全 文 ：山茶科濒危植物猪血木的花器官发生
?
张瑞菊1 , 2 , 马海英1 , 王跃华1
??
(1 云南大学生命科学学院 , 云南 昆明 650091; 2 山东菏泽学院学前教育系 , 山东 菏泽 274015)
摘要 : 利用扫描电镜首次观察了山茶科极濒危植物猪血木 ( Euryodendron excelsum) 的花器官发生过程。猪
血木的花为两性完全花 , 萼片和花瓣均为 2?5 螺旋向心发生 , 单轮排列 , 且有逆时针和顺时针两种方式。
雄蕊的形成是先形成一个环形分生组织 , 然后在环形分生组织上以 2?5 螺旋产生 5 束雄蕊原基 , 每一束雄
蕊原基的第一雄蕊原基都是在对萼的位置产生 , 其它的雄蕊原基在其两侧产生。3 心皮顺序发生 , 愈合成
3 室单子房 , 柱头平截不裂。猪血木与山茶亚科的花器官发生明显不同。
关键词 : 山茶科 ; 厚皮香亚科 ; 猪血木属 ; 花器官发生
中图分类号 : 944 文献标识码 : A 文章编号 : 0253 - 2700 (2007) 06 - 648 - 07
Early Floral Development of Endangered Euryodendron
excelsum (Ternstroemioideae : Theaceae)
ZHANG Rui-Ju1 , 2 , MA Hai-Ying1 , WANG Yue-Hua1 **
(1 Collegeof Life Sciences, Yunnan University, Kunming 650091 , China;
2 Collegeof Preschool , Heze University, Heze 274015 , China)
Abstract: Thefloral development of a critically endangered plant Euryodendron excelsumfromTernstroemioideae (Theace-
ae) has been observed under scanningelectronmicroscope (SEM) for the first time . The flower of E. excelsumis bisexual
and teleianthous . Fivesepal primordia are initiated2?5 spirally andarranged inone whorl whenmature, and so are petals .
Sepals and petals are initiated in the same order either clockwise or counterclockwise in the same flower . The androecial
part isa ringprimordiuminthe beginning . Thefirst five stamen primordia are initiatedonthis ringprimordiumat antisepal-
ous positions and then other stamen primordia appear on two sides of each of the first five primordia . Finally a total of 25
stamen primordia are initiated fromthe ring primordiumand arranged in one whorl but could be grouped into 5 fascicles .
Three sequentially initiated carpels compose an ovarywhich has an axile-central placenta with three locules and atruncate
and indehiscent stigma . The floral development of E. excelsumis distinctly different from plants in Theoideae .
Key words: Theaceae; Ternstroemioideae; Euryodendron; Floral ontogeny
Euryodendron excelsum is a monotypic generic
plant of Ternstroemioideae, Theaceae . The species is
endemic to China, only distributed in Guangdong Prov-
ince (Lin, 1998) . It is a critically endangered species
(Hilton-Taylor, 2000 ) , previously only more than 80
living plants found in wild (Wang et al . 2002) . Mor-
phologically E. excelsum is between Eurya and Cley-
era . Its phylliformand phyllotaxy aresimilar to Eurya,
while its flower structure is similar to Cleyera ( Chang,
1963) . Thus the species is very important for under-
standing the relationships the genera in Ternstroemi-
oideae . As it is an endangered species, study on it will
also serve for its conservation biology .
Ternstroemioideae is traditionally a subfamily of
云 南 植 物 研 究 2007 , 29 (6) : 648～654
Acta Botanica Yunnanica

?
?? ?Author for correspondence; E-mail : wangyh58212@ 126 . com
Received date: 2006 - 12 - 25 , Accepted date: 2007 - 09 - 13
作者简介 : 张瑞菊 (1968 - ) 女 , 山东菏泽 , 硕士 , E-mail : shangqian—0 @163 . com ?
