Impatiens jenjittikuliae Ruchis. & Suksathan

Ruchisansakun, Saroj & Suksathan, Piyakaset, 2019, Impatiens jenjittikuliae (Balsaminaceae), a new species from Thailand, PhytoKeys 124, pp. 139-147: 140-145

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Impatiens jenjittikuliae Ruchis. & Suksathan

sp. nov.

Impatiens jenjittikuliae Ruchis. & Suksathan  sp. nov. Figs 1View Figure 1, 2View Figure 2, 3View Figure 3, 4View Figure 4, 5View Figure 5


Impatiens jenjittikuliae  is most similar to I. lacei  Hook.f. It differs from I. lacei  by its densely pilose lateral sepal (versus glabrous) and by having no long hairs along its lamina margin (versus distinct long hairs especially along the lower-half of leaf margin).


THAILAND. Tak Province, Thasongyang District [17°30'1"N, 98°3'60"E], limestone area near waterfall in mixed deciduous forest at 540 m alt., 20 October 2018, S. Ruchisansakun 900 (holotype: QBG; isotypes: BK, BKF, Mahidol University Herbarium)


Lithophytic, annual herb, up to 6-30 cm tall. Stem erect, up to 1.2 cm in diam., cylindrical, branched, green, densely pilose with short white hairs. Leaves spirally arranged. Petiole 3-7.5 cm long, ca. 2.5 mm in diam., pale green to green to pink, pilose; with 5-7 pairs of long hairs on petiole, up to 2 mm long, green, sometime with red tips. Lamina 9-20 × 3-7 cm, ovate to elliptic, apex acute, base cuneate, margin shallowly serrate, adaxial green, abaxial pale green, pilose on both sides; lateral veins 10-12 pairs. Inflorescence raceme, axillary, 8-12 florets; peduncle 7-10 mm long, 1.5-2 mm in diam., pale green, densely pilose; rachis 8-20 mm long, ca. 1.5 mm in diam., pale green, densely pilose, hairs shorter than those on peduncle. Flowers ca. 20 × ca. 15 mm, ca 3 mm deep, pinkish white with reddish purple lip. Bracts ca. 1 × 0.5 mm, linear to narrowly lanceolate, apex acute, base cuneate, green, caducous, abaxial densely pilose with white hairs. Pedicel 12-15 mm long, less than 1 mm in diam., pink, densely pilose with white hairs. Lateral sepals 2, 5-6 × 6-7 mm, free, broadly ovate, the apex mucronate, the base truncate, pale pink, abaxially densely pilose with white hairs. Lower sepal 11-13 × 8-10 mm, ca. 14-17 mm deep, broadly navicular to subsaccate, apex acuminate and mucronate, white with green tip, densely pilose to strigose outside with long white hairs, distal part gradually constricted into a curved spur, 14-15 mm long, white to pale pink. Dorsal petal 11-12 × 14-15 mm, broadly ovate to obcordate, cucullate, apex emarginate and mucronate, base cordate, white to pale pink, densely pilose with white hairs, abaxial midvein with a white crescent-shaped crest, 1-1.5 mm high. Lateral united petals 20-24 mm long, free: the upper petals 9-10 × 10-11 mm, broadly oblong, apex truncate, base cuneate, upper outer part white to pale pink, lower inner part dark purple; the lower petals 17-19 × 8-10 mm, oblong, apex truncate, pink to reddish-purple; with a pink auricle at the base, ca 1 mm high. Stamens 5; filaments 4-5 mm long, white; anthers white. Ovary ca 4 mm long, 1.5-2 mm in diam., short fusiform, 5-carpellate, green, glabrous. Fruits, short fusiform capsule, 11-12 mm long, 6-8 mm in diam., subglobose, 5-lobed, green, glabrous. Seeds ca. 20 per fruit, ca. 1.34 mm long, ovoid, brown.

Pollen morphology: Pollen grains 4-colpate (Fig. 3AView Figure 3). Equatorial view oblong, ca 35 × 18-19 μm (length/width = 1.89); Polar view nearly elliptic, ca. 17 μm thick, colpi four, linear, ca 9-10 μm (Fig. 3AView Figure 3); surface entirely covered with numerous irregular lumens, 1.2-2 μm diam, lumens deep, sparsely granulate (Fig. 3BView Figure 3); muri slightly straight, joint of muri slightly corniculate (Fig. 3CView Figure 3).

Seed morphology: Brown ovoid, ca 1.34 × 0.93 mm, ca 0.51 μm thick (length/width = 1.44) (Fig. 4View Figure 4). Seed coat a composite of two types, thick finger-like cells, and inflated cells with granulate walls (Figs 4C, DView Figure 4).

Stem anatomy: Stem herbaceous, without lignification (Figs 5 A–CView Figure 5). Only angular collenchyma for stem-strengthen were found (Fig. 5DView Figure 5).


Flowering from Oct. to Nov.; fruiting Oct. from Nov.


The new species is only known from the type locality in Tak Province, Thailand.


Impatiens jenjittikuliae  grows on limestone close to waterfall in a mixed deciduous forest, 520-600 m elevation (pers. obs.).

Proposed IUCN conservation assessment.

Critically Endangered B1ab (i, ii, iii) + 2ab (i, ii, iii). This species is only known from the type locality; the extent of occurrence is estimated to be less than 5 km, where it occurs as a small population ( IUCN 2012).


The new species is named in honor of Dr. Thaya Jenjittikul who encouraged the first author to step in and study this lovely plant family.

Pollination ecology.

The author observed five visitations by bees from the family Apidae  (identified by an entomologist, Pornpimon Tangtorwongsakul) during the expeditions. The size of bee body fit well with the floral entrance (Fig. 6View Figure 6). Moreover, the floral structure of this new species is similar to other bee-pollinated species, e.g. I. psittacina  ( Ruchisansakun et al. 2016). Hence, we concluded that it is a bee-pollinated species.