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13Gymnomitrion fissum (Gymnomitriaceae, Marchantiophyta) — a new species with fissured leaf surface from China
A. D. Potemkin1, Yu. S. Mamontov123, N. S. Gamova4
1 Komarov Botanical Institute, Russian Academy of Sciences, Professor Popov Str., 2,
St. Petersburg, 197376, Russia; potemkin_alexey@binran.ru
2 Polar-Alpine Botanical Garden-Institute, Kola Scientific Centre, Russian Academy
of Sciences, Kirovsk, Murmansk Province, 184256, Russia 3 Tsitsin Main Botanical Garden, Russian Academy of Sciences, Botanicheskaya Str., 4, Moscow, 127276, Russia; yur-mamontov@yandex.ru 4 Lomonosov Moscow State University, Leninskiye Gory, 1, Moscow, 119991, Russia;
bg_natagamova@mail.ru
Abstract. Study of selected specimens of Gymnomitrion collected by D. G. Long in Yunnan, China, revealed a new species, G. fissum Mamontov et Potemkin, sp. nov., with a fissured leaf surface. Comparison of SEM images of the leaf surface and leaf cross sections shows that the leaf surface of G. fissum is different from that of other known species with a superficially similar leaf surface, i. e. Mylia taylorii, M. verrucosa s. l. and Trabacellula tumidula. It has fissures around the cell lumen rather than grids and perforations. Outer cell walls of Gymnomitrion fissum are much thicker than in Mylia taylorii, M. verrucosa s. l. and Trabacellula tumidula, and their outer layers tend to be partly or completely caducous. G. fissum is related to the group of species assigned to the former genus Apomarsupella.
Keywords: cuticle, Gymnomitrion fissum, leaf surface, Yunnan, China.
Gymnomitrion fissum (Gymnomitriaceae, Marchantiophyta) — новый вид с трещиноватой поверхностью листа из Китая
А. Д. Потемкин1, Ю. С. Мамонтов1,2,3, Н. С. Гамова4
1 Ботанический институт им. В. Л. Комарова РАН, ул. Профессора Попова, д. 2, Санкт-Петербург, 197376, Россия; potemkin_alexey@binran.ru 2 Полярно-альпийский ботанический сад-институт им. Н. А. Авторина КНЦ
РАН, Кировск-6, Мурманская обл., 184256, Россия 3 Главный ботанический сад им. Н. В. Цицина РАН, Ботаническая ул., д. 4, Москва, 127276, Россия; yur-mamontov@yandex.ru 4 Московский государственный университет им. М. В. Ломоносова, Ленинские горы, 1, Москва, 119991, Россия; bg_natagamova@mail.ru
Резюме. В ходе изучения материалов по роду Gymnomitrion из провинции Юньнань, Китай, выявлен новый для науки вид Gymnomitrion fissum Mamontov et Potemkin, sp. nov. с трещиноватой поверхностью листа, напоминающей таковую других известных видов со сходной структурой поверхности листа — Mylia taylorii, M. verrucosa s. l. и Trabacellula tumidula. Сравнение снимков, полученных при помощи сканирующего и светового микроскопов, свидетельствует об
отличии этих видов по структуре поверхности листа и характеру утолщений наружных клеточных стенок. У Gymnimitrion fissum образуются трещины вокруг клеточных полостей, а не гребни и перфорации. Кроме того, наружные клеточные стенки у него значительно толще и их наружный слой частично или полностью отпадает. G. fissum близко родствен группе видов, ранее относившихся к роду Apomarsupella.
Ключевые слова: Gymnomitrion fissum, кутикула, поверхность листа, Юньнань, Китай.
Study of selected specimens of Gymnomitrion Corda collected by D. G. Long in Yunnan, China, revealed a new species with a fissured leaf surface (cuticle). The fissured leaf surface is exceedingly rare in liverworts. It is known in species of the genus Mylia Gray, sect. Mylia, and in the genus Trabacellula Fulford (Engel, Braggins, 2007).