Foundation item: This work is funded by the National Science Foundation of China (Grant No . 30560017 ) .
Theaceae, although it was established as a separate
family Ternstroemiaceae in early nineteenth century .
The circumscriptionof family Theaceaehasbeengreatly
modifiedover thepast 100 years . Cronquist (1981) in-
cluded four subfamilies in Theaceae: Theoideae, Tern-
stroemioideae, Bonnetioideae and Asteropeioideae .
Dahlgren ( 1983 ) excludes Bonnetioideae, and Airy-
Shaw (1936) , Hutchinson ( 1969 ) , Rouleau ( 1981 ) ,
Goldberg ( 1986 ) , Thorne ( 1992 ) and Takhtajan
(1997 ) only recognize Theoideae ( or Camellioideae)
and Ternstroemioideae . So most modern plant systems
accept Theoideae ( or Camellioideae) and Ternstroemi-
oideae as coregroups of Theaceae .
Recent molecular studies, nevertheless, provided
new evidences and indicated different phylogenetic re-
lationships in Theaceae . Most studies found Theoideae
and Ternstroemioideae to each bemonophyletic but not
sister to each other (Morton et al , 1996 , 1997 a, b ;
APG, 1998; Savolainen et al . 2000; Soltis et al .
2000; Anderberg et al . 2002 ) , and APG (1998) fur-
ther suggested two distinct families Theaceae and Ter-
stroemiaceae . But in later studies using more samples
themonophyly of Ternstroemioideaewas only moderate-
ly supported (Prince and Parks, 2001) or not support-
ed by mitochondrial matR sequences ( Yang et al .
2006) . Therefore the recognitionof two distinct famili-
es should be accepted with caution, and the relation-
ships between Theoideae and Ternstroemioideae still
need further studies . For various reasons, Theoideae
received more attention while Ternstroemioideae was
studied much less from all respects . Few studies from
Ternstroemioideaemake it difficult to analyze the evo-
lutionary relationships in Theaceae, so the study on
taxaof Ternstroemioideae is urgently in need .
In the last decades, floral development has come
to be indispensable for an integrated study of any high-
er rank taxon ( Endress, 1994; Tucker, 1996 ) . In
Theaceae, studies on floral ontogeny of most genera in
Thoideae were studied by different authors ( Erber,
1986; Sugiyama, 1991; Tsou, 1998 ) , but there has
been no report on Ternstroemioideae . The objective of
this study is to investigate the floral ontonegy of E. -
excelsum, therefore to provide evidence for systematic
relationships of Euryodendron with other taxa and for
further study of Ternstroemioideae .
Materials and Methods
Plant materials of E. excelsumwere collected in June 1998
from Bajia, Yangchun County, Guangdong Province . Flowers of
all stages were fixed in formalin-acetic acid-alcohol (FAA , for-
malin∶acetic acid∶70 % ethanol = 1∶1∶18 ) . Voucher specimens
(He Han & Wang Yue-Hua, 998001 ) were deposited at the
Herbariumof Yunnan University . Materialsweregenerally exam-
ined and carefully dissected under a dissecting microscope in
95% ethanol , and dehydratedthrough an ethanol-isoamyl acetate
series, and dried with a Hitachi HCP-2 critical point dryer .
Samples were then mounted on stubs and Au?Pt sputter coated
with SPI-Module Sputter Coater . Prepared samples were exam-
ined with Hitachi S-800 Scanning Electron Microscope (SEM)
and recorded on Shanghai Panchromatic film .
Results
Initiation of floral primordium and bract
Every year new leaves sprout from late March to
earlyApril , although E. excelsum is an evergreen tree .
Floral buds are subtended by small vegetative leaveson
new branches or by bud scales on perennial branches .
The floral primordia are hemispherical in shape ( Plate
Ⅰ : 1) . With the development of floral primodia, the
first bractlet primordium ( Plate Ⅰ : 2) gradually dif-
ferentiates fromthe sideof the apex . Then another ap-
pears in theopposite position and is covered by the first
one . The two bracts are same sized in mature flowers .
