蘚苔類研究（Bryol. Res.） 12（1）: 1‒5, July 2019

The gemma of pinnata （, ）

Tian-Xiong Zheng and Masaki Shimamura

Laboratory of and Ecology, Graduate School of Integrated Sciences for Life, Hiroshima University, 1‒3‒1 Kagamiyama, Higashihiroshima-shi, Hiroshima 739‒8526, Japan

Abstract. The novel morphology of gemma in Marchantia pinnata Steph., an endemic species to east Asia, is reported for the first time. The outer shape of gemma is gourd-like with maximum width ca. 250 µm and length ca. 350 µm. The surface is not smooth due to the swelling of the cells. The margin of gemmae is never entire due to mammillose and with several papillae on marginal cells. The two apical notches have no mucilage hairs. These morphologies are widely different from those of a com- mon species, M. polymorpha subsp. ruderalis with larger and nearly circular in outer shape, entire margin and mucilage hairs in notches. Morphological characters of gemmae might be useful for the identification of Marchantia species.

Key words: Marchantiaceae, Marchantia pinnata, gemma, mucilage hair

鄭天雄・嶋村正樹：ヒトデゼニゴケの無性芽（〒739‒8526 広島県東広島市鏡山1‒3‒1 広島大学大学院 統合生命科学研究科 植物分類・生態学研究室）

東アジア固有種であるヒトデゼニゴケ Marchantia pinnata Steph. の無性芽の形態について報告する． ヒトデゼニゴケの無性芽は，ひょうたん型の外形を持ち，長さと幅の最大値はそれぞれ350 µm，250 µm 程度，二つのノッチには粘液毛がない．また，無性芽の縁の細胞は円錐状のマミラを持ち，パピラが散 在する．これらの形態は，ほぼ円形でより大きな外形を持ち，縁が全縁，ノッチに粘液毛を有するゼニ ゴケの無性芽とは明らかに異なる．ゼニゴケ属における無性芽の形態の多様性は，種を識別するための 有用な形質として扱えるかもしれない．

gemmae is multicellular discoid structure with two Introduction laterally placed apical notches. The central part is several cells thick and becomes gradually thinner to- The propagule, organ gem- ward the unistratose margin（Shimamura 2016）. mae shows the high morphological diversity for each Marchantia pinnana Steph., an endemic species of taxon of liverworts. In leafy liverworts, unicellular or East Asia, was firstly described by Stephani and few-celled gemmae on the margins of the leaves or published by Bonner （1953） in later. The species the summit of the stem are typically observed. Fur- was a taxonomically enigmatic for a long time due to thermore, discoid multicellular gemmae arising on incomplete morphological description based on the the margins or the surfaces of the leaves are ob- mixture of two different species in type specimens. served in some epiphytic species（Cavers 1903）. In In the original description, although the morphology complex thalloid liverworts, many species produce of thallus was given correctly, the archegoniophore gemmae in cup-shaped structure called “gemma was misdesignated to that of M. emarginata subsp. cup” （or “cupules”）. In the Marchantia, the tosana. In Japan, the plant corresponding to M. pinnata

―1― 蘚苔類研究（Bryol. Res.） 12（1）, July 2019 have been called erroneously M. cuneiloba for a long time（Horikawa 1939, Hattori 1952, Mizutani 1984）. Materials and Methods The taxonomic confusion lasted until the lectotypifi- cation of M. pinnata by Bischler（1987） with exclu- In the Oct 20th of 2018, thalli bearing gemma cup sion of M. emarginata subsp. tosana. Since there was of M. pinnata were collected from a natural popula- such a taxonomic problem, morphological description tion in Kirishima-shi, Kagoshima-ken, Japan（Fig. 1）. on M. pinnata is still insufficient.（Bischer 1989）. M. pinnata is identified based on black line on the In this study, the detail morphology of gemmae in central thallus and the pinnatified appendages of ven- M. pinnata is firstly described. Through the compari- tral scales. M. polymorpha subsp. ruderalis was col- son with that of M. polymorpha subsp. ruderalis, we lected from Higashi-Hiroshima campus of Hiroshima propose that the morphology of gemmae may be a University, Hiroshima-ken, Japan. 10 or more num- decisive taxonomic character to distinguish the spe- ber of mature gemmae without stalk were picked cies. out from 10 gemma cups with forceps and it were observed under microscope.

Result

The mature gemmae of M. pinnata and M. poly- morpha exhibited similar morphologies, such as the multicellular discoid bodies with two notches and a trace of stalk. However, they differ in outer shape and size（Fig. 2）. The gemmae of M. pinnata（Fig. 2A） were long gourd-like shaped with 100‒250 µm in width（the distance between the two notches） and 150‒350 µm in height（the farthest distance between the trace of stalk and the margin of gemma）. The maximum size was ca. 250 µm in width and ca. 350 µm in width. On the other hand, the gemmae of

Fig. 1. Thalli of Marchantia pinnata bearing gem- M. polymorpha are larger and nearly circular in out- ma cups. er shape, with 200‒500 µm in width and 220‒650 µm

Fig. 2. Comparison of outer shape of gemmae in M. pinnata（A） and M. polymorpha subsp. ruderalis（B）. Ar- rowheads and asterisks indicate the two notches and a trace of stalk of each gemma respectively.

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Fig. 3. Transverse sections of gemmae in M. pinnata（A） and M. polymorpha subsp. ruderalis（B）. Arrow- heads indicate the cellular protrusions.

