Research Article |
Corresponding author: Bo Li ( hanbolijx@163.com ) Academic editor: Alexander Sukhorukov
© 2019 Yue-Ning Guo, Shao-Feng Chen, Ming-Lin Chen, Bo Li.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Guo Y-N, Chen S-F, Chen M-L, Li B (2019) Persicaria jucunda var. rotunda (Polygonaceae, Persicarieae), a distinct distylous taxa raised to specific rank. PhytoKeys 126: 127-138. https://doi.org/10.3897/phytokeys.126.35442
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Persicaria jucunda var. rotunda (Z.Z.Zhou & Q.Y.Sun) Bo Li was originally published in the genus Polygonum L. and treated as a variety of P. rotundum Meisn. [≡Persicaria jucunda (Meisn.) Migo]. After carefully comparing the macro- and micro-morphological characteristics of the achenes, leaf epidermis and tepals and the habitat between the variety and its typical variety, we confirmed that P. jucunda var. rotunda is clearly different from P. jucunda and should not be treated as a variety, but be raised to a specific rank as P. rotunda (Z.Z.Zhou & Q.Y.Sun) Bo Li. The species is distylous and could be easily distinguished from all other Persicaria taxa by a combination of morphological characters, such as completely decumbent leafless basal branches, almost sessile leaves, linear-lanceolate with rounded leaf bases, spicate, short and dense inflorescences, slender pedicels longer than bracts and dimorphic flowers and achenes. P. rotunda is endemic to several large wetlands of eastern China and usually occurs as one of the dominant species in some plant communities.
Distyly, micro-morphology, new combination, Polygonum, variety
Persicaria (L.) Mill., after separation from the former polyphyletic genus Polygonum L., is currently placed within the tribe Persicarieae of Polygonaceae. The genus contains approximately 150 species of annual or perennial herbs and occurs mainly in temperate and subtropical regions of the Northern Hemisphere (
Persicaria jucunda var. rotunda (Z.Z.Zhou & Q.Y.Sun) Bo Li (
The field investigations were carried out from 2014 to 2019. Fresh leaf materials and flowers of both P. jucunda and P. rotunda were collected and immediately fixed in FAA solution (formalin: acetic acid: alcohol = 18:1:1). The measurement of morphological characters was conducted based on both herbarium specimens (JXAU, acronym according to
For light microscopy (LM) observation of leaf epidermis, samples were taken from the mature leaves fixed in FAA solution, dissected under a OPTPro stereoscope (Chongqing Optec Instrument Co. Ltd., China), stained in a solution of 1% safranin, and cleaned in distilled water three times before being mounted in glycerine jelly. Observations and micrographs were conducted randomly from 5 prepared slides per species under LM. Terminology follows
For scanning electron microscopy (SEM) observations, samples of achenes were removed from mature fruits and dried in silica gel. After cleaned in 95% ethanol, mounted on to cupreous stubs and coated by JFC-1100E sputter coater (JEOL Led., Japan), samples were examined under JSM-6360LV SEM (JEOL Led., Japan) at a voltage of 25 KV. Terminology follows
≡Polygonum jucundum var. rotundum Z.Z.Zhou & Q.Y.Sun, Acta Phytotax. Sin. 45(5): 714 (713–718; figs.). 2007. Type: CHINA. Anhui Province, Dongzhi County, Shengjin Lake, on riparian plains, Alt. 6–20 m, 4 October 2006, Z.Z.Zhou 0602 (holotype: PE!, isotype: ANU).
≡Persicaria jucunda var. rotunda (Z.Z.Zhou & Q.Y.Sun) Bo Li, Phytotaxa 91 (1): 24. 2013.
This species is easily distinguished from other Persicaria taxa by its completely decumbent leafless basal branches, almost sessile leaves, truncate, linear-lanceolate leaf blades, spicate, short and dense inflorescences, pedicels longer than bracts and dimorphic flowers and achenes. It occurs as one of the dominant species of some lakeshore plant communities in several large wetlands of northern Jiangxi and south-western Anhui provinces, eastern China.
Annual herbs. Stems slender, glabrous, basal branches 6–26, completely decumbent, 3–15 cm long, leafless, dark brown, producing numerous fibrous roots at each node; 3–12 additional flowering shoots branched from the upper nodes of each basal branch, 6–65 cm high, prostrate to erect, green to purplish-red, nodes inflated, purple. Leaves nearly sessile; leaf blades narrowly lanceolate to linear-lanceolate, 1.5–12.5 cm long, 0.3–1.3 cm wide, lateral veins 9–16 pairs, both surfaces glabrous, base round, apex acuminate, margin entire, shortly ciliate. Ocrea tubular, 4.5–11.5 mm long, membranous, sparsely appressed pubescent, apex truncate, fimbriate, cilia 2.2–5.3 mm long. Inflorescence terminal, erect, spicate, dense, 0.5–3.8 cm long; peduncle 3.5–6.5 cm long, glabrous; bracts purplish-red, funnel-shaped, sparsely pubescent, margin submembranous, shortly ciliate, each bract contains 4–7-flowers. Pedicel longer than bracts, 1.5–2.5 mm. Flowers dimorphic; perianth 5-parted, pinkish-white; long-styled flowers (called as L-morph) 3.9–4.4 mm long, stamens 8, 2.6–3.2 mm, styles 3, connate to below middle, 4.3–5.1 mm, exserted; short-styled flowers (called as S-morph) 3.7–4.2 mm long, stamens 8, 3.8–4.9 mm, exserted, styles 3, connate to below middle, 2.4–2.9 mm; stigmas capitate; nectaries 8, arranged at the base of ovary. Achenes included in persistent perianth, dimorphic; L-morph dark brown, ellipsoid, trigonous, base rounded to broadly cuneate, apex acuminate, surface opaque, densely reticular - pitted, 3.6–4.2 mm long, 2.1–2.3 mm wide; S-morph black, ovoid, trigonous, base broadly cuneate, apex acute, surface opaque, densely pitted, 2.9–3.3 mm long, 1.8–2.1 mm wide.