Filiformhair gradually appears with the development of
bracts, so the bracts are finally hairy (PlateⅠ : 3) .
Perianthial initiation
There are 5 sepals and 5 petals in E . excelsum,
but in the beginning the 10 perianth primordia are ho-
mogeneous in appearance and they differentiate into se-
pals or petalsonly at late floral development .The peri-
anth primordia are initiated quincuncially and their
bases are basically triangular . The sequence of initia-
tionof the sepals and petals is spiral throughout, fol-
lowing a2?5 phyllotactic pattern either clockwise ( Plate
Ⅰ : 3 , 5 , 6) or counterclockwise (PlateⅠ : 4 ) , but
in same sequence in one flower . Each primordium is
round-domed in the beginning . With the continual ac-
tivity of the meristem, these primordia elongate and
heighten graduallywith more expansion in lateral direc-
tions . During this progress, the primordia differentiat-
ed: the first initiated five developed into small , stout,
and brownish sepals; thelatter fivebecame large, flat-
tened, and white-yellowish petals . The calyx and co-
rolla are distinct, and the five sepals are arranged in
onewhorl , as are the five petals ( Plate Ⅰ : 6 , Plate
9466 期 ZHANG Rui-Ju et al .: Early Floral Development of Endangered Euryodendron excelsum . . .
Ⅱ : 16) , although the members of each whorl is via
spiral initiation . So the basis of each whorl is quin-
quangular ( Plate Ⅱ : 16) in fully developed flowers .
Androecium initiation
After the fifth petal is initiated, the floral apex
looks like a flattened pentagon ( Plate Ⅱ : 7 ) , then
becomes saucer-like when the androecium is about to
originate ( Plate Ⅱ : 8 ) . When the gynoecial part be-
gins to appear, the androecial part is a ring-like pri-
mordium . The initiation of stamen primordia is not si-
multaneously evenly sized . The first five stamen pri-
mordia are initiated antisepalously in a2?5 spiral on the
ring-likeprimordium (PlateⅡ : 10 - 15) , and thespi-
ral direction is same as that of the sepals . Then the
other stamen primordia appear at two sides of each pri-
mordium . And again theother primordia areinitiated at
two sides of these previous three primordia, so that a
total of four stamen primordia appear around each of
first five primordia and finally a total of 25 stamen pri-
mordia exist in every flower . During the process of an-
droeciuminitiation, as the previously initiated primor-
dia are bigger than the later ones (Plate Ⅱ : 12 , 13 ,
15) , every five primordiamake up a fascicle, with the
first one as the center (PlateⅡ : 12) . With thedevel-
opment of the later primordia, the size differences
among the primordia become smaller and smaller and
finally all stamens are same in size and arranged inone
whorl ( Plate Ⅱ : 13) .
All stamen primordia are hemispherical at begin-
ning, then turn ellipsoidal before eventually become
column-like in shape ( Plate Ⅱ : 15 - 18) and they are
same sized as the differentiation of sepals and petals
finished . Shortly, with the middle of the stamen pri-
mordia broadening, the primordia begin to differentiate
(Plate Ⅱ : 19) , from which the upper triangular part
will become anther and the lower columnar part will be-
come filament ( Plate Ⅱ : 20 ) . The edges of mature
anther will be covered with hairs (Plate Ⅱ : 20 ) . Fi-
nally, atotal of 20 - 25 stamens, with the lengthof 1 .5
- 2 .0 mm, are arranged in one whorl .