Methods. We follow Buch (1928) in approach to measure complicate leaves of Scapania and define length of leaves from the middle of the insertion to the level of lobe tips. In terms we follow to Malcolm and Malcolm (2006). The photomicrographs were obtained with two microscopes equipped with digital cameras, a Leitz Wetzlar Orthoplan light microscope and an Olympus SZX16 dissection microscope. In order to better illustrate the three-dimensional objects, photomicrographs were combined from several optical sections using the software package HeliconFocus and some of the images were reconstructed in line drawings. SEM images were done using Scanning Electron Microscope JEOL JSM-6390LA.
Gymnomitrion fissum Mamontov et Potemkin, sp. nov. — Fig.; Plates I: 1a, 2-9, II: 1, 2, 9, 10, 14, 15, 17, 21-23, III, VI.
Diagnosis. Brownish plants with mature leaves having a ± fissured leaf surface and often deeper pigmented and narrowly recurved margins. Leaves equally bilobed, oval to subrotund, sheathing at the base, with a ± open sinus 0.3-0.4 the leaf length and leaf lobes chiefly obtuse. The species is further characterized by the stem with bleached smooth cortical layer and 2-3 brown intracortical layers.
Description. Plants in herbarium yellowish brown, with leaf margins often deep brown or rarely purple, erect; shoots 1.5-3.5 cm long and 0.7-1.9 mm wide, often with ventro-lateral (Fig.: 3; Plate I: 4), rarely with dorso-lateral (Andrewsianthus-type) intercalary branches with smaller leaves (Fig.: 3; Plate I: 6). Rhizoids not seen. Stem in cross section 11-13 cells thick, smooth, with ± bleached often smaller and thick-walled outer cortical cells and 2 layers of thick-walled, ± larger brown intracortical cell. Leaves bilobed, ± transversely inserted, sheathing stem at the base, with line of insertion arcuate, decurrent on dorsal and ventral side, ± conduplicate, usually with weakly arcuate longitudinal fold,
Fig. Gymnomitrion fissum Mamontov et Potemkin, sp. nov. 1, 2, 4 — sterile plants (1, 4 — two parts of the same shoot); 3 — part of a female plant with dorso-lateral and ventro-lateral intercalary branches. Scale bars: 1, 4 — 3 mm; 2 — 4 mm; 3 — 2 mm. All from Long 34684 (DUKE, holotype).
remote to contiguous and loosely imbricate not rare even on one shoot, ± broadly oval to rounded, x 0.85-1.2 as long as wide, ca. 600-750 цш long and 500-825 цш wide, with maximal width near the middle or a little below, the margins and sinus of the larger leaves often (but not always) very narrowly reflexed and remarkably deep brown. Sinus ± open, Y-, V- or U-like, 0.3-0.4(0.55) the leaf length. Lobes ± subequal, obtuse to obtusely pointed or nearly rounded. Leaf margins plane or recurved, almost smooth, ± papillose or ± notched due to uneven thickenings of marginal cell wall. Cells of leaves variable in size within a particular leaf sector, in lobes ca. 10-20 x 10-20 цш; marginal cells with evenly thickened and thin walls with distinct trigones, in 1(2) rows smaller than intramar-ginal cells, ca. 10-15 x 10-17 цш, adjacent to each other cells may differ in size, orientation and pattern of wall thickening; median cells 13-20(23) x 12-16 цш with large often bulging trigones and ± thickened to thin walls; median basal cells with smaller angular thickenings and ± thickened walls, 12-23 x 25-50 цш. Leaf surface varies from nearly smooth and finely punctate usually on smaller leaves to distinctly fissured, i. e., with flat papillae resembling cracked glass, locally somewhat obscuring areolation in larger leaves; such a structure of leaf surface is unevenly distributed throughout the leaf surface and sporadically distinct along leaf margin making it finely notched. In cross sections the leaf surface looks papillose or smooth whereas outer cell walls usually strongly thickened.
