Phytotaxa 464 (1): 069–076 ISSN 1179-3155 (print edition) https://www.mapress.com/j/pt/ PHYTOTAXA Copyright © 2020 Magnolia Press Article ISSN 1179-3163 (online edition) https://doi.org/10.11646/phytotaxa.464.1.5

Description of the a Peliosanthes curviandra () from Vietnam with focus on androecium structure and leaf micromorphology

NIKOLAY A. VISLOBOKOV1,2,5*, MIKHAIL S. ROMANOV3,6, EVGENIYA A. KUZMICHEVA4,7, SVETLANA P. KUZNETSOVA2,8 & ANDREY N. KUZNETSOV2,4,9 1 Department of higher , Biological faculty, M.V. Lomonosov Moscow State University, 1, 12, Leninskie Gory, 119234 Moscow, Russia. 2 Joint Russian-Vietnamese Tropical Scientific and Technological Center, Cau Giay, Hanoi, Vietnam. 3 N.V. Tsitsin Main Botanical Garden of the Russian Academy of Sciences, 4, Botanicheskaya, 127276 Moscow, Russia. 4 A.N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences, 33, Leninsky, 119071 Moscow, Russia. 5 �[email protected]; https://orcid.org/0000-0003-0568-6542 6 �[email protected]; https://orcid.org/0000-0003-1034-4563 7 �[email protected]; https://orcid.org/0000-0001-9916-4109 8 �[email protected]; https://orcid.org/0000-0002-7610-5058 9 �[email protected]; https://orcid.org/0000-0001-5595-1039 *Author for correspondence: �[email protected]

Abstract

Peliosanthes curviandra is described and illustrated as a new species from southern Vietnam. The new species is characterized by the unusual androecium comprising three erect and curved stamens, perfectly inferior ovary, and a slender tortuous style. The results of observations on the androecium structure and micromorphology of leaf blades were also presented, and the data obtained were briefly discussed in comparison with those known for some other congeners.

Keywords: androecium, leaf epidermis, , Neolourya, Ophiopogon

Introduction

Peliosanthes Andrews (1808: 605) is a of herbaceous plants which inhabit forests of tropical Asia, including part of China and India as well as southeast Asia (Jessop 1976, Averyanov et al. 2015, 2016a, 2016b, Roy et al. 2017a, 2017b, Nong et al. 2019, Taram et al. 2020). Diversity within the genus is a matter of debate: Jessop (1976) considered 33 taxa of Peliosanthes as synonyms of a single species, namely P. teta Andrews (1808: 605). Nevertheless, many safely distinguishable species of Peliosanthes have been recently described (Averyanov et al. 2015, 2016a, 2016b, Vislobokov 2016, Vislobokov et al. 2018). Features of leaf micromorphology can help the identification of species within two genera closely related to Peliosanthes, such as Ophiopogon Ker Gawler (1808: t. 1063) (Cutler 1992) and Liriope Loureiro (1790: 200) (Karpun et al. 2015). We propose that they may be also useful for the identification of closely related species within Peliosanthes, despite being still insufficiently explored. Within Peliosanthes, there is a group of species which were at first described as a separate genus Neolourya Rodriguez (1934: 96): N. weberi Rodriguez (1934: 97), N. pierrei Rodriguez (1934: 97) and N. thailandica Larsen (1966: 196). The main distinguishing feature of these species is a slender tortuous style with the stigma positioned above the level of anthers (Rodriguez 1934). The ovary of Neolourya is completely inferior (Rodriguez 1934), whereas it is half-inferior or superior in many species of the genus Peliosanthes (Averyanov & Tanaka 2012, Vislobokov et al. 2018, Nong et al. 2019). Currently, these species are considered to fall within Peliosanthes (Tanaka 2004, 2019) and were all reduced to synonyms of P. weberi (L.Rodr.) Tanaka (2004: 362). Recently described species P. triandra Aver. & N. Tanaka in Averyanov et al. (2014: 18) and P. choriandra Aver., N. Tanaka & K.S. Nguyen in Averyanov et al. (2017: 699) also belong to this group of species formerly placed under Neolourya. In the present paper, a new species named P. curviandra, which belongs to this group, is described and illustrated.