Gynoecium initiation
The gynoecium of E. excelsum comprises three
carpels (Plate Ⅱ : 9 , 10 , 11 , 12 , 13 , 16 ) , but oc-
casionally two-carpellategynoecia (Plate Ⅱ : 14 , 15)
could be seen . The carpels are initiated separately
( Plate Ⅱ : 9 , 10 , 11 ) , within the above-described
central flattened base of the floral apex before stamen
primordia emerge . Carpel primordia appear as hemi-
spherical bulges in the beginning, and then expand
more in lateral directions . Later, the two lateral sides
of such a primordium involute and so that make the
carpellary chamber becomes more and more evident on
theventral side . When stamen primordia become fin-
ger-shaped, the fusion of carpels is basically complete
(Plate Ⅱ : 17 , 18) , and the gynoecium looks like a
ball .Then, with thedifferentiationof stamen primordia
and the development of anthers, a single and un-
branched stigma (PlateⅡ : 19) emerges and thegyno-
ecium become bottle-shaped . The fully developed flow-
ers all possess axile-central placentas with two or three
locules, and the ovary is evidently superior, with the
attachments of both androecium and gynoecium on the
flat surfaceof the receptacle . Thedevelopmentof a two
carpellary gynoeciumis similar to a three carpellary one
(PlateⅡ : 14 , 15) .
Discussion
Ternstroemioideae includes about 10 genera and 6
occur in China . No comparable work has been done to
other taxon in Ternstroemioideae, but majorities of
Theoideae, seven from total ten genera, were studied
by different authors ( Erber, 1986; Sugiyama, 1991;
Tsou, 1997 , 1998) . According to Tsou (1998) , early
floral development in Theoideae shows diversity in sev-
eral aspects and could be grouped into two groups ac-
cording to these differences: in some taxa the perianth
primordia only differentiate into sepals and petals at
late development and this is called group I , while in
group II the calyx and corolla aredistinct at inception .
Moreover, group II can be divided into twosubgroups,
in group IIa individual stamens are initiated from five
fascicle primordia and the placentation is axile-basal ,
whereas in Group IIb, no androecial fascicles are
formed and the placentation is axile-central . In each
group the floral development is very similar and thedif-
ference in each group is minor . Tsou (1998) conclud-
ed that the two groups represent two evolutionary lin-
eages . Group I is the earlier evolved lineage and Group
II is the later derived lineage . However, the differenc-
es of floral development only exist in the early stage of
development . With the development goes on, the dif-
ferences become small and the mature flowers in
Theoideae are all similar in appearance: they all have
sepals and petals, and they all have numerous sta-
056 云 南 植 物 研 究 29 卷
mens .
Compared with Theoideae, the floral organogene-
sis of Euryodendron excelsum has some distinct fea-
tures: it has only one whorl of stamens and the initia-
tion pattern of stamen primordia is rather special . That
there isonlyonewhorl of stamens in E. excelsum is not
newly found in this study, as it can be seen by naked
eyes, and this has traditionally been one of the differ-
ences between Theoideae and Ternstroemioideae ( Cron-
quist, 1981; Dahlgren, 1983; Hutchinson, 1969;
Thorne, 1992; Takhtajan, 1997 ) . This distinction
may be considered only numerical and insignificant if
not this study . This study has indicated that this is not
only numerical but also substantial . In E . excelsum,
when the androecial part is about to originate, it is a
ring primordium . Then five stamen primordia appear at
antisepalous positions, that is, alternate with petals .
Following that, atotal of four stamenprimordiaare ini-
tiated on two sides of eachof these first five stamens in
a laterally centrifugal sequence, and thus every five
primordia, thevery first one and the later four, forma
fascicle . In Theoideae, the ring primordia at thebegin-
ning of androeciuminitiation only occur in group I but
the following development is not like that of E . exc-
elsum . In this group, fromthe ring primordium, about
10 - 13 stamen primordia appear along the footline to
formthe first whorl , and then the second and the fol-
lowing whorls are initiated in a centrifugal sequence
(Tsou, 1998) . During this process, stamen primordia
of each whorl are not initiated synchronously, but they
are definitely not initiated in the special sequence as
that of E. excelsum . In group IIa and group IIb of
Theoideae, no ringprimordiumbut five fascicleprimor-
dia or androecial zone appear before stamen primordia
initiation ( Tsou, 1998 ) . The fascicle primordium in
group IIa is a bulge in formand a pro-primordia struc-
ture, and the stamen primordia on each fascicle are
initiated nearly simultaneously (Tsou, 1998 ) . So the
fascicle primordia in this group, though used same
word“fascicle”, is astructurebefore individual stamen
appear and different from the concept of our current
study . Ingroup IIbof Theoideae, stamenprimordia are
initiated from five androecial zones ( Tsou, 1998 ) .
