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New Observations on the Morphology and Structure of Marchantia polymorpha Gametophores in Sexual Reproduction Adaption

地钱生殖托形态结构新观察及其对有性生殖的适应



全 文 :植物科学学报  2013ꎬ 31(6): 555~561
Plant Science Journal
    DOI:10􀆰 3724 / SP􀆰 J􀆰 1142􀆰 2013􀆰 60555
地钱生殖托形态结构新观察及其对有性生殖的适应
曹建国ꎬ 王全喜ꎬ 邹红梅ꎬ 戴锡玲ꎬ 曹 同
(上海师范大学生命与环境科学学院ꎬ 上海 200234 )
摘  要: 用显微观察技术对苔类植物地钱(Marchantia polymorpha)生殖托的形态结构进行了研究ꎬ 本研究的新
观察包括: (1)生殖托具有明显的背腹分化ꎬ 被认为是叶状体为适应有性生殖而高度特化的直立枝ꎻ (2) 雌托盘
的 9~11个指状裂瓣中边缘两个稍不同ꎬ 除了两个边缘裂瓣外的其他裂瓣间具雌苞ꎮ 托柄具有背腹之分ꎬ 雌托
柄背面具光合组织ꎬ 并向两侧扩展形成纵沟ꎬ 雌托柄的腹面具 2条被鳞片重叠覆盖相互平行的纵沟ꎬ 内具假根ꎻ
(3)与雌托柄不同ꎬ 雄托柄外观平滑ꎬ 背面无光合组织及纵沟ꎮ 观察发现ꎬ 伞状的雌托能滞留水分ꎬ 并沿雌托柄
的纵沟缓慢释放连续的水流ꎬ 游动精子沿着纵沟内的水流到达雌托下面的颈卵器ꎮ 上述观察表明地钱生殖托的
结构是对有性生殖的一种适应ꎬ 这有助于我们理解地钱受精作用的机理ꎮ
关键词: 地钱ꎻ 生殖托ꎻ 雄托ꎻ 雌托
中图分类号: Q945          文献标识码: A          文章编号: 2095 ̄0837(2013)06 ̄0555 ̄07
      收稿日期: 2013 ̄05 ̄03ꎬ 修回日期: 2013 ̄09 ̄12ꎮ
  基金项目: 上海市教委重点项目(12ZZ128)ꎻ 上海市科委项目(12490502700)ꎮ
  作者简介: 曹建国(1968 ̄)ꎬ 男ꎬ 博士ꎬ 教授ꎬ 主要从事植物生殖发育与资源植物研究(E ̄mail: cao101@shnu􀆰 edu􀆰 cn)ꎮ
New Observations on the Morphology and Structure of Marchantia
polymorpha Gametophores in Sexual Reproduction Adaption
CAO Jian ̄Guoꎬ WANG Quan ̄Xiꎬ ZOU Hong ̄Meiꎬ DAI Xi ̄Lingꎬ CAO Tong
(College of Life and Environment Sciencesꎬ Shanghai Normal Universityꎬ Shanghai 200234ꎬ China )
Abstract: The morphology and structure of the gametophores of the liverwort Marchantia
polymorpha were studied using light microscopy􀆰 New observations included: ( 1 ) The
gametophores had distinct dorso ̄ventral differentiation and were highly specialized upright
branches of the thallus bearing sex organs􀆰 (2) Two marginal ones of 9-11 rays of the female
receptacle were distinguished by their slightly different sizes compared with others􀆰 There was
no involucre between the two marginal ones􀆰 The dorsal region of the archegoniophore stalk
was comprised of photosynthetic tissueꎬ which extended laterally and formed two narrow
grooves under the extended photosynthetic tissue􀆰 The ventral region of the stalk consisted of
two ̄parallel rhizoid furrows half ̄wrapped by overlapping scales􀆰 (3) In contrast to the female
archegoniophoreꎬ the antheridiophore stalk was smooth and no photosynthetic tissue or
grooves were formed in the dorsal region􀆰 The umbrella ̄shaped female receptacle retained
waterꎬ which could be released slowly along the grooves to form a tiny water flowꎬ through
which the spermatozoids swam to the archegonia􀆰 The morphology and structure of the Marchantia
receptacles were adaptations to sexual reproductionꎬ and can help us to understand the
mechanism of fertilization in Marchantia.
