Zingiber inodorum L.Bai, Qing L.Wang, L.X.Yuan and H.Tang

Wang, Qing-Long, Yuan, Lang-Xing, Tang, Huan & Bai, Lin, 2024, Zingiber inodorum (Zingiberaceae: Zingiberoideae), a new species of Z. sect. Cryptanthium from Hainan, China, Phytotaxa 653 (3), pp. 281-289 : 282-285

Zingiber inodorum L.Bai, Qing L.Wang, L.X.Yuan and H.Tang , sp. nov. ±味姜 ( Figs. 1–2 ).

Type:— CHINA, Hainan Province, Baoting County, Qixian Mountain, under the woods by the valley stream, elev. 412 m, 18°42’38.5”N, 109°41’10.7”E, 9 August 2023 (fl.), Q.L. Wang 20230809012 (holotype: IBSC (barcode 1017723)!, isotype ATCH!).

Diagnosis. Similar to Z. guangxiense in shape of bracts and labella, and the colour of labella and lateral staminodes, but differs by the shape and size of lateral staminodes (ligulate and 10–12 × 2–3 mm in Z. inodorum vs narrowly ovate and ca. 19 × 5 mm in Z. guangxiense ). Also, in Z. inodorum each leafy shoot possesses only 4–7(–9) laminae which are broad (6–16.5 cm), prominently plicate, pale green below and have petioles 15–40 mm long (including the pulvini and narrowed bases of laminae). By contrast, in Z. guangxiense each leafy shoot often possesses 11–20 laminae which are 5–10 cm wide, flat or slightly plicate and often tinged purple below, and the petioles are 1–10 mm long and consist of pulvini only. The rhizomes of Z. inodorum are not in a single plane with each rhizome unit appearing in a lateral position in relation to its antecedent rhizome unit, while the rhizome units of Z. guangxiense are arranged in a vertical plane.

Description. Rhizomatous herbs 40–70 cm tall, leafy shoots occurring singularly or 2–3(–4) forming small loose clumps. Rhizomes not compact, pale brown externally, cream internally, almost odorless, rhizome units aligned in a lateral position relative to its antecedent units; vegetative rhizome units obconical, curved upwards, 3–3.5 cm long, 1– 1.5 cm in diam. at apex, narrowed to ca. 0.8 cm in diam. at base, with 5–6 internodes per unit, upper internodes to 1 cm long, basal internodes shorter; buds present on all the nodes of the rhizome unit, but often only one from each rhizome unit developing into a new shoot, others remaining inactive; flowering rhizome units much smaller, cylindrical, ca. 1 cm long and 0.6 cm in diam. Leafy shoots slightly arching, with 4–7(–9) laminae, approximately basal 1/2 of pseudostem leafless; bladeless sheaths 2–3, 6.5–28.5 cm long, inconspicuously longitudinally striate, greenish purple or green, densely villous; leaf sheaths inconspicuously longitudinally striate, light green, densely villous. Ligules emarginate to bilobed, 6–8 mm long, light green, densely villous (hairs yellowish), lobes obtuse; petioles 1.5–4 cm long, including a prominent, light green, 0.8–1.5 cm long pulvinus at the base, densely golden villous to glabrescent; laminae elliptic to obovate-elliptic, 18–37 × 6.5–16.5 cm (length: width ratio 2.2–3.6), adaxially green, prominently plicate, glabrous except slightly villous along the mid-vein, abaxially pale green and densely villous, apex acuminate, base obtuse to attenuate with narrow wing-like leaf margins gradually extending along the petiole/pulvinus. Inflorescences 1–2 per clump, arising from rhizome, 9–20 cm long, with 1–2 flowers opening at a time; peduncles fully subterranean, 2.5–17 cm long, covered by 4–6 sheathing bracts which are white with red tinge, glabrous adaxially, pubescent abaxially, basal ones broadly triangular-ovate, upper ones ovate; spikes ovoid to oblongoid, 5–6.5 × 1.2–3 cm, with 10–25 fertile bracts, each subtending a single flower; bracts narrowly ovate to narrowly oblong, rolling into a tube, white with purplish-red tinge, 45–56 × 6–8 mm, abaxially pubescent, apex attenuate; bracteoles narrowly ovate, rolling into a tube, 2.8–3.3 cm long, ca. 5 mm wide at base, abaxially pubescent. Flowers exserted from bracts, 7–9 cm long; calyx tubular, 15–17 mm long, 3–4 mm in diam., white, externally puberulous, apex with three blunt teeth; floral tube narrowly cylindrical, slightly widening at apex, 34–40 mm long, ca. 4 mm in diam. at apex and 2.5 mm in diam. at base, cream-white, externally glabrous, internally glabrous at base but sparsely pubescent near the throat; dorsal corolla lobe triangular-ovate, 27–29 × 5–7 mm, pale white with semi-translucent veins, abaxially pubescent, apex acute, tinged purple, shortly mucronate, mucro ca. 3 mm long; lateral corolla lobes narrowly triangular-ovate, 24–25 × 5–6.5 mm, pale yellow with semi-translucent veins, abaxially pubescent, apex acute; labellum narrowly ovate with obtuse apex, 24–26 mm long, 5–6 mm at widest point near the middle of labellum (11–13 mm broad inclusive of lateral staminodes), cream-white at base, the rest purple to purplish red, sometimes with cream striation near the throat of the flower, glabrous; lateral staminodes ligulate with obtuse apex, 10–12 × 2–3 mm, white with semi-translucent veins, sometime tinged pink at apices, glabrous, adnate to labellum in basal 1/3–1/2; stamens 16–18 mm long; anthers 14–16 mm long, anther appendages purple or red, glabrous; anther thecae 11–12 mm long (when stretched), dehiscing along their entire length. Ovary cylindrical, 6–7.5 × 2.8–3.5 mm, cream-white, pubescent (hairs rusty coloured), trilocular with axile placentation; style filiform, white, glabrous; stigma slightly thicker than style, funnel-shaped, 1–1.5 mm long, white, ostiole ciliate. Fruits ovoid-ellipsoid, 26–33 × 21–26 mm, obtusely 3-angled, pilose, pale pink externally, dehiscent along the dorsal suture into three valves when mature; valves 26–33 × 12–16 mm, scarlet red internally. Seeds 4–6 per locule, ovoid to oblongoid, 5–8 × 3.5–4 mm, black; aril sac-like, white, nearly fully covering the seeds.