Dioecious. Female bracts somewhat larger than sterile leaves. Otherwise unknown.
Typ e. China, Fugong county, Lumadeng Xiang, Yapin Cun, E slope of Gaoligong Shan (Nu Jiang catchment), Burma/Yunnan border ridge, around lake south of «Yapin Pass», 27°12'21.3"N, 98°41'52.2"E. Alpine valley floor with lake, marshy ground and streams; in cushions on wet ground on lake shore. Alt. 3500 m. 12 August 2005 D. G. Long 34684, DUKE (Holotype)!
Etymology. The specific epithet refers to the fissured leaf surface of mature leaves.
Distribution and ecology: China, Yunnan, Burma/Yunnan border ridge. Alpine belt, 3500 m alt., on wet marshy ground on lake shore, in cushions.
Recognition and infrageneric position. The species somewhat resembles Gymnomitrion commutatum (Plates I: 1b, II: 3-8, 11-13, 16, 18-20, 24, 25) from which it differs in the larger size of plants of yellowish or lighter brownish color, sheathing at the base leaves with a deeper sinus, 0.3-0.4(0.55) the leaf length, and usually weakly arcuate folded, the fissured structure of leaf surface and locally notched leaf margins
of larger leaves, the stem with bleached cortex of often smaller thick-walled cells and brown intracortical cells. These two species also differ in branching mode. G. fissum has both ventro-lateral and dorso-lateral intercalary branches sometimes occurring on the same shoot (Fig.: 3; Plate I: 6), a feature which is characteristic for Apomarsupella (Schuster, 2002), whereas only ventro-lateral intercalary branches have hitherto been known for G. commutatum. Moreover, the ecological preferences of G. fissum according to the type specimen are also different from that of G. commutatum, which is a mesophyte, growing on soil in rock crevices and snow fields in Greenland (Schuster, 1988), Europe (Dierssen, 2001), South Siberia (Konstantinova et al, 2009; Mamontov et al., 2011; Afo-nina et al., 2012; ) and Russian Far East (Bakalin, 2008, 2009; Bakalin et al., 2009).
The phylogenetic position of G. fissum (as G. commutatum D. G. Long 34684, DUKE) was investigated by Shaw et al. (2015) from one nuclear (rpb2), two mitochondrial (nad1 and rps3), and seven plastid (atpB, psbA, psbT-H, rbcL, rps4, trnG and trnL) loci. In this study it was listed as G. commutatum based on a specimen from Yunnan (Long 34684, DUKE), which we now treat as the holotype of G. fissum. It was shown that G. fissum is related to the group of species earlier assigned to the genus Apomarsupella (R. M. Schust.) R. M. Schust.
Comparison with the other species with superficially similar leaf surfaces
The structure of leaf surface of Gymnomitrion fissum is a very rare among liverworts. G. fissum is the fourth known to us species with fissured leaf surface areolation when observed in a light microscope (LM). Despite the LM study of the leaf surface of G. fissum demonstrates its similarity with that of Mylia taylorii (Hook.) Gray, M. verrucosa Lindb. s. l. and Trabacellula tumidula Fulford, the SEM observations of leaf surface of these species exhibit their differences (cf.: Plates I: 3, 5, 6; II: 8; Engel, Braggins, 2005: Figs 1-3, 6, 7). Gymnomitrion fissum has fissures around the cell lumen (Plate VI: 3, 6) rather than grids and perforations of Mylia taylorii, M. verrucosa and Trabacellula tumidula. Moreover, a comparison of leaf cross sections of Gymnomitrion fissum, Mylia taylorii, M. verrucosa and Trabacellula tumidula demonstrates their considerable difference in outer cell wall thickness. Outer cell walls in G. fissum are much thicker than in Mylia taylorii, M. verrucosa and Trabacellula tumidula. The outer layers of cell walls in G. fissum tend to be partly caducous as it was shown by our SEM study (Plate VI: 4). The caducous outer walls in G. fissum probably predetermine the uneven distribution of
fissures throughout the leaf surface observed in a light microscope (Plates IV: 3, 5-7,10; V: 2).
