全 文 ：五种中国苏铁属植物的核型分析*
杨志云, 龚摇 洵**
(中科院昆明植物研究所资源植物与生物技术重点实验室, 云南 昆明摇 650201)
摘要: 报道五种苏铁的染色体数目和核型, 其中红河苏铁 (Cycas hongheensis)、 叉孢苏铁 (C. segmentifida)
和十万大山苏铁 (C. shiwandashanica) 为首次报道。
关键词: 苏铁; 染色体数目; 核型
中图分类号: Q 942摇 摇 摇 摇 摇 摇 摇 文献标识码: A摇 摇 摇 摇 摇 摇 摇 文章编号: 2095-0845(2013)05-601-04
Karyotype Analysis of Five Species of Cycas (Cycadaceae) in China
YANG Zhi鄄Yun, GONG Xun**
(Key Laboratory of Economic Plants and Biotechnology, Kunming Institute of Botany,
Chinese Academy of Sciences, Kunming 650201, China)
Abstract: In this work, the chromosome numbers and karyomorphology analyses were carried out on five species of
Cycas L. from the south China. The data about C. hongheensis, C. segmentifida and C. shiwandashanica are reported
for the first time. The chromosome counts of five species are 2n=2x=22.
Key words: Cycas; Chromosome numbers; Karyomorphology
摇 Cycads ( Cycadophyta) are well鄄known living
fossils and evolutionary relicts (Nagalingum et al.,
2011), and have been inferred to be originated be鄄
fore mid鄄Permian and with peak diversification dur鄄
ing Jurassic鄄Cretaceous period ( Blackburn, 1923;
Abraham and Mathew, 1962; Arano, 1963; Chen
and Wu, 1990). The extant cycads contain three
families and 12 living genera (Chaw et al., 2005).
The Cycadaceae contains one genus Cycas with at
least 98 recognized species, which are distributed
northward to southern Japan, westward to Madagas鄄
car and the coast of Africa, southeastward to Aus鄄
tralia, and eastward to the tropical Pacific islands
(Hill et al., 2004). Southern China is the northern
distribution rim of Cycas, and as many as 27 species
were recognized by Wang and Liang (1996), some
species have been combined and only 16 species
were included in Flora of China (Wu and Raven,
1999), we followed the classification of Wang and
Liang in this study (1996).
Most Chinese species have very limited wild
distribution and all these species are protected as en鄄
dangered species in China (Fu, 1992), and a se鄄
ries of population genetics and conservation studies
have been carried out (Xiao et al., 2005; Xiao and
Gong, 2006; Zhan et al., 2011). The cytological
information including chromosome number and
ploidy level is very important information for studies
of conservation, evolution and phylogenetics. A se鄄
ries of cytological studies have been carried out on
植 物 分 类 与 资 源 学 报摇 2013, 35 (5): 601 ~ 604
Plant Diversity and Resources摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 DOI: 10. 7677 / ynzwyj201312123
*
**
Funding: The Joint Funds of the National Natural Science Foundation of China and Yunnan Provincial Government (U1136602)
Author for correspondence; E鄄mail: gongxun@ mail. kib. ac. cn
Received date: 2012-10-09, Accepted date: 2012-12-22
作者简介: 杨志云 (1975-) 女, 硕士, 主要从事植物学研究。 E鄄mail: yangzhiyun@ mail. kib. ac. cn
most China Cycas species ( Yang and Zhu, 1985;
Chen and Wu, 1990; Wu and Huang, 1999; Tian
et al., 2002; Zheng et al., 2002; Huang et al.,
2003; Qiu and Liu, 2005). We carried out cytolog鄄
ical studies on five Chinese Cycas species in this
study.
Material and methods
The collection information for five studies spe鄄
cies was listed in Table 1. All cytological materials
were collected from the southern China, and were
introduced and cultivated in Kunming Botanical Gar鄄
den. Voucher specimens were deposited at the herbari鄄
um of Kunming Institute of Botany, Chinese Academy
of Sciences (KUN).
