全 文 ：第 20 卷　第 3 期　　　　　　　木　　本　　植　　物　　研　　究 2000 年　7 月
Vol.20　No.3　　　　　　　BULLETIN OF BOTANICAL RESEARCH July , 　2000
款冬属的核形态(菊科:千里光族)
刘建全
(中国科学院西北高原生物研究所 , 西宁 810001 ,青海)
摘　要　研究了款冬属的核形态。染色体间期为简单型与复杂型的过渡型;前期染
色体为近基型与中间型的过渡型。染色体较小 ,核型不对称 ,具明显的二型性;数目
与核型公式为 2n=60=42m+10sm+6st+2t。比较发现款冬的核型明显不同于千
里光族中已有的核型记载 ,其核型特征似乎与它独特的形态特征相联系 ,具有重要
的系统学意义 。
关键词　款冬属;千里光族;核形态
KARYOMORPHOLOGY OF TUSSILAGO L.
(ASTERACEAE:SENECIONEAE)AND
ITS SYSTEMATIC SIGNIFICANCE
LIU Jian-quan
(Nor thwest P lateau Institute of Biolog y , the Chinese Academy of Science , Xining 810001)
Abstract　Investigated in the present paper w as the karyomorphology of Tussi lago L.
The interphase nuclei w ere categorized to be the intermediate type between the simple
chromocenter type and complex chromocenter type , and the mitotic prophase chromo-
somes were classified as the intermediate type betw een the proximal type and intersti-
tial type.The metaphase chromosomes were rather small , ranging f rom 2.67μm to 1.
05μm and the average leng th w as 1.37μm.The karyo type w as formulated as 2n=60
=40m+8sm+10st+2t w ith distinct bimodali ty.The karyomorphological characteris-
tics of Tussilago are disctinct f rom those of other genera reported in the Senecioneae
and seem to be correlated to it s unique g ross mo rphology .
Key Words　Tussi lago;Senecioneae;Karyomorphology
Tussi lago L., a mono typic genus of the tribe Senecioneae in the Asteraceae , occurs w ide-
作者简介:刘建全(1969-),男 ,博士 ,副研究员 ,从事系统与进化植物学。
Supported by the President Foundation of the Chinese Academy of Sciences and the Natural National S ciences Foundation of
China(39670059).收稿日期:1999-7-29
ly in Eurasia.Karyomo rphological characters are of utmost importance for elucidating the phy-
logeny and evolut ion of the Asteraceae[ 1] , especially for the subdivision of the tribe
Senecioneae[ 2 ,3] , but the karyotype of Tussi lago , except it s chromosome number being report-
ed to be 2n=60 several t imes f rom different localit ies[ 4 ～ 8] , has not been reported yet.The
karyomo rphology of Tussi lago was reported and its sy stematic significance was discussed in the
present paper.
1　Material and Methods
The roots of Tussilago farfara were collected in Xining , Qinghai Province , China.The
voucher specimen (Liu Jian-quan 354)was deposited in Northwest Plateau Institute of Biolo-
gy , the Chinese Academy of Sciences(HNWP).
The root tips were pretreated in the mix ture of 0.1% colchicine and 0.002 mol/L hydrox-
yquinoline fo r tw o hours , and then fixed overnight in the fixative (1:3 glacial acet ic acid and
absolute alcohol).They w ere macerated in 1 mol/L HCl at 60℃ for five minutes , and stained
and squashed in Carbol Fuschin solutions before observation.The karyo type formula was based
on the measurements of mitotic metaphase chromosomes.The karyomorphological classif ica-
tions of the resting and mito tic prophase int roduced by Tanaka[ 9] , the symbols fo r cent romeric
posit ions def ined by Levan et al.[ 10], the index of relative length suggested by Kuo[ 11] and the
classification of karyotype asymmetry of Stebbins[ 12] were followed.
2　Result
In the resting nuclei(Plate I:1), several darkly herteropycnotic bodies were observed.
The boundary of the bodies w as rather indistinct and chromatin surrounding appeared to diffuse
g radually .Thus the karyomo rphology of resting nuclei w as the intermediate type betw een the
simple chromocenter type and complex chromocenter type.In the prophase chromosomes
(Plate I:2), the heterochromatic segments were mainly distributed in pro ximal regions of both
arms , but w ere indistinct ly found in distal and interstitial regions.Therefore , the prophase
chromosomes were classif ied as the intermediate type between the pro ximal type and interstitial
type.
The metaphase chromosomes were counted to be 2n=60 (Plate I:3), ranging from 2.
67μm to 1.05μm in leng th(Plate I:4).The average length w as 1.37μm.The karyotype w as
formulated as 2n=60=42m+10sm +6st+2t;no secondary const riction w as detected.The
relative leng th w as formulated as 2n=18=6L+14M 2+38M1 +2S.The karyo type was cate-
go rized as Stebbins 2B type.