Key words: Marchantia polymorphaꎻ Gametophoreꎻ Antheridiophoreꎻ Archegoniophore
The gametophytes of Marchantia polymor ̄
pha L􀆰 exhibit dorso ̄ventral differentiation and are
dioecious􀆰 The female plant produces archego ̄
niophores ( female receptacles ) and the male
plant produces antheridiophores (male recepta ̄
cles) at maturity􀆰 Major events of Marchantia
sexual reproduction such as the development of
sexual organs and embryos and the formation of
sporophytes have been studied previously[1-4] 􀆰
Ultrastructural aspects of spermatogenesis and
oogenesis in Marchantia polymorpha have also
been investigated[5-8] . Although sexual reproduc ̄
tion in Marchantia has been researched for more
than a centuryꎬ some questions remain unre ̄
solved􀆰 For exampleꎬ how do sperm cells reach
the female receptacle atop the elongated stalk􀆰
The present investigation revealed that the trans ̄
port of sperm may be related to the structure of
the stalk and female receptacle􀆰 The morphology
and structure of Marchantia polymorpha gameto ̄
phores are reported here in detailꎻ these obser ̄
vations can help to understand the mechanism of
sexual reproduction in this species.
1  Materials and Methods
Living Marchantia polymorpha L􀆰 plants
were collected from the botanical garden of the
Shanghai Normal University􀆰 Gametophytes with
male or female gametophores were cultured in a
pot covered with plastic film on a shaded north ̄
facing balcony􀆰 Young to mature gametophores
were observed with a Nikon SMZ ̄1500 stereo ̄
microscope and photographed for morphological
investigation􀆰 For the structural (anatomical) in ̄
vestigationꎬ the gametophores and stalks were
cut and fixed with 3% glutaraldehyde in 0􀆰 1 mol / L
phosphate buffer at room temperature for 6-12 h􀆰
The specimens were subsequently washed three
times with the same buffer and fixed in osmic
acid (2% aqueous solution) for 2 h and washed
again with the same buffer three times􀆰 After de ̄
hydration in a graded acetone seriesꎬ the speci ̄
mens were infiltrated with a mixture of acetone
and Spurr􀆳s resin (SPI ̄Chemꎬ USA)ꎬ and then
embedded in pure resin􀆰 Specimens were thick
sectioned with glass knives􀆰 The sections were
stained with Toluidine blueꎬ observed and photo ̄
graphed using a Nikon E ̄800 microscope.
2  Results
2􀆰 1  Archegoniophore
Archegoniophores are highly specialized re ̄
productive organs with distinct dorso ̄ventral
structure􀆰 The archegoniophore stalk is more or
less square ̄shaped in appearance􀆰 A dorsal re ̄
gionꎬ two lateral regions and a ventral region
was distinguished clearly ( Fig􀆰 1: aꎬ fꎬ iꎬ jꎻ
Fig􀆰 2: a) . The dorsal region facing towards the
thallus was equivalent to the upper surface of the
horizontal thallus􀆰 The ventral region facing away
from the thallus was equivalent to the lower sur ̄
face of the thallus ( Fig􀆰 1: aꎻ Fig􀆰 2: a) . The
umbrella ̄shaped female receptacle consisted of
9-11 raysꎬ which were distinguished into two
marginal rays and 7-9 normal rays (Fig􀆰 1: bꎬ
cꎻ Fig􀆰 2: b) . The two marginal rays faced to ̄
wards the dorsal region of the stalkꎬ and no invo ̄
lucre was produced between the two marginal
rays (Fig􀆰 1: bꎬ cꎻ Fig􀆰 2: b) . In contrastꎬ in ̄
volucres were produced between each of the
adjacent pairs of normal rays other than the two
marginal rays (Fig􀆰 1: bꎬ cꎻ Fig􀆰 2: b) . Dissec ̄
tion of the mature receptacle showed that each
involucre contained 3-4 pocket ̄shaped pseudo ̄
perianths (Fig􀆰 1: d) . Each pseudoperianth con ̄
tained a sporophyte protected by an archegonial
jacket ( calyptra) when youngꎬ but the sporo ̄
phyte extended out of the calyptra due to the
elongation of the sporophyte stalk at maturity
(Fig􀆰 1: eꎬ Fig􀆰 2: c) . Henceꎬ the sporophyte
was protected by the calyptraꎬ pseudoperianth
and involucre during maturation (Fig􀆰 2: c) . Al ̄
though a group of archegonia arose in each invo ̄
lucreꎬ only 2-3 sporophytes grew up.