Accepted by Giovanni Astuti: 12 Aug. 2020; published: 14 Oct. 2020 69 Material and methods

Living plants as well as herbarium specimens of Peliosanthes were collected within the framework of the Joint Russian- Vietnamese Tropical Scientific and Technological Center in 2019. The in question was cultivated in the Main Botanical Garden of the Russian Academy of Sciences (Moscow). All photographs were taken from living plants in cultivation. The description is based on 10–15 measurements of each character performed using a vernier caliper and a ruler under a stereo microscope. For investigation of leaf micromorphology, 18 species of Peliosanthes were examined. The specimens were collected from plants in cultivation in the Main Botanical Garden of the Russian Academy of Sciences (Moscow) and Botanical Institute of the Russian Academy of Sciences (Saint Petersburg) (Table 1). The material was fixed in 70% ethanol and transferred to 100% acetone after passages in 80% and 96% ethanol and a 1:1 mixture of 96% ethanol and 100% acetone. Then the material was dried at the critical-point in a Hitachi HCP-2 critical point drier using liquid carbon dioxide. Dried samples were mounted onto stubs using double-sided sticky tape, coated with gold using an Eiko IB-3 ion-coater and observed using a CamScan 4DV scanning electron microscope (SEM) at Moscow State University (Moscow, Russia).

Table 1. Traits of abaxial leaf surface of Peliosanthes examined by SEM. Accession number of Greenhouse hosting Abaxial surface of leaf Species Country of origin specimens specimens* epidermis P. argenteostriata Vietnam 1319 BIN smooth P. curviandra Vietnam 19208 MBG smooth P. cambodiana Vietnam 2017.13515 MBG smooth P. cambodiana Cambodia 12608 BIN smooth P. campanulata - 264368 BIN smooth P. densiflora Laos 1317 BIN smooth P. grandiflora Vietnam 712 BIN smooth P. griffithii Vietnam 13393 BIN smooth P. irinae Laos 1304 BIN smooth P. kenhillii Vietnam 13276 BIN smooth P. labroyana - BG18PL01 BIN smooth P. longicoronata Vietnam 1999.13445 MBG smooth P. macrostegia Vietnam 88-48 BIN smooth P. retroflexa Vietnam 9314 BIN smooth P. serrulata Cambodia 12610 BIN slightly rugose P. sinica Vietnam XS14PSP01 MBG finely rugose P. teta Vietnam 13282 BIN smooth P. triandra Cambodia 12609 BIN slightly rugose P. violaceae Thailand 2018.14667 MBG slightly rugose * BIN: Botanical Institute of the Russian Academy of Sciences. MBG: Main Botanical Garden of the Russian Academy of Sciences (MBG).

Description of the new species

Peliosanthes curviandra Vislobokov, sp. nov. (Figs. 1, 2c)

Similar to P. triandra, but filaments not flashy and partly free, also similar to P. choriandra, but with three stamens curved, so that their anthers face down. Type:—VIETNAM, Dong Nai province, Tân Phú district, Cát Tiên National Park, around the point 11° 26.527’, N 107° 25.876’ E, 114 m in elev., in forest, 7 Nov 2019, N.A. Vislobokov 19208 (holotype: MW!).