Acknowledgements
The anonymous reviewers are thanked for careful reading of the manuscript, corrections and advices. We are grateful to Blanka Shaw (DUKE) for arranging loan of specimens of Gymnomitrion species. Help of Mrs. Lyudmila A. Kartseva in SEM study is gratefully appreciated. The study of authors Potemkin and Mamontov was carried out within the framework of the institutional research project 01201255616 of the Komarov Botanical Institute of the Russian Academy of Sciences. The study was supported in part by the Russian Foundation for Basic Research (research project nos. 15-04-03479, 16-04-01156). The research was done using equipment of The Core Facility Center «Cell and Molecular Technologies in Plant Science» at the Komarov Botanical Institute RAS (St. Petersburg, Russia).
References
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Plate I. Gymnomitrion fissum Mamontov et Potemkin, sp. nov. (1a, 2-9) and
G. commutatum (Limpr.) Schiffn. (1b). 1-9 — sterile plants, showing ventro-lateral (4) and both ventro-lateral and dorsolateral intercalary (6) branches. Scale bars: 1, 2, 4-6 — 2 mm; 3, 7-9 — 1 mm. 1a, 2-9 from Long 34684 (DUKE, holotype), 1b from Szweykowski s. n. (LE, Hepatoteca Polonica,
Fasc. VI, No. 139).
Plate II. Gymnomitrion fissum Mamontov et Potemkin, sp. nov. (1, 2, 9,10,14, 15, 17, 21-23) and G. commutatum (Limpr.) Schiffn. (3-8, 11-13, 16, 18-20.
24, 25).
1-4, 6, 8-10, 12-25 — sterile leaves; 5, 7, 11 — upper gynoecial leaves. Scale bar: 1 mm. 1, 2, 9,10,14,15, 17, 21-23 from Long 34684 (DUKE, holotype), 3-8,11-13, 16,18-20,24,25 from Szweykowski s. n. (LE, Hepatoteca Polonica, Fasc. VI, No. 139).
Plate III. Gymnomitrion fissum Mamontov et Potemkin, sp. nov. 1 — stem cross section; 2 — cells of leaf base; 3-5 — leaves; 6, 8, 9 — shoot sector, antical aspect; 7 — shoot sector, lateral aspect. Scale bars: 1, 2 — 100 pm; 3-5 — 500 pm; 6, 9 — 2 mm; 7 — 1 mm; 8 — 1.5 mm. All from Long 34684 (DUKE, holo-
type).
Plate IV. Gymnomitrion fissum Mamontov et Potemkin, sp. nov. 1,2, 4 — apices of leaf lobes; 3, 8 — cells of leaf margins; 5,9,10 — median leaf cells; 6, 7 — leaf cross sections. Scale bars: 1, 4, 5, 8, 9 — 25 pm; 2, 3, 6, 7, 10 — 50 pm. All from Long 34684 (DUKE, holotype).
Plate V. Gymnomitrion fissum Mamontov et Potemkin, sp. nov. 1, 3, 5 — leaves; 2 — apex of leaf lobe; 4 — median leaf cells. Scale bars: 1, 3, 5 — 500 pm; 2, 4 — 50 p.m. All from Long 34684 (DUKE, holotype).
Plate VI. Gymnomitrion fissum Mamontov et Potemkin, sp. nov. 1, 2 — leaves, outer surface; 3, 6 — median leaf cells, outer surface; 4 — cells of leaf base, outer surface; 5 — marginal leaf cells, outer surface; 7 — leaf, inner surface. Scale bars: 1, 2, 7 — 250 pm; 3 — 10 pm; 4 — 100 pm; 5 — 40 pm; 6 — 20 pm. All from Long 34684 (DUKE, holotype).