Additional specimens examined (paratypes):— CHINA. Hainan Province, Baoting County, Qixian Mountain (the type locality), 17 January 2024 (fr.), Q.L. Wang 20240117002 (ATCH, HITBC, KUN).

Distribution:— Zingiber inodorum is currently known only from its type locality. An examination of specimens of Zingiberaceae at major Chinese herbaria (GXMG, GXMI, HITBC, IBK, IBSC, KUN, NAS and PE) and two herbaria in Vietnam (HN and VNMN), as well as digital images of specimens provided in the National Specimen Information Infrastructure ( Institute of Botany 2024, continuously updated) failed to locate any additional occurrences of the species.

Ecology & Phenology:— Zingiber inodorum is known from moist, shady habitats associated with a stream within primary and secondary tropical broadleaved forest. The elevation of occurrence is between 350 m to 420 m. It flowers from July to August. Fruits start to mature in August and mature fruits persist on the plants until early January of the following year. Based on observations of the first and second authors, it is suspected that this may be a nocturnalflowering species. Fully opening flower was observed at 7 pm and flowers start to wither at ca. 10 am. Nocturnalflowering species has been reported in several other genera in Zingiberoideae, e.g. Curcuma Linnaeus (1753: 2) , Hedychium J. Koenig (1783: 61) , Kaempferia Linnaeus (1753: 2) ( Leong-Škorničková et al. 2015, Nopporncharoenkul & Jenjittikul 2017, Jenjittikul & Ruchisansakun 2020, Ashokan et al. 2022), but is so far not known to occur in Zingiber . It is not known what pollinates the species.

Conservation status:— Zingiber inodorum occupies a very restricted geographic area. To data only about 68 individuals have been found and these occurred over a distance of about 1 km along a creek. We propose therefore to treat the species as ‘Critically Endangered’ (CR; D) according to the latest IUCN Criteria ( IUCN Standards and Petitions Subcommittee 2017, Standards and Petitions Committee of the IUCN Species Survival Commission 2022). Nevertheless, further field research is necessary to better-assess plant numbers and to determine possible threats to them.

