Impatiens shiyomiensis Hareesh & M.Sabu, 2020

Hareesh, Vadakkoot Sankaran & Sabu, Mamiyil, 2020, Two new balsams (Balsaminaceae) from Eastern Himalayas, India, Phytotaxa 437 (5), pp. 291-300 : 294-297

2. Impatiens shiyomiensis Hareesh & M.Sabu sp. nov. ( Figs. 3 , 4 )

The new species is morphologically similar to I. rugosipetala , but differs from the latter in having erect inflorescence (vs. pendent), white flowers with yellow throat (vs. brick red or reddish with yellow throat and margins), glabrous petals (vs. rugose) and clavate capsule (vs. linear). It also shows similarities with I. drepanophora but differs in having acute bract apex (vs. aristate with 2–3 mm long awn), obliquely-ovate to triangular lateral sepals with acuminate apex (vs. ovate-falcate, apex aristate with 3 mm long curved awn) and lorate distal lobe of lateral united petals (vs. oblong to dolabriform) ( Table 2).

Type:— INDIA. Arunachal Pradesh: Shi-Yomi district, 7 km away from Siko Dido Water fall towards Mechuka, ± 1200 m, N 28° 30’ 8.82”, E 94° 24’ 51.07”, 19 September 2019, M. Sabu & V. S. Hareesh 158764 (holotype CAL!, isotypes, CAL!, MBGH!)

Terrestrial non-succulent herbs, 25–40 cm long; stem branched, sub-terete or rarely minutely ridged, pale green, glabrous; internodes 1–2.5 cm long, pale pinkish-green at base and pale green towards the apex, glabrous; nodes swollen when mature. Leaves alternate at distal part and spirally arranged proximally along the stem, petiolate; lamina 2.5–12 × 2–8.5 cm, ovate or elliptic, caudate-acuminate at apex, crenate at margin, crenations apiculate, cuneate at base, dark green above and pale beneath, glabrous on both sides; lateral nerves 5–9 on each side of the mid-vein, abaxially prominent; petiole 1–2.5 cm long, slender, slightly winged, pale green, glabrous; petiolar glands rare, subulate, pale green, glabrous. Inflorescence axillary raceme, 5–7-flowered; peduncle 8–10 cm long, glabrous; bract ca. 2 × 2.5 mm, ovate, acute at apex, pale green, glabrous, caducous. Flowers white with yellow throat; pedicel 10–14 mm long at flowering and elongates up to 15–17 mm long in fruiting stage, pale green, glabrous; lateral sepals 2, 2–2.5 × ca. 0.8 mm, obliquely-ovate to triangular, apex acuminate, transparent or pale green with pale pink coloration towards the apex, glabrous; dorsal petal 10–12 × 10–11 mm, orbicular, apex shallowly emarginated, white, glabrous; lateral united petals 23–27 × 5–5.5 mm, 2-lobed, white with yellow throat; basal lobe 6–7 × 5–5.5 mm, obovate to triangular, yellow with white towards the margins; distal lobe 17–20 × 1.5–2 mm, lorate, twisted, rounded or obtuse at apex, white; dorsal auricle inconspicuous, deep yellow; lower sepal 15–18 × 5–7 mm at mouth, navicular, apex with ca. 6 mm sharp beak, white, faced straight in floral bud and re-curved and faced parallel to the lower sepal in flowering stage, glabrous; spur 12–15 mm long, cylindrical, apex entire, deeply outwardly curved, white, glabrous. Column 3.5–4 × 1.5–2.5 mm, slightly bent towards the apex; filaments ca. 2 × 1 mm, white, glabrous; anthers ca. 1.5 × 2–2.5 mm, yellow, glabrous. Pistil ca. 2.5 × 1 mm; ovary ellipsoid, pale green, glabrous. Capsule 11–14 × ca. 2 mm, clavate, green, glabrous; seeds ca. 2 × 1.5 mm, obovate, cream.

Phenology:— August to October

Etymology:— The specific epithet named after Shi-Yomi District, one of the newly formed district in Arunachal Pradesh, type locality of the taxon.

Habitat and distribution:—The new species known only from type locality, 7 km from Siko Dido Water fall towards Mechuka, Shi-Yomi District of Arunachal Pradesh. Populations were observed moist areas near the streams at an altitude of around 1200 m a.s.l. During our expedition, we observed only three populations with more than 30 mature individuals. At present, the new species faces no serious threat. However, road broadening may affect the natural habitat, which would result in the decrease in number of Individuals ( IUCN 2001). Further conservation measures are needed.

Note:— Impatiens drepanophora is one of the widespread balsams distributed in the Eastern Himalayan regions of China, India, Myanmar and Nepal. Though, the flowers show variations in the colour patters, certain floral characters such as the presence of prominent awn on the apex of bracts, lateral sepals and lower sepal (falcate) are constant. Yellow coloured flowers are common throughout the Himalayas ( Figs. 5 ). However, white coloured forms are also reported form Myanmar ( Ruchisansakun et al. 2018) and pale purple forms from China ( Yu 2012). During the expeditions in Arunachal Pradesh, we noticed purple forms of I. drepanophora which occur towards Along from Mechuka ( Figs. 6 ). The entire plant (both vegetative and reproductive) shows maximum similarities with the yellow forms except in the moderate curvature of the lateral sepal’s awn ( Figs. 6 E & H ).

Figures

FIGURE 3. Impatiens shiyomiensis. Habitat. Photos by V.S. Hareesh.

FIGURE 4. Impatiens shiyomiensis. A. Habit. B.. Flower side view. C. Flower front view. D. Lateral sepal adaxial view. E & F. Dorsal petal (adaxial and abaxial view). G & H. Lateral united petals (adaxial and abaxial view). I. Lower sepal with spur. J. Column showing stamen and carpel. K. immature capsule. L. Capsule (mature). Photos by M. Sabu & V.S. Hareesh.

FIGURE 5. Impatiens drepanophora (Yellow form).A.Habit.B.Arrow mark indicating prominent awn on bract.C.Arrow mark indicating curved awn on the lateral sepals of the inflorescence. Photos by V.S. Hareesh.

FIGURE 6. Impatiens drepanophora (Pale purple form).A. Habit. B. Inflorescence. C. Bracts. D & G. Dorsal petal (adaxial and abaxial view). E & H. Lateral sepal (adaxial and abaxial view). F & I. Lateral united petals (adaxial and abaxial view). J. Lower sepal with spur. K. Column showing stamen and carpel. L. Capsule (mature). Photos by M. Sabu & V.S. Hareesh.