Gametophyte and Embryo of Microgonium tahitense (Hymenophyllaceae)

8 Pages·1992·0.67 MB·English

by  Reiko Yoroi

植物研究雑誌
J. Jpn. Bot.
67: 169-176 (1992)
Gametophyte and Embryo of Microgonium tahitense
(Hymenophyllaceae)
Reiko YOROI
Seitoku University，53 1 Sagamidai，Ma tsudo，Ch iba，27 1 JAPAN
ゼ、ニゴケシダの配偶体と伍
鎧礼子
聖徳大学 271千葉県松戸市相模台 531
(Received on October 28，19 91)
Spores of Microgonium tahitense (Nadeaud) Tindale (Hymenophyllaceae)，co llected from Yonaguni
Is ，.1Ryukyu，w ere cultivated for three years. The spore germination showed aT richomanes-type by
Nayar and Kaur (1971)，an d Ip and Ir types by the author (1972). In the early development，pr othallial
cells took an irregular form due to the appearance of the first rhizoidal cel1. Gametophytes were
branched filaments and formed antheridia and archegonia on archegoniophores. Young sporelings，
which put on calyptras，w ere born by fertilization. Gemmae were formed actively on the filaments.
The first frond divided soon into lateral veins and false veins from the midrib. A sporangium
contained 64 spores and the count of gametic chromosome numbers was n=3 4. This plant collected
from Yo naguni Isl. w出 asexual diploidぉ confirmedby the observation of both gametophyte
and sporophyte.
Microgonium ltαhitense (Nadeaud) Tindale is a gametophyte，th e embryology in the sporophyte，
small，pe ltate，a nd epiphytic or saxifragous filmy and the chromosomal data.
fern growing on wet rocks in valleys and on the 恥1aterialsand恥1ethods:The fertile fronds of
barks of trees in forests in the Ryukyus，t he 凡licrogoniumtahitense were collected in October
Bonins，F ormosa，J av a to New Guinea，ea stwards 1974 and in M ch1991 by the author on Mt.
紅
to north-east Australia and Polynesia. Urabu，Y onaguni Is ，.1 Okinawa Pref. Voucher
Since Bower (1888)，s exual and apogamous specimens (Yoroi 5435 and 6182) are deposited in
growth in the Hymenophyllaceae has been the Herbarium of the University of Tokyo. The
described on several species by several workers. fertile fronds were washed with tap water，an d the
The embryological information in the family was sporangia were removed from them to keep in
very poor，i ncluding the recent works of Stone clean drag-papers，w here the spores were shed.
(1958) and Yoroi (1976)，a nd M. tahitense has They were preserved in ar efrigerator after being
never been observed in i臼 embryology. dried for several hours in the shade.
In this paper，an account will be given on this The spores were sown on am edium with in-
species as to the developmental morphology in the organic nutrient in Petri-dishes. The medium was
-169ー
170 植物研究雑誌第67巻第3号 平成4年6月
Meyer's solution solidified with 0.80/0 agar. The ト2).A prothallial cell usually arises from one of
dishes were placed in ac ulture box kept at 23 :t 1C the three corners directed to the former side-walls
0
under 12 hours of illumination ad ay with white (Fig. 1-3，4) . The development of the prothallial
fluorescent tubes at 300-1000 lux. Five months cell at the corner directed to the basal wall is much
later，t he young gametophytes were planted on less frequent.
sterilized soil in small flower pots kept in the When the prothallial cell develops into as hort
laboratory at 23-250C under the same light prothallial filament with two or more transverse
conditions. wall formations，t he second and the third pro-
Embryos were fixed with Craf 1( Sass 1958)， thallial cells begin to arise from the remaining
embedded in paraffin，s ectioned at 8μm by corners of the basal cell (Fig. 1-6，7 ，8) . The pro-
microtome，a nd stained with Delafield's hemato- thallial cells often produce lateral branches (Fig.