Table 1摇 Species, localities, and vouchers of Cycas
species studied in this study
Species Locality Voucher
Cycas hongheensis Gejiu, Yunnan Tian B 0020鄄08
C. fairylakea Hezhou, Guangxi Tian B 0020鄄09
C. hainanensis Lingshui, Hainan Tian B 0020鄄11
C. segmentifida Wangmo, Guizhou Tian B 0020鄄15
C. shiwandashanica Fangchenggan, Guangxi Tian B 0020鄄17
Somatic chromosomes were prepared from the
growing root tips, pre鄄treated with 0. 05% colchi鄄
cine at room temperature for 6 h and were then fixed
in acetic alcohol (3 颐1 = absolute ethanol and glacial
acetic) at 4 益 for 30 minutes. Before staining, the
materials were hydrolyzed with 1 mol / L HCL for 15 s
at 60 益 and then were stained with a drop of car鄄
bolfuchsin and squashed before observation. Perma鄄
nent slides were made using the neutral balsam as
the mounting medium. The karyomorphological clas鄄
sification of the mitotic interphase nuclei and pro鄄
phase chromosomes followed Tanaka (1977). The
karyotypes were analyzed following Li and Chen
(1985) and each genotype was constructed arran鄄
ging the chromosomes in homologous pairs by order
of their length and arm ratio. Centromeric terminal鄄
ization value ( the abbreviation, T. C., T. C. % =
sum of the long arms / total haploid length 伊100% )
was determined according to Arano (1963) and the
asymmetry of the karyotype followed Stebbins (1971).
Results and discussion
The five Cycas species examined in this study
have a consistent somatic chromosome number of 2n
=22 (Fig. 1: C-G), which is consistent with most
previous studies ( Sax and Beal, 1934; Abraham
and Mathew, 1962; Yang and Zhu, 1985; Chen
and Wu, 1990; Wu and Huang, 1999; Tian et al.,
2002; Zheng et al., 2002; Huang et al., 2003; Qiu
and Liu, 2005). Of which, the chromosome num鄄
bers and karyomorphology of C. segmentifida, C.
hongheensis and C. shiwandashanica are reported for
the first time. All five species have simple chromo鄄
center type of interphase nucleus and interstitial type
of prophase chromosomes. However, these five spe鄄
cies have diverse chromosome karyotypes of median
(m), submedian (sm), subtermial (st) and termi鄄
nal (T) chromosome (Table 2). But, there are dif鄄
ferent in karyotypic formula: 2n=2x = 22 = 2m+4sm
+6st (4SAT)+10T (2SAT) for C. segmentifida, 2n
=2x= 22 = 4m+4sm+6st+8T (2SAT) for C. hain鄄
anensis, 2n= 2x = 22 = 4sm+6st +12T (2SAT) for
C. hongheensis, 2n = 2x = 22 = 2m +4sm +6st + 10T
(1SAT) for C. shiwandashanica and 2n = 2x = 22 =
4m + 4sm + 6st ( 2SAT) + 8T for Cycas fairylakea
(Fig. 2-3).
Table 2摇 The chromosome information of the five Cycas species
Species Karyotypic formula Karyotypictype
CT
/ %
C. segmentifida*
2m+4sm+6st(4SAT)
+10T(2SAT) 3B 85. 89
C. hainanensis 4m+4sm+6st+8T(2SAT) 3A 81. 99
C. hongheensis* 4sm+6st+12T(2SAT) 3A 85. 55
C. shiwandashanica*
2m+4sm+6st+10T
(1SAT) 3B 82. 62
C. fairylakea 4m+4sm+6st(2SAT)+8T 3B 82. 51
* New chromosome counts
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Fig. 1摇 Cytological features. A. Interphase nuclei of smooth鄄faced round prochromosomes. B. Interphase nuclei of complex chromocentre type.
C-G Mitotic metaphases. C. Cycas segmentifida, 2n=22. D. C. hainanensis, 2n=22. E. C. hongheensis, 2n=22.
F. C. shiwandashanica, 2n=22. G. C. fairylakea, 2n=22. Bar =30 滋m
Fig. 2摇 Karytotype of (C1) C. segmentifida; (D1) C. hainanensis; (E1) C. hongheensis; (F1) C. shiwandashanica; (G1) C. fairylakea
3065 期摇 摇 摇 摇 摇 摇 YANG and GONG: Karyotype Analysis of Five Species of Cycas (Cycadaceae) in China摇 摇 摇 摇 摇 摇
Fig. 3摇 Idiogram of five species of Cycas: (C2) C. segmentifida;
(D2) C. hainanensi; (E2) C. hongheensis;
(F2) C. shiwandashanica; (G2) C. fairylakea
Acknowledgements: We thank Dr. Bo Tian for his help on
the collection of samples (Kunming Institute of Botany). We
would like to thank also Mr. Xi鄄Kai Fan for helping with
scanning picture.
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