655 植 物 科 学 学 报 第 31卷 
ArP
St
DR
4 mm
2 mm 2 mm
1 mm 1 mm 40 mμ
200 mμ
10 mm100 mμ
1
m
m
1
m
m
NR
IN
NR
NR
MR
NR NR
MRIN
St DR
IN
PP
SP
PP
IN
IN
C
AP
Gr
AP
AC
R
VRD
R
DR AR
ACGr
Gr
RF
VR
Sc
R
RF
b
a
c
gfed
h
i
k
lj
0.
5
m
m
a􀆰 Archegoniophore (ArP) with a long stalk (St) . Dorsal region (DR) of the stalk facing towards the thallusꎻ b􀆰 Apical view of female
receptacle showing two marginal rays (MR)ꎬ normal rays (NR)ꎬ and involucres ( IN)ꎻ c􀆰 Ventral view of archegoniophoreꎬ showing no
involucre produced between the two margin rays􀆰 Upper surface of stalk (St) in dorsal region (DR)ꎻ d􀆰 Involucre ( IN) openingꎬ and
pseudoperianth (PP) seen insideꎻ e􀆰 Dissection of involucre ( IN)ꎬ showing pseudoperianth (PP)ꎬ calyptra (C)ꎬ and sporophytes
(SP)ꎻ f􀆰 Dorsal region of stalkꎬ showing green photosynthetic tissueꎻ g􀆰 Air pore (AP) on upper epidermis of dorsal regionꎻ h􀆰 Lateral
side of stalkꎬ showing groove (Gr) . Ink (arrow) flowed along the grooveꎻ i􀆰 Ventral region of stalkꎬ showing two rhizoid furrows (RF)ꎻ
j􀆰 Transverse section of stalkꎬ showing air chambers (AC)ꎬ air pore (AP)ꎬ and groove (Gr) in dorsal region (DR)ꎻ rhizoid furrows
(RF)ꎬ scales (Sc)ꎬ rhizoids (R) in ventral region (VR)ꎻ k􀆰 Longitudinal section of stalk through dorsal region (DR) and ventral region
(VR)ꎻ l􀆰 Umbrella ̄shaped archegoniophore retaining large drop of water.
Fig􀆰 1  Archegoniophore of Marchantia polymorpha
755  第 6期                    曹建国等: 地钱生殖托形态结构新观察及其对有性生殖的适应(英文)
The dorsal region of the stalk was composed
of photosynthetic tissue ( Fig􀆰 1: f) . Air pores
were seen in the upper epidermis of the dorsal
region ( Fig􀆰 1: g) . Transverse and longitudinal
sections showed that the chambers and photo ̄
synthetic filament cells were formed inside􀆰 Each
chamber possessed an air pore in the central
part of the upper epidermis (Fig􀆰 1: jꎬ k) . The
side view of the stalk and transverse section
showed that the photosynthetic tissue extended
laterally and formed a narrow groove under the
extended tissue (Fig􀆰 1: hꎬ j) . Some multicellu ̄
lar hairs arose in the groove (Fig􀆰 1: j) . Adding
black ink to the base of a stalk in a sloping posi ̄
tion showed that the ink flowed upwards along
the groove ( Fig􀆰 1: hꎬ arrow ) . In the ventral
region of the archegoniophore stalkꎬ two rhizoid
furrows were clearly recognized ( Fig􀆰 1: i) . A
transverse section of the stalk showed that the
rhizoid furrow was not enclosedꎬ but half ̄wrapped
by overlapping scales (Fig􀆰 1: j) . The longitudi ̄
nal section showed a distinct dorso ̄ventral differ ̄
entiation of the stalk (Fig􀆰 1: k) . The rays of the
female receptacle were also dorso ̄ventrally differ ̄
entiated􀆰 Each ray was formed by a half enclosed
thallus􀆰 The seam in the lower surface of the ray
could be clearly seen (Fig􀆰 1: cꎻ Fig􀆰 2: b).
2􀆰 2  Antheridiophore
The antheridiophore had a reddish elongated
stalk and no distinct dorso ̄ventral appearance
(Fig􀆰 3: a) . Magnified observations showed that
the dorsal region possessed no green photosyn ̄
thetic tissue or air chamber differentiation (Fig􀆰 3:
bꎬ d). In the ventral region of the antheridiophore
stalkꎬ two rhizoid furrows could be clearly recog ̄
nized by their light color (Fig􀆰 3: c) . The trans ̄
verse section of the stalk showed that the rhizoid
furrow was not yet enclosedꎬ but wrapped by
overlapping scalesꎬ and many rhizoids could be
seen within it ( Fig􀆰 3: dꎬ e) . The disk ̄shaped
AC
AP
RC
R
Ar
RF
R
VRDR
AP
AC
StRay
R
Sc
NR
IN
MR
C
PP
SP
IN
a c
b
a􀆰 Archegoniophore with a long stalk (St)ꎬ showing air chambers (AC)ꎬ air pore (AP) in upper surface of the receptacle and dorsal
region (DR) of the stalkꎻ archegonia (Ar) at the base between the rays􀆰 Rhizoid furrow (RF) and rhizoids (R) in the stalk and raysꎬ
Scꎬ scaleꎻ b􀆰 Ventral view of the female receptacle showing the margin rays (MR)ꎬ normal rays (NR) and involucres ( IN)ꎻ c􀆰 Involucre
( IN)ꎬ containing pseudoperianth (PP)ꎬ calyptra (C)ꎬ and sporophyte (SP) .