70 • Phytotaxa 464 (1) © 2020 Magnolia Press VISLOBOKOV et al. Herbaceous perennial evergreen plant. Rhizome short plagiotropic or ascending, Ø 4.7–5.8 mm. Cataphylls papyraceous, up to 5.5 cm long. Roots grey, Ø 1.6–3 mm. Foliage leaves dark green, erect, petiolate. Petiole rigid, adaxially sulcate, 23–37 cm long, Ø 2 mm. Lamina lanceolate, basally cuneate and distally acuminate, 15.5–22 cm long, 2.1–3.2 cm wide, glabrous, with 2 main secondary veins on both sides of the midvein. Surface of leaf epidermis smooth. Inflorescence a raceme, 12–13 cm tall; scape erect, 3 cm long, Ø 2.3–2.6 mm, with 5–7 greenish, lanceolate, sterile bract, 10.5–13 mm long, 2.2–3 mm wide; rachis 10 cm long, Ø 1–2.3 mm, bearing about 25 . Floral bracts green, scarious, narrowly lanceolate, 2.7–7.2 mm long, 0.9–2.4 mm wide. Flowers solitary, nutant, almost completely green, basal part (below ovary) ca. 1 mm long, cylindrical, articulated with pedicel. Pedicel 5.6–7.6 mm long, Ø 0.7–0.9 mm, basally with single narrowly lanceolate bracteole 1.6–2.5 cm long, 0.5–0.7 mm wide. Perigone campanulate, 5.8–7.1 mm long, Ø 4.8–5.5 mm; tube light green on both sides, 2.4–3.3 mm long, Ø 1.7–2.3 mm; lobes 6, arranged in two whorls, equal, light green on both sides, broadly ovate, distally acuminate, 3.1–4.2 mm long, 2.1–2.8 mm wide. Stamens 6, arranged in two whorls, on the radii of tepals; filaments green, flat, fused at the base, forming stamen ring 1.8–2 mm high, Ø 2.5–2.9 mm, free part 0.8–1 mm long and wide, filaments at the radii of inner tepals erect, filaments at the radii of outer tepals incurved so that anthers facing downward inside stamen tube; anthers small, yellowish, 0.8–0.9 mm long, introrse. Style light green, cylindrical, slightly tortuous, 1.9–2.5 mm long, Ø 0.3–0.5 mm. Stigma small, as wide as style, positioned above level of anthers of outer whorl. Ovary inferior, obconic, 3-locular, 1.5–1.9 mm high. Fruits unknown. Additional specimens examined:—Living plant in the Main Botanic Garden of Russian Academy of Sciences (Moscow), garden number: 2019.15599, collected from the type locality on 7 Nov 2019. Reproductive organs in spirit of the plant collected from the type locality on 7 Nov 2019, N.A. Vislobokov 19210. etymology:—The specific epithet refers to the unique structure of its androecium, consisting of six stamens, three of which are curved down with their anthers entirely hidden inside the coronal chamber. Flowering:—Early March in greenhouse. Fruiting:—November in the habitat. Distribution:—Currently known only from the type locality. Taxonomic relationships:—Peliosanthes curviandra resembles those species formerly placed under Neolourya in general structure of , but can be distinguished by the androecium made by six partly free stamens, with only three of them erect with exposed anthers, whereas the other three are curved downward and their anthers face inside the staminal tube. The stamens of P. choriandra form a broadly ovoid or dome-shaped, corona-like structure, but filaments are free in fully open flowers. Outer three anthers are distinctly shorter than inner three and often slightly curved (Averyanov et al. 2017). Peliosanthes curviandra can be clearly distinguished from P. choriandra by the half fused (vs. free) filaments and facing down (vs. slightly curved) outer three anthers. The androecium of P. weberi is a 6-lobed corona-like structure formed by completely fused filaments (Tanaka 2004), whereas P. curviandra possesses stamens with half free filaments. The stamens of P. triandra are completely fused in a flesh broadly ovoid corona, and three anthers are inserted on the inner apical margin of corona, whereas the other three anthers are abortive, not dehiscent, placed on the adaxial surface of the corona, facing down to the bottom of coronal chamber (Averyanov et al. 2014). Apparently, the new species is closely related to P. triandra but can be clearly distinguished from it by the partly free (vs. completely fused) and flat (vs. flesh and thick) filaments with all anthers fertile (vs. three fertile and three abortive).

Discussion

Position of stamens in Peliosanthes:—The perigone of all known Peliosanthes species consists of six tepals arranged in two whorls (Jessop 1976, Vaikos & Pai 1993). The androecium also consists of six stamens, but filaments are usually partly or completely fused forming a structure usually called corona (e.g. Jessop 1976, Averyanov et al. 2016a, Nguyen et al. 2017, Roy et al. 2017a). In some species, anthers are positioned in a single whorl, but in some other species anthers opposite to the outer tepals are situated slightly outer than those opposite to the inner tepals (Averyanov et al. 2015, 2016a, 2016b, Vislobokov 2016). Considering that the trimerous pentacyclic arrangement is typical of monocots (Remizowa et al. 2010), the androecium of Peliosanthes can be considered two-whorled and diplostemonous (with alternation of floral whorls).

a species of Peliosanthes curviandra Phytotaxa 464 (1) © 2020 Magnolia Press • 71 Figure 1. Peliosanthes curviandra. a. plant; b. leaf blade, adaxial surface; c. inflorescence; d, e. flower in front view; f. flower in lateral view; g, h. longitudinal section of flower; i. part of inflorescence. Images provided by M.S. Romanov, layout by E.A. Kuzmicheva.

