Platanthera guangdongensis Y.F. Li, L.F. Wu & L.J. Chen, 2018

Ye, Qin-Liang, Li, Yu-Feng, Zhong, Zhi-Ming, Wu, Lin-Fang, Chen, Li-Jun & Li, Ming-He, 2018, Platanthera guangdongensis and P. zijinensis (Orchidaceae: Orchideae), two new species from China: Evidence from morphological and molecular analyses, Phytotaxa 343 (3), pp. 201-213 : 207-209

Platanthera guangdongensis Y.F. Li, L.F. Wu & L.J. Chen sp. nov. (ỮṪǺḆĔ; Figs. 4 , 5 )

Type:— CHINA, Guangdong ( ỮṪ). Zijin ( ẾḮ), in a dense forests near the valley, alt. 660 m, 31 May 2017, Liu 10273 (holotype: NOCC!).

Diagnosis:— Platanthera guangdongensis is similar to P. fujianensis , from which it differs by the shorter inflorescence and fewer flowers (3.5–5.0 cm with 5–9 flowers vs. 8.0–10.0 cm with 13–18 flowers), shorter floral bract (0.6–0.9 cm vs. 1.3 cm), ovate-elliptic dorsal sepal (vs. broadly ovate), oblong lateral sepal (vs. oblong-lanceolate), ovate-elliptic petal (vs. ovate), and ligulate lip (vs. ligulate-triangular).

Herbs terrestrial, leafless, holomycotrophic. Plants 19–22 cm tall. Rootstock cylindric, fleshy, 1.3–2.5 × 2.5–3.5 cm, with many hairy appendages. Stem erect, yellowish green, with 7–8 tubular sheaths at base; sheaths 1.0–1.5 × 0.2–0.5 cm. Inflorescence racemose, 3.5–5.0 cm long, with 5–9 flowers loosely arranged; floral bracts lanceolate, 0.6–0.9 cm long, apex acute. Sepals and petals pale greenish, lip pale greenish yellow, spur pale greenish white; pedicel and ovary 1.0– 1.2 cm long. Dorsal sepal erect, ovate-elliptic, 2.1–2.5 × 1.4–1.6 mm, apex obtuse; lateral sepals oblong, oblique, 4.0–4.5 × 0.9–1.2 mm, apex obtuse. Petals ovate-elliptic, oblique, 3.2–3.6 × 1.1–1.3 mm, apex obtuse; lip ligulate, 4.0–4.3 × 1.4–1.6 mm, apex obtuse; spur pendulous, cylindric, 1.0– 1.2 cm long. Column ca. 2.0 mm; pollinia obovoid, with slender caudicles and suborbicular viscidia; stigma concave, lying directly below rostellum.

Phenology: —Flowering May.

Distribution and habitat: –– Platanthera guangdongensis is only known from Zijin country, Guangdong Province, China. It grows in a dense forest, which is mainly composed of Alpinia densibracteata ( Zingiberaceae ), Altingia chinensis ( Altingiaceae ), Ardisia punctata , Myrsine seguinii ( Myrsinaceae ), Castanopsis fissa , C. fordii ( Fagaceae ), Dalbergia millettii , Millettia dielsiana ( Fabaceae ), Ehretia longiflora ( Ehretiaceae ), Itea chinensis ( Iteaceae ), Gordonia axillaris ( Theaceae ), Rhododendron championiae ( Ericaceae ), and Woodwardia japonica ( Blechnaceae ). Other orchids, Apostasia shenzhenica , Cymbidium ensifolium , Lecanorchis nigricans , Tainia dunnii , were found growing nearby this new species.

Etymology: —The specific epithet refers to the locality of Guangdong Province where this new species has been found.

Conservation status: ––The new species was found in only two populations, each of which consisted of no more than 10 individuals. Using the World Conservation Union Red List Categories and Criteria ( IUCN, 2016), P. guangdongensis should be treated as critically endangered.

Figures

FIGURE 4. Platanthera guangdongensis Li, Wu & Chen.A. Flowering plant.B. Flower, front view. C. Flower, side view. D. Dorsal sepal, petal, lateral sepal, and lip. E. Sheath. F. Pollinarium. Drawn by Li-Jun Chen.

FIGURE 5. Platanthera guangdongensis Li, Wu & Chen. A. Habitat and flowering plant. B. Inflorescence. C. Rootstock and stem. D. Flower, front view. E. Flower, side view. F. Pollinarium. Photographs by Wen-Hui Rao.