xylin. The fronds with sporangia were fixed in 15，8). The cells are small，c ompared with those
・
Newcomer's solution in the field for cytological of the other Trichomanoid ferns. They show
study. The gametic chromosome numbers were variously shaped barrel-forms and contain much
counted in the fronds with the acetocarmine squash less chloroplasts than the basal cell. Transforma-
methods of Manton (1950). Photographs and tion to the rhizoidal cell is recognized by the dis-
camera-lucida drawings were made on the micro- appearance of the chloroplasts included in the
tome sections of both gametophyte and sporo- distal cell of the prothallial filament.
phyte，in cluding those of gametic chromosomes. Within six months，a b ranched prothallium
Observations: Thes por回 aregreen，te trahedral- grows to as ize of about 1.5 mmin diameter (Fig.
globose in shape with three ridges of laesurae on 1-9). In about eleven months，t he profusely
the spore coatσig. 1-1). The exine is thin and branched prothallium seems roughly to be as phere
spiny. Usually，a s porangium contains 64 regular of about 5m m泊diameterwith radially emitting
spores. The average diameter of the spores is 29.0 filaments and rhizoidal cells in all directions. No
μm. longitudinal cell division occurs in the filaments
When the exnine splits at the laesurae as the until the formation of sex organs.
spore swells，a c ushion-like cell (basal cell) pro- In eighteen months' culture，th e formation of
trudes out of it. The cell is chlorophyllous and has antheridium occurs on由eprothallial filament. The
four corners directed to the three side-walls and antheridium arises from the filament cell as
加
one basal wall of the spore coat. The formation outgrowth，a s is shown in the formation of
of the basal cell takes pla∞within two weeks after antheridia of Polyphlebium venosum (R. BR.)
sowing. The fully swollen basal cell is two to three Copeland (Stone 1958). The outgrowth is rich in
times as large as the original spore，bu t it is smaller chloroplasts and produces a stalk cell and a
as compared with the other previously reported spherical cell. The spherical cell cuts off two ring
species of the family. cells，on e dome-shaped cell with an operculum and
About one month after sowing，th e basal cell one central cell. By as uccession of cell divisions
for the first time cuts off ar hizoidal cell，w hich the central cell produces numerous spermatozoids，
contains af ew pale chloroplasts. The rhizoidal cell which move out actively when the operculum is
is produced on an upper surface of the basal cell shed. During the cell divisions，th e stalk cell，th e
or some times at one corner of the basal cell (Fig. ring cells and the dome-shaped cell are filled with
June 1992 Journal of Japanese Botany Vol. 67 No. 3 171
1
@
bc
Fig. 1. Germination of spores and young gametophytes. 1. Spore. 2-4. One month after sowing. 2. First rhizoidal
cell protruding. 3. First prothallial cell protruding. 4. Basal cell protruding ap rothallial cell and ar hizoidal cell.
5-7. Two months. 5. Basal cell with ab ranched fiIament. 6-7. Basal cell with two filaments. 8. Three months. Basal
cell with three filaments. 9. Six months. Prothallium with branched filaments and rhizoidal cells. bc: basal cell，
sc: spore coat，rc : rhizoidal cell. Bar= 100μm.
chloroplasts，b ut these disappear at maturity. lateral filament near to the basal portion of the
Figure 21shows two mature antheridia. mother filament，an d sometimes midway on it. The
・
In a few weeks after the formation of archegoniophore is stalked and bears several
antheridium，a n apical cell is produced by the archegonia of various ages. Figure 2-2 shows a
repeated oblique wall-formations on the prothallial small archegoniophore protruding three old and
filament. The apical cell loses its activities soon， one young archegonia. Each archegonium bears an
resulting in the formation of am ass of cells like egg cell，a v entral canal cell，ne ck canal cells and
a sphere，a s is shown in the formation of the four neck cells in tiers of four to five cells. The
archegoniophores of Cnψidomanes bilabiatum (N. neck cells stand vertically，a s is seen in the
et Bl.) Copel. (Stokey 1948). The archegonio- Osmundaceae (Fig. 3-1).
phore is usually found at the distal end of the In about twenty months' culture，th e formation
172 植物研究雑誌第67巻第3号 平成4年6月
Fig. 2. Sex organs，y oung sporelings and ag emma. 1-2. 18 months after sowing. 1. Antheridia. 2.