Fig􀆰 2  Schematic diagram of archegoniophore
855 植 物 科 学 学 报 第 31卷 
male receptacle usually consisted of 6 -8 lobes
that resembled flower petals in appearance
(Fig􀆰 3: f) . The slightly depressed upper surface
of the male receptacle could hold rain waterꎬ which
was favorable for sperm release (Fig􀆰 3: g) . The
male receptacle consisted of many chambersꎬ
each of which contained an antheridium (Fig􀆰 3:
h) . The matured antheridia released the sperm
cells through the cap cell and the sperm travelled
of the antheridial chamber through the channel
(Fig􀆰 3: hꎬ arrow) .
2􀆰 3  Observations on the fertilization process
To see whether the sperm could swim to the
female receptacle up the elongated stalkꎬ an un ̄
fertilized female receptacle was selected􀆰 (We
chose a female plant with an archegoniophoreꎬ
but with no male plants nearby) . Water was then
sprayed on the female plant to simulate rain􀆰 As
a resultꎬ a large water drop was suspended un ̄
der the female receptacle ( Fig􀆰 1: l ) . At the
same timeꎬ we added a drop of water on the up ̄
per surface of the male receptacle (Fig􀆰 3: g) . If
AnP
St
DR
RF
VR
DR
RF RF
R
RF
Sc
AC
An
5 mm 10 mm 100 mμ
5 mm 100 mμ 50 mμ
2 mm 2 mm
hgf
eVR da
cb
a􀆰 Antheridiophore (AnP) with a long stalk (St)ꎻ b􀆰 Dorsal region of stalkꎻ c􀆰 Ventral region of stalkꎬ showing two rhizoid furrows (RF)ꎻ
d􀆰 Transverse section of stalkꎬ showing two rhizoid furrows (RF) in ventral region (VR)ꎻ e􀆰 Magnification of part of Fig􀆰 dꎬ showing rhi ̄
zoid furrow (RF)ꎬ scales (Sc) and rhizoids (R)ꎻ f􀆰 Apical view of male receptacleꎻ g􀆰 Slightly depressed upper surface of antheridio ̄
phore retaining water􀆰 h􀆰 Longitudinal section of antheridiophoreꎬ showing antheridia (An) in air chamber (AC)ꎻ Arrow indicates open ̄
ing of antheridium chamber.
Fig􀆰 3  Antheridiophore of Marchantia polymorpha
955  第 6期                    曹建国等: 地钱生殖托形态结构新观察及其对有性生殖的适应(英文)
there were mature antheridia in the male recepta ̄
cleꎬ sperm were rapidly released and formed a
slightly whitish sperm suspension􀆰 The sperm
suspension was absorbed with a pipette and
added onto the base of archegoniophore stalk􀆰
Ten minutes laterꎬ a drop of water just under the
female receptacle was absorbed with a new pi ̄
pette and checked for sperm cells under a micro ̄
scope􀆰 Results showed that the drop of water
contained spermꎬ and we deduced that sperm
can reach the female receptacle through continu ̄
ous tiny water flow in the groove of the stalk.
3  Discussion
Although many studies on the structure and
development of gametophyteꎬ sex organsꎬ em ̄
bryos and sporophytes have been conducted on
Marchantia species[1ꎬ7-15]ꎬ the morphology and
structure of the gametophores have not been de ̄
scribed in detail previously􀆰 We investigated the
morphology and structure of the female and male
receptacles and their stalksꎬ and helped to clari ̄
fy the mechanism of sexual reproduction in
Marchantia polymorpha.
