全 文 ：武汉植物学研究 2004，22(5)：469～472
Journal o|Wuhan Botanical Research
乐昌含笑(木兰科)的核型研究
王恒昌，何子灿，李建强 ，孟爱平，蔡清
(中国科学院武汉植物园，武汉 430074)
摘 要：首次报道了乐昌含笑(Michelia chapensis)的染色体数目和核型。核型公式为 2 =38=28 m+6 sm+4 St
(2SAT)。与前人认为整个含笑属都为单一的 2A型不同，乐昌含笑的核型属于 Stebbins的 2B型，具有 2对近端着
丝粒染色体。而且发现在第 9对染色体上有小随体的存在。这些表明在含笑属内含有不同的核型。乐昌含笑在细
胞学意义上可能是属内比较进化的类群。对染色体结构的细微改变在木兰科植物的种属进化上的作用进行了简要
讨论。
关键词 ：木兰科；含笑属；乐昌含笑；核型研究
中图分类号 ：Q942 文献标识码：A 文章编号：1000—470X(2004)05—0469—04
Karyotypical Studies on Michelia chapensis Dandy(Magnoliaceae)
W ANG Heng—Chang，HE Zi—Can，LI Jian—Qiang’，MENG Ai—Ping，CAI Qing
(Wuhan Botanical Garden，The Chinese Academy of Sciences，Wuhan 430074，China)
Abstract：Michelia chapensis Dandy is firstly karyomorphologically studied．Its karyotype can be
formulated as 2n一38—28 m +6 sm+ 4 st(2SAT)，belonging to Stebbins’S 2B type．This iS a
new karyotype report，which，different from the previous confirmation that in Michelia group，
the whole karyotypes of genus are of uniform 2A and there iS no st chromosome occurred．There
might be different karyotypes within Michelia，and M．chapensis is probably a relatively advanced
species．We briefly discuss the role of minor chromosomal structural alterations played in evolu—
tion of genus or species in Magnoliaceae．
Key words：Magnoliaceae；Michelia；M ．chapensis；Karyotype．
Michelia L．consists of about sixty taxa．M．
chapensis Dandy iS one of the famous ornamental
timber plants in Magnoliaceae[ ．It has a relatively
broad distribution in Jiangxi，Hunan，Guangdong，
Guangxi and Guizhou Provinces of China，as well
as Vietnam in evergreen broad—leaved forests with
an altitude from 300 to 1 650 m[ 一 ．Michelia iS cy—
tologically investigated by many authors home and
abroad[5一。引．It is confirmed the group have a uni—
form chromosome 2n一38．Recently．Li et a1．[ ， ]
have a karyotype analysis on Michelia of China and
a karyotype comparison among the most genera in
Magnoliaceae． Here， however，M ． chapensis is
firstly karyomorphologically observed and some
new karyotypical characters within the genus are
found．
1 M aterial and M ethod
The plants investigated are cultivated in
W uhan Botanical Garden，The Chinese Academy
of Sciences．Shoot apices are obtained for karyo—
typical observations and the voucher specimens
Received date：2003—08—21，Accepted date：2003—10—22．
Foundation items：Chinese Academy of Sciences(KSCX2一SW一104)}WBG director fund(01035108，0105110)．
Biography：WANG Heng—Chang(1967-)，male，Ph．D．，student，focusing on plant systematics and phyt0ge0graphy(E—mail：
wanghc@rose．whiob．ac．cn)．
+ Author for c0rTesp0ndence(E—mail：jianqiangl@hotmail．com)．
E 髓鬟l I l —I I-l Ill II_l I tlI I - 1 ．FIt。t |il I I } } I l I l I I l
I l l I I l I l l l l l I I
I l I I l l f
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47O 武 汉 植 物 学 研 究 第 22卷
(Cai Q 02—012)are deposited in HIB．
Material is pretreated in a mixture of saturat—
ed aqueous solution of P—dichlorobenzene and a lit—
tle amount of bromonaphthalene for 4 h，macerat—
ed in 1：1 mixture of 1 mol／L hydrochloric acid
(HC1)at 60℃ for 6—8 min，then stained in carbol
fuchsin for 30 min and squashed in 45％ acetic
acid．More than 10 metaphase cells are counted to
determine the chromosome counts and 3 metaphase
cells are measured for karyotypical analysis．The
chromosome classification follows Levan et a1．[ 。]
and Stebbins[ standard．the karyotype asymme—
try index follows Arano[ 引．
2 Results
According to the classification standard of
Tanaka[ ZT]．interphase nuclei and prophase chro—
mosomes of M． chapensis are categorized to be
complex chromocenter type and interstitial type re—