Archegonia on an archegoniophore. 3-4. 20 months. 3. Early stage of as poreling，wi th ah air. 4.
Later stage of as poreling，wi th hairs. h: hair. 5. 21 months. Ag emma on ag emmifer. Bar= 100μm.
of ay oung sporeling occurs for the first time. Polyphlebium ven，o脱 m(Stone 1958). The embryo
Figure 2・3shows an external view of the young grows soon to ay oung sporeling，wh ich is accom-
sporeling of about 300μm in length，wh ich bears panied by several multicellular (between two and
ab icellular hair at the tip. Figures 32aandbs how four cells) hairs σig. 2-4). The calyptra is still
・
slightly oblique microtome cross sections of the observed in由ecross section of the young sporeling
younger embryo of 100μm in diameter. The (Fig. 33).Naturally，th e first frond is formed at
・
embryo is wrapped in ac alyptra，w hich has been the distal end of the sporeling，w hile the first
broken by this time，as is shown in the embryo of rhizoid of the frond comes from near the proximal
June 1992 Journal of Japanese Botany Vol. 67 No. 3 173
Fig. 3. Sections of archegoniophores and embryos，a nd first fronds. 1. Archegoniophore with three archgonia.
2. Two sections of an embryo with calyptra. 3. A section of as poreling with calyptra. c: calyptra. 4. 21 months
after sowing. First frond with am idrib and rhizoids. 5-6. Two years. 5. Early stage of the development of the first
frond. 6. Later stage.恥1idribdividing lateral veins and false veins，an d lower side of the frond protruding rhizoids.
r: rhizoid. Bars = 100 t.tm in the upper figures and bars = 1m mi n the lower figures.
portion (Fig. 3-4). The first frond makes up a cell，w hich takes a flask-like shape. Then the
midrib and am arginal meristem in the early stage terminal cell is cut off at the place of constriction，
of the development. As cells of the marginal giving rise to an initial cell of the gemma，le aving
meristem are active in the first frond，th e midrib the lower cell as ag emmifer. The initial cell is
begins to divide into lateral veins and false veins divided by transverse walls to form the gemma
σig. 3-5). Figure 3-6 shows af urther grown-up (Fig. 2-5). When both terminal cells of the gemma
stage of the first frond，f rom which arises a begin to form two rhizoidal primordia，th e gemma
number of rhizoids from the margin and the lower falls on the ground to grow an ew protha1lial fila-
surface of the proximal portion，as is shown re- ment. The formation of gemmae continues for one
cently in the sporophyte of this species by ye訂 tillthe gametophytes form am at，a nd then
Hagemann (1988). The root is not recognized at it ceases. The shape of gemmae is regular，as is
all. shown in that of Gonocormus minutus (Bl.) v. d.
After one year and nine months from the Bosch. (Yoroi 1972).
beginning of the culture，th e vegetative reproduc 百legametic chromosome number of n= 3 4 has
幽
tion is accomplished by ag emma，as is shown in been confirmed for this species σig. 4). In this
the formation of gemma of Gonocormus minutus species the size of chromosomes is very small，co m-
(Bl.) v. d. Bosch. (Yoroi 1972). The gemma paring with that of the other Trichomanoid ferns.
appears at the distal end of the prothal1ial filament Discussion: The type of spore germination in
and is as hort on~ composed mostly of eight to nine this species corresponds to“Trichomanes type"
cells. The gemma develops first from at erminal according to Nayar and Kaur (1971)，an d to“Type
174 植物研究雑誌第67巻第3号 平成4年6月
Fig. 4. Gametic chromosomes. n= 34. Bar = 10μm.
