Salunkhe & Barbhuiya , sp. nov. ( Fig.1 )

The new species differs from Amomum trilobum Gagnepain (1904: 453) in having loosely clasping leaf-sheaths to its pseudostem, unlobed labellum, cuspidate apex of dorsal corolla lobe and by the absence of tooth-like lobe at the base of anther crest.

Type:— INDIA. Assam: Tinsukia District, Digboi Forest Division, Upper Dihing Reserve Forest, West Block, Soraipung, 27°20 ʹ 47.2 ʹʹ N & 95°30 ʹ 4.5 ʹʹ E, alt. ca. 96 m, 18 April 2013 (flowered in cultivation on 17 May 2017), J. Sarma 300 (holotype: HBARC-00006380!, isotype: CAL!).

Rhizome creeping, internodes 0.5–3.0 cm long, 0.3–0.5 cm in diameter, nodes covered with amplexicaul sheaths; sheaths ovate to oblong-ovate, 0.8–2.0 × 1.0– 1.5 cm, pinkish to reddish in colour; rhizomes producing leafy shoots at an interval of 6–8 cm. Roots coming out from the nodes of rhizomes and from the base of leafy shoots, slender, sometimes branching. Young shoots starts with a single leaf with two amplexicaul sheaths at base; sheaths oblong-lanceolate, 4.0–9.0 × 1.0– 1.5 cm, canaliculate. Pseudostem not well developed, up to 22 cm high, with loosely clasping leaf-sheaths at base. Leaves usually 5–6 per mature shoot; sheaths canaliculate, 10–20 cm long, glabrous; ligule unlobed, 3–8 mm long, glabrous; petiole channeled, 3.5–19 cm long, 3–4 mm wide; lamina oblong-lanceolate, 15–30 × 5.5–9.0 cm, both surfaces glabrous, green with prominent veins, young leaves reddish beneath, leaf apex acuminate, shortly caudate, base attenuate or sub-cuneate while young. Inflorescence arising from the base of leafy shoots; scape covered with bracts, 1.5–2.5 cm long, bearing a cluster of 5–flower at apex. Bracts 5–8, deltoid, ovate to cymbiform, 0.5–5.0 × 0.5–1.3 cm, ruby-pink, apex acute. Bracteole oblong-lanceolate, 3.4–3.6 × 0.5–0.8 cm, membranaceous with pink veins. Flower 8.0– 8.5 cm long, creamy with pinkish tinge on calyx and corolla, lip with a central yellow crest. Calyx tubular, 3.6–4.0 × 0.3–0.5 cm, glabrous, one side is split down up to 1.7 cm from the top, the other side is with 2 small teeth of ca. 2 mm height. Corolla tube 3.5–4.0 cm long, 2.5–3.0 mm in diameter; lobes membranaceous; dorsal lobe cymbiform, 2.7–4.0 × 1.0– 1.2 cm, apex cuspidate, cusp ca. 5 mm long, slightly curved with a broad base; lateral lobes oblong, ca. 2.5 × 0.5 cm, reflexed at the middle, apex obtuse, slightly hooded. Labellum obovate, unlobed, 3.5–4.0 × 2.2–2.5 cm, reflexed, heavily veined, margins slightly crenate-undulate, white to cream coloured with median thick yellow portion. Lateral staminodes absent. Stamen 1.8–2.0 × 0.5–0.6 cm; anther-thecae 7–8 mm long; crest obtusely triangular, ca. 4 × 3 mm, slightly reflexed. Stigma obconic, 1.0– 1.5 mm long, held near the apex of anther-thecae; style filamentous ca. 4.5 cm long; ovary ca. 6 × 3 mm, trilocular. Fruit not seen.

Distribution:—Endemic to Tinsukia district of Assam, India. Currently known from three localities viz. Soraipung and Lakhipothar of Upper Dihing R.F. and from West Block of Digboi R.F.

Ecology & Habitat:—Growing along forest margins, often in ditches where no water logging was observed. The soil of the habitat is sandy loam and there is no direct sunlight. The associated species are mainly herbs, for example Colocasia lihengiae, Lasia spinosa, Tacca chantrieri, Psychotria sp. etc.

Eponymy:—The specific epithet is for the daughter of first author, Miss Pratistha Sarma, who currently pursuing a medical degree. She inspired and continually appreciated her father for performing botanical explorations. The meaning of Pratistha is establish or foundation.

Phenology:—Flowers in the month of May.

Conservation Status:—The species occurs sporadically in three localities. The area of occupancy (AOO) is estimated as 8 sq. km and the extent of occurrence (EOO) is estimated to be 1279 sq. km. But, there is no continuous decline in AOO, EOO, quality of habitat or number of location and subpopulations. Hence, the species is categorized under Least Concern (LC).

Note:— Amomum pratisthana shows superficial similarity with A. trilobum in having one to multiple leaves per shoot, a prominent leaf ligule, by bearing inflorescence in the form of a compact head, but differs in several respect, e.g. by having a weakly developed pseudostem, an unlobed labellum, a cuspidate apex to the dorsal corolla lobe, and by the absence of tooth-like lobe at the base anther crest, etc. A detailed morphological comparison between the two species is provided in Table 1.

Figures

FIGURE 1. Amomum pratisthana A. Lower portion of the plant showing rhizome, roots, pseudostem and inflorescence. B. Upper portion of plant showing leaves and petioles. C. Pseudo stem base showing loosely attached leaf sheaths and inflorescence. D–E. Ligules. F. Inflorescence with bracts. G. Inflorescence without bract. H. Bract. I. Bracteole. J. Flower with bracteole. K–L. Flower without calyx-top view. M. Flower-side view. N. Magnified view of flower showing corolla lobes and labellum. O. Flower bud showing calyx. P. Flower base showing calyx. Q. Labellum with dorsal corolla lobe. R. Corolla with stamen and carpel. S. Corolla tube with stamen and carpel. T. Stamen. U. Stigma with upper portion of styles. V. Ovary. All based on J. Sarma 300 (HBARC!).