Polypleurum chinense B.Hua Chen & Miao Zhang, 2022

Chen, Bing-Hua, Zhang, Miao, Zhao, Kai, Zhang, Xiao-Hui & Ge, Chang-Li, 2022, Polypleurum chinense (Podostemaceae), a new species from Fujian, China, based on morphological and genomic evidence, PhytoKeys 199, pp. 167-186 : 167

Polypleurum chinense B.Hua Chen & Miao Zhang sp. nov.

Figs 1 , 2 , 3 , 4

Diagnosis.

The new species can be easily distinguished from most other species, except Polypleurum longistylosum , by tufts of leaves on both sides of the root between the root branches, a more or less flattened, ellipsoid, rough capsule with a greater number of longitudinal ribs (> 12), a spathella nearly completely enclosing the ovary and stamen at anthesis, a solitary stamen and a very short capsule stalk (<2 mm). The narrower roots (0.6-0.8 mm vs.1.0-1.5 mm) with leaves 8-12 per tuft (vs. 4-8), up to 23.1 mm (vs. 5 mm) long, fewer (4 vs. 6) bracts, short spiny or glandular hairs on the spathella (vs. papillate) in the new species differentiate it from P. longistylosum (Table 1 ).

Type.

China. Fujian Province: Yunxiao County, Wushan Mountains , elevation 430 m, 117°14'E, 23°53'N, 4 January 2021, Bing-Hua Chen CBH 04407 (Holotype FNU barcode FNU0041131; isotype FNU barcode FNU0041132) .

Root creeping, adhering to rock surfaces, ribbon-like, branched, 0.6-0.8 (-1.0) mm wide, with tufts of leaves on both flanks, not associated with root branching, 2-4 mm apart; leaves 6-12 per tuft, in two ranks, to 17.6 (12.4-23.1) mm long, 0.2-0.4 mm wide, needle-like (Fig. 1 ). Flowering shoots on both flanks of root, very short; bracts 2-6, needle-like, to 5-6 mm long, caduceus. Flower just prior to anthesis, with only two remaining bracts, pale purplish-red. The anthesis begins when the water level is further reduced, the bracts disappeared, but the base remained. Flower1, bud covered by ellipsoid spathella, spathella stalk ca. 3 mm in length, coated with short spiny hairs or glandular hairs, with a papilla-like tip, the papilla ruptured near apex at anthesis, but persisting spathella base keeps the ovary and lower bottom of stigma enclosed. Pedicel ca. 0.7 mm long; tepals 2, one on each side of stamen, linear, ca. 0.3 mm long; stamen 1, up to 2.9 mm long, protruding from spathella; ovary dark green, ellipsoid, ca. 1.8 mm long, 0.9 mm wide, 1-locular, free central placenta; stigmas 2, forked near base, thin, needle-like, ca. 0.9 mm long, as long as, or slightly shorter than ovary, branched at the top, upper part exerted from spathella; ovules on marginal surface of septum, 25-35 per septum (Fig. 2 ). Post-pollination, the spathella and ovary developed into a pale ellipsoid, ca. 2 mm long, arranged on both sides of the root, the ovary stalk lengthened and developed into pedicels (ca. 0.7 mm). Mature capsule 12-14-ribbed, conspicuous under microscope, fissured longitudinally; seed yellowish-brown, with shallow groove, ca. 300 μm long (Fig. 3 ).

Distribution and habitat.