Flowering was observed from July to December and fruiting from late July to January.
Persicaira rotunda is currently known only from several wetlands in north of Jiangxi Province and southwest of Anhui Province, eastern China and mainly grows in marshy and grassy areas around Daguan Lake, Lihu Lake, Longgan Lake, Poyang Lake Qingcao Lake, Shengjin Lake, Shimeng Lake and Wuchang Lake, which are several small to large lakes located near the Yangtze River. It usually occurs as one of the dominant species of some lakeshore plant communities (Fig.
CHINA. Jiangxi Province, Xingzi County, Shenling Lake, on grassy lakeside, Alt. 10 m, 29.270044N, 116.040173E, 16 July 2008, B.Li JX046 (IBSC); Jiangxi Province, Yongxiu County, Wucheng Town, Poyang Lake, in wet meadow, Alt. 14 m, 29.114364N, 116.032021E, 11 December 2017, B.Li LB0778 (JXAU); Jiangxi Province, Yongxiu County, Wucheng Town, Poyang Lake, in wetland marsh, Alt. 6 m, 29.133935N, 116.053571E, 15 October 2018, B.Li LB0901 (JXAU).
As noted by
Box plots of four quantitative characters, leaf length (A) leaf width (B) number of leaf lateral vein pairs (C) and inflorescence length (D) of Persicaria rotunda and P. jucunda. The boxes (rectangle region) represent the interquartile range and the whiskers (vertical line) represent the range excluding the outliers (circles). The three upper, middle and lower lines on the boxes represent the 75%, 50% and 25% of the variables, respectively. The upper and lower ends of the whiskers represent the maximum and minimum values of the variable, respectively. The circles represent the single value, where the variable value exceeds 1.5 times the difference between the 75% and 25%.
Persicaria rotunda | P. jucunda | ||
Habitat | wetlands | forest margins, grassy slopes or moist valleys | |
Branches | the primary branches completely decumbent, leafless and the secondary branches prostrate to erect | ascending to erect, without leafless branches | |
Leaves | Petiole | nearly absent | 3–6 mm long |
Shape | narrowly lanceolate to linear-lanceolate | lanceolate or elliptic-lanceolate | |
Lateral veins (pairs) | 9–16 | 6–10 | |
Adaxial epidermis | polygonal epidermal cells with straight anticlinal walls no stomata no glands | irregular epidermal cells with straight to curved anticlinal walls stomata mostly anisocytic or occasionally paracytic sparse two-celled peltate glands | |
Abaxial epidermis | irregular epidermal cells with curved to sinuolate anticlinal walls stomata anisocytic plenty of four-celled peltate and spheroidal glands | irregular epidermal cells with sinuolate to sinuate anticlinal walls stomata paracytic no glands | |
Length of Inflorescences (cm) | 0.5–3.8 | 1.0–8.2 | |
Tepals | Length (mm) | L-morph 3.9–4.4, S-morph 3.7–4.2 | L-morph 2.8–3.3, S-morph: 2.7–3.2 |
Epidermis | anticlinal walls of epidermal cells curved to sinuolate 10–14 sinuate striates on cuticular layer | anticlinal walls of epidermal cells sinuolate to sinuate 12–18 straight to sinuolate striates on cuticular layer | |
Achenes | Size (length × width, mm) | L-morph 3.6–4.2 × 2.1–2.3, S-morph 2.9–3.3 × 1.8–2.1 | L-morph 2.1–2.6 × 1.6–1.8, S-morph 2.2–2.7 × 1.7–1.9 |
Surface | opaque, densely pitted | shiny, smooth | |
Epidermal ornamentations | reticulate | Indistinctly reticulate |
Besides the differences summarised by
Though both of P. rotunda and P. jucunda have dimorphic flowers, the achenes of P. rotunda are also dimorphic, with the L-morph ellipsoid in shape and dark brown in colour, whereas the S-morph achene is ovoid in shape and black in colour (Fig.
Achene morphology of Persicaria rotunda A dimorphic achenes under a stereoscope B–C SEM micrograph of L-morph achene B whole view C partial view showing its epidermis sculpture D–E SEM micrograph of S-morph achene D whole view E partial view showing its epidermis sculpture. Scale bars: 500 μm (B, D); 50 μm (C, E).
Leaf epidermis characters have been tested to be of important taxonomic significance in Persicaria (
In the protologue,
The authors are grateful to Ms. Yun-Xiao Liu for the line-drawing illustrations, to Ms. Xiao-Ying Hu for technical assistance with SEM observation and to Dr. Xin-Xin Zhu for providing some photos of Persicaria jucunda. This work was supported by the National Natural Science Foundation of China (grant no. 31660047) and Natural Science Foundation of Anhui Province (grant no. 1808085MC76).