Asystasia venui Anant Kumar, G. Krishna & Av. Bhattacharjee, 2023

Kumar, Anant, Krishna, Gopal & Bhattacharjee, Avishek, 2023, Asystasia venui (Justicieae: Acanthaceae): A new species from West Bengal, India, Phytotaxa 600 (4), pp. 239-247 : 241-244

Asystasia venui Anant Kumar, G. Krishna & Av. Bhattacharjee sp. nov. FIGURES 2 & 3

Type:— INDIA. West Bengal, Howrah, Acharya Jagdish Chandra Bose Indian Botanic Garden , along bank of Janardanam Lake , 11.3 m, 22.55856° E & 88.29227° N, 20.11.2019, Anant Kumar, Gopal Krishna & Avishek Bhattacharjee 86184 (Holotype CAL, CAL0000033886 ; isotype CAL, CAL0000033887 !) .

Diagnosis:— Asystasia venui is morphologically allied to A. atroviridis Anderson (1867: 526) , but differs in having smaller calyx lobes (vs. longer calyx lobes); papillose ovary (vs. glandular hairy ovary); glabrous style throughout (vs. style pubescent basally); densely glandular pubescent capsules (vs. glabrous capsules).

Description:—Erect or decumbent herbs, 30−60 cm high; stem purplish red, branched, quadrangular, sulcate, ribbed after drying, rooting at nodes on lower portion, pubescent when young, then glabrescent when old except for nodes. Leaves opposite, decussate, petiolate or uppermost pair sessile; petioles (0−) 0.5−8 cm long, sulcate, pubescent; lamina elliptic-ovate to elliptic-lanceolate, uppermost pair ovate to broadly ovate, smaller in size, 1.4−10 × 0.9−4.4 cm, chartaceous, base unequal, rounded, subcordate, attenuate, or decurrent onto petiole when young, margin entire, apex shortly acuminate, pubescent and green above, tuberculate, glabrous and whitish beneath, veins camptodromous, midvein prominent, impressed above, prominent below, pubescent, lateral veins 5−7 pairs, otherwise same as mid vein. Inflorescences terminal, condensed racemes, 1–4 cm long, 4−12-flowered, pubescent. Flowers ca. 2 cm across; pedicels slender, 1−1.2 cm long, pubescent. Bracts triangular, 1.2–1.5 mm long, apex acuminate, margin ciliate persistent; bracteoles ovate-lanceolate, 0.5–0.7 mm long, apex acute, margin ciliate, persistent. Calyx 5-lobed, pubescent and glandular-hairy outside, glabrous inside; tube 1–1.5 mm long; lobes linear-lanceolate, 3−3.5 mm long, apex acute. Corolla infundibuliform, ventricose, white, with a light violet-purple blotch on the middle lobe of lower lip, glandular-hairy outside, glabrous inside; tube 2–2.3 cm long, base cylindrical for 1.5–1.7 cm long, throat 5–6 mm long; lobes 5, elliptic-ovate, 5−7 × 4–4.5 mm, apex obtuse. Stamens 4, didynamous, inserted at base of throat, slightly exserted; filaments white, slender, shorter pair 5−5.5 mm long, longer pair 8−8.5 mm long, connate at the base in pairs, glabrous; anthers white with a vertical violet-black band on the sides, oblong, 1.2–1.5 cm long, spurred at base, connective beyond the anther cells, glabrous. Ovary green, oblong or columnar, compressed, 1.2−1.5 mm long, papillose, basally surrounded by fleshy, dull white, nectariferous disc, 2-celled; ovules 2 in each cell; style white, filiform, 2.4–2.6 cm long, glabrous; stigma shortly 2-lobed, smooth. Capsules green, clavate, compressed, 1.4–2.2 cm long, dehiscent, densely glandular hairy. Seeds 4, suborbicular, flattened, ca. 3 mm across, tuberculate, rugose, dentate along margins, borne on ca. 2 mm long, hook-like retinacula.

Phenology:—Flowering and fruiting from September to December.

Habitat: — The new species grows along lakes in shady area at an elevation of about 10 m. The association includes Rivina humilis L., Ruellia tuberosa L., Cardiospermum halicacabum L., Mikania micrantha Kunth and Plumbago zeylanica L. and grasses etc.

Distribution:—The species is distributed in Howrah, West Bengal, India so far.

Etymology:—The new species is named after Dr Potharaju Venu, Former Senior Scientist of Botanical Survey of India, for his significant contribution to the taxonomy of Indian Acanthaceae .