72 • Phytotaxa 464 (1) © 2020 Magnolia Press VISLOBOKOV et al. Figure 2. Microphotographs (SEM) of abaxial leaf surface. a. Peliosanthes longicoronata; b. P. longicoronata, part including longitudinal vein; c. P. curviandra; d. P. irinae; e. P. sinica; f. P. triandra; g. Ophiopogon sp.; h. Liriope spicata. Scale bars = 30 µm in all figures, except in b (100 µm). Images a–g provided by N.A. Vislobokov, h by M.S. Romanov, layout by E.A. Kuzmicheva.

a species of Peliosanthes curviandra Phytotaxa 464 (1) © 2020 Magnolia Press • 73 Tanaka (2004) noted that anthers opposite to the outer tepals are often positioned lower and slightly more internally than those opposite to the inner tepals in all species of Neolourya unlike other Peliosanthes. Stamens opposite to the outer tepals are slightly curved in P. choriandra (Averyanov et al. 2017), and clearly curved in P. curviandra so that their anthers face downward inside the corona. Anthers opposite to the outer tepals also face downward inside the coronal chamber in P. triandra (Averyanov et al. 2014). Thus, stamens opposite to the inner tepals can be considered as the outer whorl of androecium. The outer whorl of stamens does not alternate with inner whorl of tepals in the same way as in the case of obdiplostemony. Obdiplostemony occurs in core eudicots (Ronse De Craene & Bull-Herenu 2016) and hitherto has not been find in the genus Peliosanthes as well as in the entire Asparagaceae family. The downward curvature of the filaments opposite the outer tepals has so far been known only in species of Neolourya, hence the trait is highly likely to be an apomorphy in Peliosanthes, suggesting that these species are a monophyletic group. However, this inference based on floral morphology should be confirmed by molecular studies in the future. Micromorphology of of leaf epidermis in the genus Peliosanthes:—Leaves of all studied species of Peliosanthes lack papillae on adaxial surface. Cells of abaxial epidermis lack papillae, except certain rows of papillae along leaf veins (Fig. 2). Epidermis of most of the studied species is smooth on both surfaces. However, P. serrulata, P. sinica, P. triandra and P. violacea have finely rugose epidermis surface on the abaxial side and less rugose on the adaxial side (Fig. 2). The genus Peliosanthes relates to the genera Ophiopogon and Liriope which are classified together within the tribe Ophiopogoneae (Dahlgren et al. 1985, Kim et al. 2010). Jessop (1976) find out that Ophiopogon has numerous papillae on the abaxial epidermis whereas Peliosanthes has no papillae on the epidermal cells. He concluded that features of epidermis can be useful to separate these genera. Cutler (1992) thoroughly studied features of leaf epidermis in Ophiopogoneae, including 26 species of Ophiopogon, five species of Liriope and just two species of Peliosanthes. He concluded that features of epidermal sculpturing and stomatal arrangement can be of great help in the identification of species in Ophiopogon (Cutler 1992). Leaves of Liriope are abaxially papillate (similar to Ophiopogon), and features of leaf micromorphology can also be used for distinction of species of Liriope (Karpun et al. 2015). The present data reveals some details and diversity in features of leaf micromorphology in the genus Peliosanthes such as presence of rows of papillae along veins and rugose surface of epidermis in some species. However, these features are not diagnostic for species identification within the genus and can be used only to distinguish Peliosanthes from Ophiopogon and Liriope.

Acknowledgements

Authors are grateful to stuff of Botanical Institute of the Russian Academy of Sciences (Saint-Petersburg) and personally to L.V. Averyanov for help in collection of specimens. We are also grateful to Giovanni Astuti (editor) and two anonymous reviewers, which helped to improve the manuscript. The fieldwork (manipulations with living plants in situ and floristic description of their habitat) was performed in the Joint Russian-Vietnamese Tropical Scientific and Technological Center and A.N. Severtsov Institute of Ecology and Evolution of RAS. The work on cultivation, investigation of flowering phenology and preliminary identification of the plant was performed by V.G. Drockina and M.S. Romanov at the Unique Scientific Installation “Fund Greenhouse” of N.V. Tsitsin Main Botanical Garden of Russian Academy of Sciences in accordance to Institutional research project № 18-118021490111-5. The morphological illustrations were designed by E.A. Kuzmicheva. Investigation of micromorphology and description of the new species were carried out by N.A. Vislobokov in Lomonosov Moscow State University and were funded by RFBR according to the research project № 18-34-20135.

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