Etymology:— The species epithet is derived from the Latin inodorus (meaning ‘without smell, scentless’ ( Stearn 1992)), a reference to the fact that the crushed leaves and rhizomes do not have a discernable aroma like that which occurs in many species of Zingiberaceae (although they do possess a rather faint general plant smell, like that which occurs in plants of Costaceae ).

Notes:— An unpublished phylogenetic study shows that Z. inodorum is related to a group of species that is here informally named as “ Z. cochleariforme group”. This group includes at least 11 currently recognised species, distributed in northeast India, northern Indochina, northern Myanmar and southern China. The inflorescence and the flower of Z. inodorum are most similar to those of Z. guangxiense Fang (1980: 226) , a species that was described based on material collected in Guangxi Province, China (Fang, 1980) but is now known to also occur in several provinces in south and southeast China, viz. Guangdong, Hunan and Jiangxi Provinces (unpublished data). The major differences between Z. inodorum and Z. guangxiense are found in their vegetative parts, including rhizomes (see diagnosis for details). The shape and colour of labella and lateral staminodes of Z. inodorum are also similar to Z. bipinianum D.K.Roy, D.Verma, Talukdar & Dutta Choud. in Talukdar et al. (2015: 298). However, Z. bipinianum is a species that is only known from Northeast India. The two species are rather dissimilar in other characters. Zingiber bipinianum has bracts that are much broader (2.2–2.6 cm wide) and imbricating, and its leaves are shorter and much narrower (11.5–25.5 × 6.5–10.0 cm) and petioles are only 0.3–0.5 cm long and consist of pulvinus only. Zingiber inodorum is also similar to Z. cornubracteatum Triboun & K. Larsen in Triboun et al. (2014: 60) and Z. vuquangense N.S. Lý in Lê et al. (2019: 297) in having long petiole that consists of a pulvinus and the narrowed base of lamina. By contrast, the petiole in other species in the group is short and consists of pulvinus only. Zingiber cornubracteatum differs from Z. inodorum by having much more numerous laminae per leafy shoot (20–23), and the apices of bracts being acuminate and incurved, while Z. vuquangense differs by longer ligules (1.2–3 cm), and the apices of bracts being acuminate and incurved. A key to currently recognised species of the “ Z. cochleariforme group” is provided below. However, it is noted that the characters status for species that does not occur in China are mainly based on protologues. A revision of this group is urgently needed. Zingiber kawagoi Hayata (1921: 35) was recently treated as a synonym of Z. pleiostachyum Schumann (1904: 185) by Lin et al. (2022) and Z. larsenii Theilade (1999: 404) was treated as a synonym of Z. recurvatum Tong & Xia (1987:470) by Bai et al. (2024).

Figures

FIGURE 1. Zingiber inodorum. A–B. Habit, showing that leafy shoots form small clumps and each leafy shoot often supports only 4–7 laminae. C. A plant showing the lamina shape, long petiole (lower left) and densely pubescent ligules (lower middle and right). D. An inflorescence that is half immersed in soil, with a flower beginning to wither (photographed at 10 am). E. Rhizomes, showing that the rhizome units are not aligned in a single plane (each rhizome unit appears in a lateral position relative to its antecedent rhizome unit), internal colour of rhizome (upper right) and internal colour of root tuber (lower right). D is based on Q.L. Wang 20230809012, A–C & E are based on Q.L. Wang 20240117002. Photos:A–D by Q.L. Wang, E by L. Bai.

FIGURE 2. Zingiber inodorum. A. Inflorescences and flowers (apical view: a; side view: s). B. Single flower within its bract (a) with dissection showing flower parts: bract (b), bracteole (c), calyx (d, broken laterally), dorsal corolla lobe (e), two lateral corolla lobes (f & g), labellum with lateral staminodes basally adnate (h), upper part of floral tube with stamen and stigma (i, adaxial view), ovary with two epigynous glands (j). C. A dehisced fruit with seeds. E. A dehisced fruit showing the shiny scarlet valves. E. Seeds almost totally covered by white arils and a seed with aril removed. A & B are based on Q.L. Wang 20230809012, C–E are based on Q.L. Wang 20240117002. Photos: Q.L. Wang.