Notes:— The Indian species of the genus can be categorized in two groups on the basis of shape of corolla tube, i.e. Group 1 comprises three species Asystasia atroviridis Anderson (1867: 526) , A. neesiana ( Wallich 1830: 73) Nees (1832: 89) , A. venui Anant Kumar, G. Krishna & Av. Bhattacharjee sp. nov. having cylindrical, shortly funnelshaped corolla tube upwards, and Group 2 having 10 species A. chelonoides Nees (1832: 89) , A. crispata Bentham (1852: 647) , A. dalzelliana Santapau (1948: 276) , A. gangetica ( Linnaeus 1756: 3) Anderson (1860: 235) , A. indica H.J. Chowdhery & Av. Bhattacharjee (2006: 211) , A. macrocarpa Nees (1832: 89) , A. mysorensis ( Roth 1821: 303) Anderson (1867: 524) , A. pusilla C.B. Clarke (1889: 55) , A. travancorica Beddome (1872: 39) , and A. variabilis (Nees 1847: 165) Trimen (1895: 324) with tubular-ventricose corolla tube ( FIGURE 1 ). Out of these, five species are endemic to India, e.g., A. crispata , A. dalzelliana , A. indica , A. pusilla , and A. travancorica . Lindau (1895) erected a new genus Asystasiella Lindau (1895: 326) to accommodate the species of Group one with two species, viz. A. neesiana and A. atroviridis , and it was considered to be different from Asystasia by having a narrow cylindric corolla tube and stachel pollen (spheroidal with spines). Ensermu et al. (1992) discussed the delimitation of the genus based on pollen morphology. Since, the genus Asystasia encompasses considerable variation in inflorescence form, corolla morphology, and pollen type, therefore, the genus Asystasiella was included within Asystasia ( Manzitto-Tripp et al. 2022) . The generic circumscription of Asystasia , Asystasiella , Mackaya and other related genera should be delimitated by molecular phylogenetic study along with pollen morphology.

Das (1939: 408) incorrectly transferred these three species from Asystasia to Mackaya as M. atroviridis ( Anderson 1867: 526) Das (1939: 448) , M. macrocarpa (Nees 1832: 89) Das (1939: 447) , and M. neesiana ( Wallich 1830: 73) Das (1939: 447) , respectively. However, the genus Mackaya is characterized by two fertile stamens without spurs and with two staminodes, while Asystasia has all four fertile stamens with spur at the base of anthers. Deng and Wu (2009: 308) stated that these three species were quite different from Mackaya in having four stamens and they preferred to place them in Asystasia rather than in Mackaya . Based on the above mentioned reasons the new species fits with Asystasia instead of Mackaya and hence, we are describing it here under Asystasia .

The new species was wrongly identified as Asystasia chelonoides Nees by Chowdhery and Pandey (2007). However, it can be easily distinguished from Asystasia chelonoides by its long tubular-cylindrical corolla and densely flowered racemes.

Comparison of diagnostic characters of the new species with its most allied species is provided in detail in Table 1.

Additional specimens examined (Paratypes):— INDIA. West Bangal: Acharya Jagdish Chandra Bose Indian Botanic Garden, along bank of Janardanam Lake , 10 m, 22.55847° E & 88.29214° N, 23.11.2020, Anant Kumar, Gopal Krishna & Avishek Bhattacharjee 86185 ( CAL) ; Acharya Jagdish Chandra Bose Indian Botanic Garden, along bank of Janardanam Lake , 11 m, 22.55862° E & 88.29233° N, 20.11.2018, Anant Kumar, Gopal Krishna & Avishek Bhattacharjee 81601 ( CAL) ; Acharya Jagdish Chandra Bose Indian Botanic Garden, Division 9, 12 m, 22.55746° E & 88.29357° N, 23.09.2010, Avishek Bhattacharjee 72736 ( CAL) .

Figures

FIGURE 1. Corolla (without indumentum) of Indian species of Asystasia: Group-I: A1, A2. A. atroviridis; B1, B2. A. neesiana; C1, C2. A. venui Group-II: D1, D2. A. chelonoides; E1, E2. A. crispata; F1, F2. A. dalzelliana; G1, G2. A. gangetica; H1, H2. A. indica; I1, I2. A. macrocarpa; J1, J2. A. mysorensis; K1, K2. A. pusilla; L1, L2. A. travancorica; M1, M2. A. variabilis (illustrated by Anant Kumar)

FIGURE 2. Asystasia venui: A. Habit; B. Leaves; C. Front view of flower; D. Bract; E. Bracteoles; F. Dorsal view of calyx splits open; G. Ventral view of calyx splits open; H. Lateral view of corolla with calyx; I. Dorsal view of corolla splits open; J. Ventral view of corolla splits open; K. One pair of stamens; L. Style with calyx; M. Ovary; N. Disc; O. Fruits; P. Seeds. (Photographed by Anant Kumar)

FIGURE 3. Asystasia venui: A. Habit; B. Bract; C. Dorsal view of calyx splits open D. Lateral view of corolla with calyx; E. Stamens; F. Style with calyx; G. Ovary; H. Fruits. (illustrated by D.K. Sah based on Kumar et al. 86184)