Impatiens dalaiensis Gogoi & Borah, 2015

Gogoi, Rajib & Borah, Souravjyoti, 2015, Impatiens dalaiensis (Balsaminaceae) a new species from Arunachal Pradesh, India, Phytotaxa 207 (3), pp. 286-290 : 286-287

Impatiens dalaiensis Gogoi & Borah sp. nov. ( Figure 1 & 2 A–G )

Differs from I. radiata Hooker by stem bases terete, flower buds with a prominent awn, lower sepal mouth with a distinct awn or appendage, distal lobes of lateral united petals long ribbon shaped, twisted, apex acute, and fruit clavate; from I. graciliflora Hooker by flower buds with a distinct awn, lower sepal mouth with an awn or appendage, less than half the length of spur in lower sepal, distal lobe long ribbon shaped, twisted and acute at apex.

Type: — INDIA. Arunachal Pradesh: Anjaw district, 10 km. before Chaglagam on the way from Hyuliang, 96°32’22.84”E, 28°15’19.47”N, 1517 m, 9 September 2012, R. Gogoi & S. Borah 21828 (holotype CAL!, isotypes ARUN!, ASSAM!)

Herbs, annual, succulent, to 120 cm tall. Stems green, basal portion terete, pink spotted, nodes swollen. Leaves alternate, simple; stipules 2, glandular, 4–5 mm long, base flat; petiole 0.5–2 cm long, glabrous, slightly winged, pink or pink spotted; lamina elliptic to narrowly elliptic, 5–18.5 × 1.5–4 cm, dorsally green with pink tinge, ventrally green, glabrous, margin crenate, base winged, apex acuminate, mid rib dorsally pink. Inflorescence axillary, 12–29 cm long, peduncle 2.5–8.5 cm, glabrous, flowers in 13–18 whorls (average 5 flowers per whorl); bracts persistent, dark pink, awl shaped, 4–5 mm long, apex glandular. Flower buds purple, shortly awned, awn dark reddish; flowers 1.5–2 cm deep, pedicels pink, 1.2–2.5 cm, glabrous. Sepals: lateral sepals 2, dark purple, awl shaped, 2–3 mm long, apex slightly glandular; lower sepal navicular, pink with darker blotches, gradually tapering to a spur, upcurved, 1.2–1.7 cm deep, mouth 0.5–0.8 cm wide, aristate, spur white with deep pink blotches, tip slightly upcurved, purple, 0.5–0.8 cm long; dorsal petal suborbicular, cucullate, pink with some darker spots, 4–5.1 × 4–5.1 mm, apex rostellate; lateral united petals pink, whitish at the base, 1.4–2 cm long (whole), bilobed, basal lobe sub-orbicular, margin crispate, 4–5 × 4–5 mm; distal lobe 1–1.4 × 0.2–0.3 cm, long-lorate, twisted, apex acute, margin crispate, auricle minute or inconspicuous; stamens to 2.5 mm long. Fruits green, clavate, 1.2–1.5 × 0.2–0.3 cm long, base purple spotted, pedicel to 2 cm long. Seeds white, 2 × 1.5 mm diam., warty.

Phenology:—Flowering and fruiting from July–September.

Distribution and habitat:—Endemic to Arunachal Pradesh. The species is only known from Chaglagam (Dalai Valley) of Anjaw district. It grows in moist places along streams at ca. 1550 m elevation.

Etymology:—The specific epithet refers to “Dalai Valley” of Anjaw district, the locality of the collection.

Conservation status:—Currently, there are three populations of altogether ca. 100 plants in the Dalai valley. According to IUCN Red List criteria (2010), the species is evaluated as Endangered (EN).

Additional collections (paratypes):— INDIA. Arunachal Pradesh: 10 km before Chaglagam on the way from Hyuliang, 6 September 2012, R. Gogoi & S. Borah 21810 (ASSAM!).

Notes:— Impatiens dalaiensis is similar to I. radiata Hooker (1875:476) and I. graciliflora Hooker (1905:15) in its general morphology and radiate nature of the inflorescence. However, Impatiens radiata differs from I. dalaiensis in exhibiting stems quadrangular and ribbed at the base, flower buds lacking an awn or appendage, flowers whitish to light purple, lower sepal mouths without an awn or appendage, distal lobes of lateral united petals non-twisted, non-lorate or ribbon-shaped, basal lobes ca. 3 x 2 mm, and fruits linear-cylindrical. In contrast to I. dalaiensis , I. graciliflora exhibits flower buds and lower sepal mouths without awns or appendages, spurs to 1.9 cm long, and distal lobes of lateral united petals short, to 5 mm, non-lorate or non ribbon-shaped.

Figures

FIGURE 2. Impatiens dalaiensis (A–G), I. radiata (H–N), and I. graciliflora (O & P). A. habit; B. basal portion of stem; C. flower bud with awn or appendage; D. frontal view of flower; E. lateral united petals; F. lower sepal with prominent awn or appendage at mouth; G. clavate shaped fruit; H. habit; I. basal portion of stem; J. flower bud without awn or appendage; K. frontal view of flower; L. lateral united petals; M. lower sepal without awn or appendage at mouth; N. linear cylindrical shaped fruit; O. habit; P. frontal and lateral view of flower. Photos by the authors, except O & P by Dr. N. Odyuo.

FIGURE. 1. Impatiens dalaiensis: A. habit; B. inflorescence; C. lateral view of flower; D. portion of succulent stem; E. floral bracts, base of pedicel; F. frontal view of flower; G. lateral sepals; H. lower sepal (lip); I. dorsal petal (dorsal & ventral view); J. lateral united petals (ventral view); K. lateral united petals (dorsal view); L. stamens; M. clavate fruit; N. seeds. Photos by the authors.