spectively (Plate I：A，B)，the metaphase chro—
mosome counts are 2n一38(Plate I：C，D)，the
karyotype is 2n一38— 28 m+ 6 sm+4 st(2SAT)．
Chromosome morphology and karyotype are pre—
sented in Plate I：E． Karyograms are listed in
table 1 and idiogram is shown in Fig．1．The ratio
of the longest chromosome to the shortest is 2．29，
the percentage of arm ratio over 2：1 is 0．10。so
the karyotype belongs to 2B．The index of kary-
otype asymmetry is about 58．86 ，which is gen—
erally similar to those of the whole genus[ ¨ ．all
3 Discussion
of which show high degree of symmetry．Howev—
er。the most obvious difference is there are excep—
tional two pairs of st chromosomes occurred in M．
chapensis，the ratio of the longest chromosome to
the shortest value is higher than 2．00，and the
karyotype is 2B．Additionally，there is a relatively
clear pair of small satellite occurred on a pair of st
chromosome(Plate I：E，chromosome 9)．
Table 1 Karyomorphological parameters
of M ichelia chapensis
Notes：The value is based on the means of measure—
ments of the best three cells． represents
chromosome with satellite．
j 0 5
图 1 乐昌含笑的核型模式图
Fig．1 Idiogram of Michelia chapensis Dandy
Li et a1．[ ’zz]point out in Magnoliaceae the
karyotypes of Liriodendron L．and M ichelia belong
to 2A (except M．floribunda to 1A)，while the
other genera belong to 2B，and there are no st
chromosome occurred in Michelia and Tsoongioden—
dron Chun． Here M． chapensis is，nonetheless，
different from the confirmation．This，in one way，
indicates that karyotype of Michelia is not abso—
lutely uniform ，another，maybe M．chapensis has a
relatively advanced position in the whole genus．
Morphological characters of Michelia suggest that
it is a complex taxon，which comprises not only
the primitive taxa，but also the advanced taxa[z8]．
The additional occurrence of 2B karyotype infers
that in Michelia the karyotype diversity is consis—
tent with the morphological diversity．Besides，we
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第5期 王恒昌等：乐昌含笑(木兰科)的核型研究 471
think the minor structural alterations in M．
chapensis support the proposal， since there is a
very clear satellite chromosome attached on chro—
mosome 9(from Plate I：C，B，D，the satellite
chromosome can be observed consistently)，which
is probably the outcome of chromosome transloca—
tion or inversion．This needs to confirm by further
research．As Okadac ，Biswas＆Sharma[11 and Li
et a1．[2引，propose，in M agnoliaceae，some minute
heteromorphosis structural alteration occur and
they probably play a very important role in the
evolution of genus or species．
Acknowledgements：We thank Dr．Jiang Ming—Xi for
data analysis．
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472 武 祝 植 物 学 研 究 第 22卷
王恒昌等：图版 I WANG Heng—Chang el a1
． ： Plate I
技
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鳇 鬟 ) 囊
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雾耄 l q 橐 ll
15 E
耋NN ~ ,N筹 C D 嚣 桉仁难于 但染色体 内It．中期(箭头示随体)；E．枝型图(由 关话 ⋯⋯。一 巳 米 。iK
口
a
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yotyp e。f M
，
ichelia chape Dandy：A．In【 rpha。s nucleii ： mit。sLsS。mat Lc chr。m。s。mes
n M．c
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hapensist B_P ? h (Afrow sbowing satelite)．the nuc【eoI is d1ficu1t t0 be s r⋯ai⋯ned⋯,⋯bu⋯t c⋯hro⋯m⋯
SO1Ttes con fi
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n d to he nuclear membrane；c
，
D．Met㈣,oh e(Arr0w sbowing⋯
sa te
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[1it；)．2 一2 —n3t8oImEo
．
-
K aryotype of M chapensi (Ph0t0s眦 nifica{ion
：
×1 60O) ⋯ ⋯ ⋯ 一一 。 ’
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