Ip" and “Ir" of the author (1972). NCl ribbonlike Bierhorst 1975). In Microgonium tahitense，t he
且
plates ediscovered in this species，th ough the young sporophyte has developed from an egg cell
訂
gametophyte is of the snetype as usual in the in the archegonium，wh ich forms ac alyptra after
担
other Trichomanoid ferns (Farrar and Wagner fertilization. In this species，as ;f asthe author
紅
1968，Yo roi 1985). If the appearance of rhizoidal has observed，an apogamous embryo takes place
cells is suppressed on the basal cell，la ter develop- neither on the archegoniophore nor on the arche-
ment of the prothallial filaments is directed in gonial jacket cell，as is shown in Vandenboschiα
，
straight lines，ke eping the angle of 1200 regularly αuriculatlα(Stokey 1948)，in Trichomαnes [s. lat.]
between them. Such ac ase is usual恒Gonocormus pinnαtum (Bierhorst 1975) and in Crψidomanes
，
minutus (B1.) v. d. Bosch. and Crepidomanes latemαrginale (Eaton) Copel. (Yoroi 1976).
insigne (v. d. Bosch.) Fu. (Yoroi 1972). However， Since Bower (1888) described gemmae，t he
the usual case for this species is that the rhizoidal vegetative reproduction of the gametophytes has
cell develops in an earlier stage，an d the prothallial been known in the Hymenophyllaceae. The repro-
filaments take an irregular disposition. The duction has been also observed in the Vittariaceae
irregularity aforesaid is also observed in Vanden- (Farrar 1974，Y oroi 1975，S heffield and Farrar
boschia radicans (Sw.) Cope1. var. orientale (C. 1988) and in the Grammitidaceae (Stokey and
Chr.) H. Ito， V. auriculatα(B1.) Cope ，.1 Atkinson 1958). Although the development of
Selenodesmium obscurum (Bl.) Copel. and S. gemmae usually takes place in parallel with that
siamense (Christ) Ching et Wang (Yoroi 1972， of mother gametophytes，it has begun after the
1985). The irregularity and regularity in the earlier formation of sex organs in this species. The
development seems to depend mainly on the gametophytes have resulted加amat condition by
specific nature of spores in those species，n ot- continuous gemma-formations. These facts might
withstanding influence from the culture's be adapted to the environment of extremely moist
condition. air or of wet conditions，in which血isspecies lives.
The formation of sex organs on the The chromosome number of n= 3 4 found in
gametophytes has been commonly observed in the plants from Yo naguni Is1. agrees with the count
Hymenophyllaceae (Mettenius 1864，Bo wer 1888， by Braithwaite (1975). He also reported the count
Goebe11892，St okey 1948，Ho lloway 1944，St one of n=3 4 for M. motleyi v. d. Bosch and that of
1958，F arrar and Wagner 1968，Y oroi 1972， n= 6 8 for M. bimarginatum v. d. Bosch (Braith-
June 1992 Journal of Japanese Botany Vol. 67 No. 3 175
waite 1969，19 75). As for chromosome numbers， (Forst.) Presl. Trans. Roy. Soc. N. Z. 74: 196-206.
Manton 1. 1950. Problems of cytology and evolution in
plants in this genus have either 34 or am ultiple
the Pteridophyta. Camb ridge Un iversity Press，
of this number. Cambridge.
Mettenius G. 1864. Uber die Hymenophyllaceae. Abhand .l
Considering the developmental morphology of
d. K. S. Geselsch. d. Wissensch. 11: 403-504.
both gametophytes and sporophytes，th e average Nayar B. K. and Kaur S. 1971. Gametophytes of homo-
sporous ferns. Bot. Rev. 37: 295-396.
number of spores in the sporangium，a nd the
Sass J. E. 1958. Botanical microtechnique (3rd ed.).
chromosome numbers of this genus，t he plant lowa State Univ. Press，A mes.
collected by the author is considered to be as exua1 Sheffield E.加 dFarrar D. R. 1988. Cryo sem examination
of g emma formation in Vittaria grαminifolia. Amer.
diploid. J. Bot. 75: 894-899.
St okey A. G. 1948. Reproductive structures of the gameto
田
phytes of的lmenophyllumand Trichomanes. Bot. Gaz.
The author express her sincere thanks to Prof. 109: 363-380.
一一一一一andAtkinson L. R. 1958. The gametophyte of
Emer. Takasi Tuyama of Ochanomizu University
the Grammitidaceae. Phytomorphology 8: 391-403.
fo r his kindness shown to her through this study Stone 1. G. 1958. The gametophyte and embryo of
and cultivation. The author is also grateful to Prof. Polyphlebium venosum (R. Br.) Copeland (Hymeno・
phyllaceae). Aust. J. Bot. 6: 183-203.