Five stamen primordia appear first on the lowermost
marginof each zone, and each initiation zone expands
upward and outward continuously, followed immediate-
ly by the inception of the stamens of higher orders
(Tsou, 1998) . Thus the primordia initiation in group
IIb is also different fromthat of E . excelsum . The floral
developmental characters of Theoideae and Euryoden-
dron are summarized in table 1 .
As the only representative of Ternstroemioideae,
E. excelsum in this study shows very different early flo-
ral development . It is hard to conjure this floral devel-
opment type has some connection with or has derived
from any typeof Theoideae . Sofromthe present study,
we could conclude that E . excelsumis not closely relat-
ed with Theoideae . Therefore this result also support
that Ternstroemioideae is only distantly related with
Theoideae . Though usingonegenus to represent Terns-
troemioideae seems not solid, this result has been sup-
ported by other studies . Embryological studiesonmem-
bers of Ternstroemioideae, e.g . Yang and Min′s
(1995a) work on Pyrenaria and Tutcheria and Tsou′s
(1995) study on Adinandra, Cleyera and Eurya also
indicated that the embryological characters of Ternstro-
emioideae are very different from those of Theoideae,
suggesting they are two distinct groups .
Table 1 Comparison of the floral development of Theoideae and Euryodendron
Taxa Perianth Androecium Gynoecium
Theoideae
group Ⅰ
11 ?-16 perianth primordia initiated in a spiral
sequence . Theyoung perianthmembers areho-
mogeneous at inception, only differentiated in
later stage .
Numerous stamens initiated individually and
centrifugally on the whole androecial region .
Stamens numerous, 2 R-5 whorled .
2 J, 3 or 5 carples,
axile-central placenta
Theoideae
group Ⅱa
Theoideae
group Ⅱb
Sepal primordia and petal primordia are distinct
at inception . Thefive sepals and the fivepetals
are arranged in two whorls .
Individual stamen primordia initiated from five
fascicle primordia centrifugally . Stamens nu-
merous, > 5 Hwhorled .
Individual stamen primordia initiated from five
peripheralslopes centrifugally . Stamens numer-
ous, 2-3 whorled .
5 Jcarples, axile-basal
placenta
3 or 5 carples, axile-
central placenta
Euryodendron
Sepal primordia and petal primordia are distinct
at inception . Thefive sepals and the fivepetals
are imbricate .
Individual stamen primordia initiated fromring-
likeprimordia . Every fiveprimordia formafas-
cicle . Stamens 25 ?, 1 whorled .
2 Jor 3 carples, axile-
central placenta
1566 期 ZHANG Rui-Ju et al .: Early Floral Development of Endangered Euryodendron excelsum . . .
Some other studies also have been conducted on
members of Theoideae and Ternstroemiaceae . Theflow-
ers of Ternstroemioideae members are less diverse than
Theoideae members . Studies on pollen morphology
(Dickison, 1982; Wei , 1997; Xu et al . 2005) and
work on Leaf epidermis (Zhang and Zhuang, 2004) all
indicated that membersof Theoideae havegreater diver-
sity than members of Ternstroemiaceae in these re-
spects . Molecular works, on the contrary, have proved
themonophyly of Theoideae whilemonophyly of Terns-
troemiaceae was not supported (Yang et al . 2006 ) . In
Prince and Park′s ( 2001 ) phylogenetic study on
Theaceae s. l ., 7 species from5 generaof Ternstroemi-
oideae were sampled, but E. excelsumwas not includ-
ed . In their study, Theoideae ( Theaceae s.s .) as a
monophyletic group was strongly supportedwhileTerns-
troemioideae was only moderately supported, and this
two clades were not sister to each other . Yang et al .