Fig. 4. Marginal cells of gemmae in M. pinnata（A） and M. polymorpha subsp. ruderalis（B）. Arrows indicate small papillae on the conically mammillose cells.

in height（Fig. 2B）. In transverse section, the gem- gion including marginal region with single-cell lay- mae of both species exhibited biconvex shape, thin- ered. In M. pinnata, the number of oil cell was ning out from the middle with multicellular layer to- smaller and restricted to the central region with ward to margin with single-cell layered（Fig. 3）. In multicellular thickness. In M. pinnata, the two apical M. pinnata, there were some indentations on the sur- notches are shallow and have no mucilage hairs（Fig. face due to the cellular protrusions（Fig. 3A）. On the 5A）. In M. polymorpha, the notches are more deep other hand, the surface of gemma was flat and and apical cells in the bottom of each notch were smooth in M. polymorpha（Fig. 3B）. The margin of covered with several mucilage hairs（Fig. 5B）. gemmae is never entire due to conically mammillose marginal cells with several papillae on marginal cells Discussion （Fig. 4A）. It contrasts with that of M. polymorpha with smooth margin（Fig. 4B）. In M. polymorpha, id- In general, the morphology of gemmae are very ioblastic oil cells sporadically distributed whole re- uniform throughout the genus Marchantia and it

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Fig. 5. Notches of gemmae in M. pinnata（A） and M. polymorpha subsp. ruderalis（B）. An arrow indicates the apical notch covered with mucilage hairs.

does not helpful to identify the species（Evans 1917, genus might provide surely species identification ap- Bischler 1993）. The morphological diversity of gem- proaches based on vegetative thallus. mae in the genus Marchantia has not received corre- sponding attention, despite physiological and develop- Specimens examined: M. pinnata Steph., Japan, mental research has been conducted in a common Kyushu, Kagoshima-Ken, Kirishima-Shi, Makizono- species, M. polymorpha（Mirbel 1835, Equihua 1987, Cho, Shimonakatsugawa, 100 m alt. on moist boulder Bowman 2016）. In this study, the morphological de- by roadside. October 20, 2018. Zheng 2（HIRO）; M. scription of gemmae in M. pinnata has been given polymorpha L. subsp. ruderalis Bischl. & Boissel.- firstly. It indicated that there is considerable mor- Dub., Japan, Honshu, Hiroshima-Ken, Higashihiroshi- phological diversity of gemma within the genus. Mor- ma-Shi, Kagamiyama, 230 m alt. on soil in open site. phological characters of gemma in M. pinnata, such November 1, 2018. Zheng 6（HIRO）. as gourd-like shape, smaller size, mamillose and pap- illose on the surface and no mucilage hairs in notch- Literature cited es were clearly different from that of M. polymorpha. Bischler, H. （1987）. The typification and synonymy of The gourd-like shape and smaller size of gemma in Japanese Marchantias described by Stephani. Bryolo- M. pinnata are similar to that of juvenile gemmae of gist 90: 331‒336. M. polymorpha（see Shimamura 2016）. However, the Bischler-Causse, H. （1993）. Marchantia L. The Asiatic morphological differences shown here does not de- and Oceanic taxa. Bryophyt. Bibl. 38: 1‒179. Bonner, C. E. B.（1953）. An unpublished section of vol. 6 rived from the different developmental stages. Be- of Stephani’s Species Hepaticarum the genus March- cause even after the several weeks cultivation in ar- antia. Candollea 14: 101‒112. tificial condition, these characters are stable, as long Bowman J. L.（2016）. A brief history of Marchantia from as the gemmae remained internal of gemma cup Greece to genomics. Plant Cell Physiol. 57: 210‒229. Cavers, F.（1903）. On asexual reproduction and regener- （data not shown）. ation in Hepaticae. New Phytologist 2: 121‒133. In the genus Marchantia, the morphology of sexual Equihua, C.（1987）. Diseminatición de yemas en March- branches（archegoniophore and antheridiophore） are antia polymorpha L. Cryptogam. Bryol. Lichénol. 8: relatively species-specific and are useful to identify 199‒217. Evans, A.W.（1917）. The American species of Marchan- the species. However, the during vegetative tia. Trans. Conn. Acad. Arts Sci. 21: 201‒313. growth with no sexual branches are sometimes lack- Hattori, S. （1952）. Hepaticae of Shikoku and Kyushu, ing decisive morphological characters. Further com- Southern Japan（2）. J. Hattori. Bot. 8: 21‒46. prehensive researches on gemma morphology in the Horikawa, Y. （1939）. Bryophyta. In Asahina, Y. （ed.）

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Nippon Inkwasyokubutu Dukan, Sanseido, Tokyo. Mizutani, M. （1984）. Checklist of Japanese Hepaticae pp.783‒992.（in Japanese） and Anthocerotae. Proc. Bryol. Soc. Japan 3: 155‒163. Lu, Y-W. & S.-F. Huang,（2017）. Marchantia L.（March - （in Japanese） antiaceae-Marchantiophyta） in Taiwan. Taiwania 62: Shimamura, M.（2015）. : Taxono- 55‒62. my, phylogeny and morphology of a model system. Mirbel C. -F.（1835）. Researches anatomiques et physi- Plant Cell Physiol. 57: 230‒256. ologiques sur le Marchantia polymorpha, pour servir a l’histoire du tissu cellulaire, de l’épiderme et des sto- （Accepted: April, 1, 2019） mates, Mém. Acad. R. Soc. Inst. France 13: 337‒436.

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