3􀆰 1  Structure and function of the archegoniophore
The present investigation showed that the
archegoniophore was a specialized upright branch
of the thallus adapted for sexual reproduction􀆰
Although the stalk of the archegoniophore be ̄
came uprightꎬ it possessed obvious dorso ̄ven ̄
tral differentiation􀆰 The dorsal region of the stalkꎬ
with differentiation of photosynthetic tissueꎬ was
equivalent to the upper surface of the thallus􀆰
The ventral region of the gametophore stalkꎬ with
rhizoid furrowsꎬ was equivalent to the lower sur ̄
face of the thallus midrib􀆰 Haupt[12] also deter ̄
mined that the gametophores in Rebouliaꎬ As ̄
terella and Conocephalum represented specia ̄
lized upright branches of the thallus􀆰 Based on
the featuresꎬ we suggested that the female re ̄
ceptacle rays were a palmately branched system
of specialized thalli􀆰 The two marginal rays wereꎬ
in factꎬ marginal branches of the palmate thal ̄
lus􀆰 This explains why no female reproductive
organs were formed between the two marginal
rays􀆰 The heterogeneity of the rays in Marchantia
polymorpha was first described here􀆰 This inter ̄
pretation has important significance for under ̄
standing the function of the female gametangio ̄
phore.
Haupt[12] indicated that the female recepta ̄
cle in Marchantia reached its greatest degree of
specialization and that the archegonial receptacle
consisted of rays alternating with groups of
archegonia􀆰 Howeverꎬ the function of the spe ̄
cialized female receptacle was rarely mentioned
or discussed􀆰 The present investigation showed
that the umbrella ̄shaped receptacles had the
ability to accumulate water ( Fig􀆰 1: l)ꎬ which
flowed slowly downwards along the elongated stalk􀆰
Microscopic observation and ink ̄water experi ̄
mentation showed that the water flowed along the
grooves along the two sides of the stalk (Fig􀆰 1:
h) . It can be inferred that the specialized struc ̄
ture of the archegoniophore has an important
function in sexual reproduction􀆰 The continuous
tiny water flow provided a medium for sperm to
swim to the archegonia in the female receptacle.
3􀆰 2  Structure and function of the antheridiophore
The morphology and structure of the an ̄
theridiophores differed greatly from those of the
archegoniophores􀆰 The male receptacle pos ̄
sessed no raysꎬ but rather had 6 -8 shallower
lobes􀆰 It had a slightly depressed upper surfaceꎬ
which could hold a little water and was favorable
for sperm release􀆰 Although the male stalk was
dorso ̄ventrally differentiated like the female stalkꎬ
there was no distinct difference between the dor ̄
sal and ventral surfaces in appearance􀆰 The male
stalk had no green photosynthetic tissue in the dor ̄
sal region􀆰 In additionꎬ no groove was formed in
the male stalk􀆰 The structural features of the March ̄
antia antheridiophore were undoubtedly adapted for
the release and transport of sperm􀆰 As the sperm
065 植 物 科 学 学 报 第 31卷 
cells were releasedꎬ they dropped rapidly to the
soil and swam to the female receptacle.
3􀆰 3   Archegoniaꎬ sporophytes and the tissues
outside of them
Haupt[12] also determined that female recep ̄
tacles in Rebouliaꎬ Asterella and Conocephalum
were commonly hemispherical or conical and more
or less lobed􀆰 Each lobe represented a separate
growing point from which either one or several
archegonia arose􀆰 In Marchantiaꎬ the archego ̄
nial receptacle did not have lobesꎬ but instead
consisted of a number of rays􀆰 The present in ̄
vestigation showed that no archegonia were
formed between the two marginal rays􀆰 Numer ̄
ous multicellular hairs arose from between the two
marginal rays when the female receptacle was
young􀆰 The hairs undoubtedly enhanced the abi ̄
lity to retain waterꎬ which was advantageous for
sperm reaching the archegonia.
The present observations showed that sporo ̄
phyte development and involucre formation were
as described in previous work[12ꎬ16] 􀆰 The arche ̄
gonia were naked before fertilizationꎻ and only
paraphyses existed between archegonia􀆰 The
naked archegonia and paraphyses were favora ̄
ble for fertilization􀆰 After the egg was fertilizedꎬ
the archegonial jacket developed into the calyp ̄
traꎬ within which the embryo grows􀆰 Thenꎬ an
additional envelopeꎻ i􀆰 e􀆰 ꎬ the pseudoperianthꎬ
arose outside the fertilized archegonium􀆰 At the
same timeꎬ an involucre arose around the arche ̄
gonia􀆰 All these tissues served to protect the
young sporophyte.
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(责任编辑: 王豫鄂)
165  第 6期                    曹建国等: 地钱生殖托形态结构新观察及其对有性生殖的适应(英文)