( 2006 ) conducted another phylogenetic study on
Theaceae using mtDNA matR sequence and 6 species
representing 6 genera in Ternstroemioideae were sam-
pled, inwhich E. excelsumwas included . But in their
study, 6 taxa fromTernstroemioideaedid not even form
one clade while Theoideae was strongly supported as a
monophyletic group . This has led us to reconsider the
relationships among taxa of subfamily Ternstroemi-
oideae .
The present study provided new evidence of dis-
crepancies between Ternstroemioideae and Theoideae .
However, aswehave addressed above, the relationship
of themis complicated . Further studies on more mem-
bers are urgently needed to clarify the relationships
amonggroups in Ternstroemioideae .
Acknowledgements : We thank Mr . Fan Xi-Kai from Kunming
Institute of Botany, Chinese Academy of Sciences for his help in
using the Scanning Electron Microscope and taking photos .
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Explanations of Plates
Plate Ⅰ : 1 - 6 . Floral development of E. excelsum . 1 . the hemispheri-
cal floral primodium has grown away from the bud scales; 2 . The floral
meristem has bifurcated, leaving a lateral branch complex meristem adja-
cent to the first bract ( B1) and the floral meristem ( F ) adjacent to the
second bract; 3 . The initiation of two bracts with some long hair, and
successive initiation of the first three sepal primordia in a clockwiseorder
at the apex of the flower; 4 . Top view of thebud, showing thefive sepals
and first two petals initiated in a counterclockwise order; 5 - 6 . Top views
of the young flower, showing initiation and the shape of sepals and two
petals primodia in a clockwiseorder , pleasenote that sepalsand petals are
initiated in the same order in the same flower .
Plate Ⅱ : 7 - 20 . Floral development of E . excelsum . 7 . Top view of the
floral apex from 6 , two sepals are removed and the other three existed .
Showing the apex is pentagonal and flat; 8 . Top view of the floral apex af-
ter 7 , showing the concave floral apex; 9 . Floral apex showing initiation
of the three carpel primordia, in different sizes, and the ring- like androe-
cial primordium around the carpels; 10 - 11 . Top view of the floral apex,
three carpels just slightly fused at the base, and the earliest stamens just
initiated on the ring- like androecial primordia; 12 . Lateral view of 13 ,
some stamens appear clearer and their development is not synchronous;
13 . Top view of 12 , three carpels fused deeply, five stamens are clearly
bigger than others; 14 . Two carpels are initiated in different sizes, and
someof the earliest stamensare just initiated; 15 . Two carpels fused after
14 , and five stamens are bigger than others as in 12 and 13; 16 . Floral
bud with sepals and petals removed, showing five sepals and five petals
arranged in two whorls although they are initiated in a spiral , and both
have aquinquangular base; 17 - 18 . With the development of the floral
bud, all stamens reach the same size; 19 . Three carpels fuse completely
and form a truncate style; partial stamens begin to differentiate; 20 . All
stamens differentiated into anther and filament gradually, and some long
hair grows on the stamens with the development of the flower .
张瑞菊等 : 图版Ⅰ ZHANG Rui-Ju et al : Plate Ⅰ
3566 期 ZHANG Rui-Ju et al .: Early Floral Development of Endangered Euryodendron excelsum . . .
张瑞菊等 : 图版Ⅱ ZHANG Rui-Ju et al : Plate Ⅱ
456 云 南 植 物 研 究 29 卷