Emer. Hirosi Itoo f Tokyo Kyoiku University for Yoroi R. 1972. Studies on spore germination and gameto-
phyte of Japanese Hymenophyllaceae. Sci. Rep. Tokyo
his continuous encouragement. The author is also
Kyoiku Daigaku (B) 15: 81-110.
indebted to Prof. Paul Reasoner，P h. D. of 一一一一1975. Spore germination and gametophyte
development of the Vittariaceae (1). J. Jpn. Bot. 50:
Seitoku University for his reading the manuscript.
33-43.
一一一一1976.Gametophyte and apogamous embryo of
Crepidomanes latemarginαle from Isl. Ishigaki，Ry ukyu.
References
J. Jpn. Bot. 51: 257-267.
一一一一一一1985.Observations of two species of Selenodes-
Bierhorst D. W. 1975. The apogamous life cycle of
mium from Isl. Iriomote，R 抑止yu.Kenkyukiyo Seitoku
Trichomanes pinnatum - a confirmation of
U凶v.18: 99-107 (in Japanese).
Klekowski's presentations on homosporous pairing.
Amer. J. Bot. 62: 448-456.
Bower F. O. 1888. Primary note on the formation of
gemmae on Trichomanes alatum. Ann. Bot. 1: 要旨
183-184.
一一一一1888.On some normal and abnormal develop- 小笠原，琉球列島から台湾，ジャワを経て，ニュー
ments of the oophyte in Trichomanes. Ann. Bot. 1: ギ、ニア，オーストラリア東部からポリネシアにま
269-305.
Braithwaite A. F. 1969. The cytology of some Hymeno- で広く分布するゼ、ニゴケシダの配偶体と腔発生を
phyllaceae from the Solomon Islands. Br. Fern Gaz. 胞子(与那国島で採集)からの培養実験 (3年)
10: 81-91.
一一一1975.Cytotaxonomic observations on some によって観察した.胞子の発芽様式は Nayarと
Hymenophyllaceae from the New Hebrides，Fi ji and Kaurの類型では Trichomanes-typeを，著者
New Caledonia. Bot. J. Linn. Soc. 71: 167-189. (1972)の分類ではIp型と Ir型を示すが，初生仮
Farrar D. R. 1974. Gemmiferous fern gametophytes -
Vittariaceae. Amer. J. Bot. 61: 146-155. 根の発生が早いため，その後の発達は不規則にな
一一一一一andWagner W. H. Jr. 1968. The gametophyte of りがちである.前葉体は糸状体で，造精器と造卵
Trichomanes holopterum Kunze. Bot. Gaz. 129:
器の両生殖器官が発達すると，若い胞子体が生じ
210-219.
Goebel K. 1892. Archegoniatenstudien uber die Gesch- る.腔発生の初期にはカリプトラが観察されるこ
lechtesgeneration der Hymenophyllaceae. Flora 76:
とから，この腔は有性生殖によって生じたと考え
92-116.
Hagemann W. 1988. Microgonium tahitense (Nadeaud) る.生殖器官の発達後に無性芽による増殖が盛ん
Tindale (Hymenophyllaceae)，e in Farn mit peltaten になり，前葉体はマット状になる.とりわけ小形
Blattern. Beitr. Biol. Pflanzen 63: 115-137.
な前葉体が環境のなかで生きるのにこのことは適
Holloway J. E. 1944. The gametophyte，e mbryo and
developing sporophyte of Cardiomanes reniforme している.第一葉では展開の早い時期に中肪から
176 植物研究雑誌第67巻第3号 平成4年6月
側脈や偽脈を分化し，胞子葉に顕著に見られる仮 配偶体と胞子体の観察結果から，与那国島のゼニ
根の発生も観察された.大きさの揃った胞子は 1 ゴケシダは2倍体の有性生殖種であると認めた.
胞子嚢あたり64個で染色体数はn=34であった.