Polypleurum chinense is only known from Fujian, China (Fig. 5 ), where it grows on rocks in unpolluted streams. In addition, Cladopus austrosinensis M. Kato & Y. Kita from the same family was found on the rock surfaces in the lower reaches of the stream. Many other plants grow in the surrounding habitat, whose tree layer includes Pinus massoniana Lamb. ( Pinaceae), Ficus fistulosa Reinw. ex Bl. ( Moraceae), Casearia glomerata Roxb. ( Salicaceae), Carallia brachiata (Lour.) Merr. ( Rhizophoraceae) and planted Eucalyptus grandis x urophylla ( Myrtaceae) and others; the shrub layer includes Ficus pyriformis Hook. & Arn. ( Moraceae), Illicium dunnianum Tutch. ( Schisandraceae); the vegetation layer includes woody vine plants Melodinus suaveolens (Hance) Champ. ex Benth. ( Apocynaceae), Dendrotrophe varians (Blume) Miquel ( Santalaceae), Toddalia asiatica (L.) Lam. ( Rutaceae), Mappianthus iodoides Hand.-Mazz. ( Icacinaceae), Byttneria grandifolia Candolle ( Malvaceae), Uvaria boniana Finet & Gagnep. ( Annonaceae) and more; the herbaceous layer includes Arundina graminifolia (D. Don) Hochr. ( Orchidaceae); on the cliff, there are Cryptochilus roseus (Lindley) S. C. Chen & J. J. Wood, Pholidota chinensis Lindl., Dendrolirium lasiopetalum (Willdenow) S. C. Chen & J. J. Wood and other Orchidaceae.

Phenology.

Polypleurum chinense was observed flowering and fruiting in its habitat from December to February when the water level is reduced to partly expose the rocks.

Etymology.

The Zhong Guo Cha Pu Chao (中国叉瀑草). The specific epithet " Polypleurum chinense " refers to China, as the distribution of this genus was first identified there and it was proven to be a new species of Polypleurum .

Conservation status.

According to our investigation, Polypleurum chinense was found in patches attached to rock surfaces in rapid-flowing streams in the Wushan Mountains range in Zhangzhou City, Fujian Province, China. It is difficult to count the exact number of individuals in the population. Its habitat is vulnerable to anthropogenic destruction and projects like reservoir construction. To determine the exact distribution of this species, further fieldwork is required around the Wushan Mountains in Zhangzhou City and nearby mountainous areas. Therefore, we suggest the species be classified as category DD (Data Deficient), according to the International Union for Conservation of Nature ( IUCN 2022). According to the Updated List of National Key Protected Wild Plants (Decree No. 15) by the country’s State Forestry and Grassland Administration and the Ministry of Agriculture and Rural Affairs, all of the known genera of Podostemaceae found in China are classified in the national secondary protection list. The new recorded genus should also be included on the national secondary protection list during the upcoming revision process.

Figures

Figure 1. Polypleurum chinense A habitat B habit, showing plants (red arrow) on rock surface in rapids C plants adherent to rock surface (photo in aquarium) D roots with tufts of leaves on both flanks E tufts of 1 eaves. Scale bars: 5 mm (C); 2 mm (D); 1 mm (E).

Figure 2. Polypleurum chinense A plants in bud adhering to rock surface B ribbon-like root with young floriferous shoots on flanks C flower bud covered by spathella (s) above bracts (b) D shoots along the flanks of the ribbon-like root between the root branches E, F flower at anthesis on peduncle with ruptured spathella G spathella H flower with spathella removed, stamen, and ovary, arrow shows a tepal on side of stamen I gynoecium without bracts J ovules on ovary septum K, L, M stamen, arrows show two tepals on sides of stamen. Scale bar: 1 mm (C, F, J); 2 mm (B, E, M); 500 μm (G, H, I, K, L).

Figure 3. Polypleurum chinense A habitat in the dry season when the river level is reduced B habitat showing mature fruits C elliptic pale bodies along the flank of the root D stalked fruit, showing ribs E dehisced capsule, showing seven ribs on the half of capsule, conspicuous F dehisced capsule, showing persistent valve and seeds G seeds. Scale bars: 20 mm (B); 5 mm (C); 500 μm (D); 400 μm (E); 1 mm (F); 200 μm (G).

Figure 4. Illustration of Polypleurum chinense A ribbon-like root with tufts of leaves B flower bud covered by spathella above bracts C floriferous shoots along the flanks of the root between the root branches D flower at anthesis on peduncle with ruptured spathella E flower with spathella removed, stamen and ovary, a tepal on side of stamen F stamen G ovules on ovary septum H stalked fruit, showing ribs I seeds.

Figure 5. Geographical distribution map of Polypleurum chinense (▲). (Map constructed using ArcGis 9.2 software).