3　Discussion
The chromosome number of 2n = 60 of Tussilago is here reconfirmed.In the tribe
Senecioneae , the chromosome numbers have been recorded for most genera[ 2] , and tw o majo r
basic chromosome numbers are found:x =10 and x=30.Based on the basic chromosome num-
314 木　本　植　物　研　究　　　　　　　　　　　　　　　20 卷
bers , as well as the morphological characters , tw o major evolutionary lineages(senecionoid and
tussilaginoid)have long been recognized in the t ribe Senecioneae[ 2 , 3 , 13 ～ 15] .The senecionoid
lineage is characterized by chromosome numbers of x=10 or 20 or numbers derived theref rom ,
as well as style branches wi th separate stigmatic lines , upper stamen filaments w ith swollen col-
lars and anthers often w ith thickening in the lateral w alls of the endothecial cells.In the tussi-
laginoid lineage , the chromosome numbers are based mostly on x =30 or numbers derived
theref rom , the st igmat ic surfaces is enti re o r nearly so across the inner face of the style branch ,
the upper stamen f ilaments are cylindrical and the anthers of ten have thickenings in the t rans-
verse w alls of the endo thecial cells.Tussilago , as w ell as the genera Ligularia , Parasenecion
and Farfugium etc.with x=30 , belongs to the tussilaginoid lineage.
Table 1Parameters of mitotic metaphase chromosomes of Tussi lago farf ara
NO RL AR T IRL No RL AR T IRL
1 1.45+4.84=6.29 3.34 st 1.89 16 1.50+1.69=3.19 1.13 m 0.97
2 1.21+4.11=5.32 3.40 st 1.60 17 1.45+1.60=3.05 1.10 m 0.91
3 1.31+2.90=4.21 2.21 sm 1.26 18 1.35+1.60=2.95 1.19 m 0.89
4 1.69+2.42=4.11 1.43 m 1.23 19 1.26+1.64=2.90 1.30 m 0.87
5 1.26+2.56=3.82 2.03 sm 1.19 20 1.21+1.69=2.90 1.40 m 0.87
6 1.60+2.13=3.73 1.33 m 1.12 21 1.16+1.74=2.90 1.50 m 0.87
7 0.82+2.71=3.53 3.30 st 1.06 22 1.06+1.79=2.85 1.69 m 0.86
8 1.26+2.18=3.44 1.73 sm 1.03 23 1.21+1.64=2.85 1.36 m 0.86
9 1.11+2.27=3.38 2.05 sm 1.02 24 1.11+1.74=2.85 1.57 m 0.86
10 1.50+1.84=3.34 1.23 m 1.00 25 1.06+1.74=2.80 1.64 m 0.84
11 1.45+1.84=3.24 1.27 m 0.99 26 1.00+1.79=2.79 1.79 sm 0.84
12 1.40+1.84=3.24 1.31 m 0.97 27 1.26+1.50=2.76 1.19 m 0.83
13 1.55+1.69=3.24 1.09 m 0.97 28 1.21+1.50=2.71 1.24 m 0.81
14 0.20+3.04=3.24 15.0 t 0.97 29 1.21+1.45=2.66 1.19 m 0.80
15 1.50+1.69=3.19 1.06 m 0.97 30 1.21+1.26=2.47 1.04 m 0.74
RL:relative leng th;AR:arm ratio;T:ty pe;IRL:index of relative leng th
However , in his systematic revision of the Chinese Asteraceae , Ling[ 16] rejected these two
evolutionary lineages.He thought the genera of the tussilaginoid lineage are not a natural group
and treated the tussilaginoid genera in three subtribes:Subtrib.Tephroseridinae , Ligulariinae
and Tussilagininae.The subtribe Tussilagininae(s.s.)includes only tw o genera:Tussi lago
and Petasi tes , and is closer to his subtribe Crassocephalinae of the senecionoid lineage (with x
=10)than to his subtribes Liguriinae(x =30)and Tephroseridinae(x=23 , 24);the lat ter
tw o subtribes together w ith Tussilago and Petasites comprise the natural tussilaginoid lineage
acco rding to Robinson et al.[ 2] , Bremer[ 3] and Jeff rey[ 13] .
3153 期　　　　　　　　　刘建全:款冬属的核形态(菊科:千里光族)
The kary otype analy ses in the Senecioneae are only limited to a few genera occurred in
Japan[ 17 ,18] .The studied genera can be ascribed to the above tw o evolutionary lineages:
Senecio and Erechti tes with x =10 belonging to the senecionoid lineage and Ligularia ,
Parasenecio and Farf ugium with x=30 belonging to the tussilaginoid lineage.Their observa-
tions indicated there rarely existed karyotype dif ferentiation among the studied genera even be-
tween the g roups w ith rather dif ferent basic numbers:x=10 and x=30.All karyotypes consist
of median , submedian and subtelenic chromosomes w ithout bimodality.The chromosome
leng ths are relat ively large varying between 3 ～ 7μm .Compared with these genera (Senecio ,
Erechti tes , Ligularia , Parasenecio and Farfuf ium), Tussi lago dif fers karyomo rphologically
from them in the rather small chromosomes(2.67 ～ 1.05μm), bimodal and rather asymmetri-
cal karyotypes.Acco rding to S tebbins[ 12] and compared w ith the outg roup (Astereae , a tribe
closely related to the Senecioneae), these karyomorphological characteristics should be derived.
They seem to be correlated w ith the advanced morphology of Tussi lago:trimorphological flow-
ers and flow ers precocious.To a extent , the present observation seems to support the t reatment
provided by Ling(1997)that Tussi lago and Petasites should be separated f rom the other gener-
a of the tussilaginoid lineage.But another possibili ty is that there might exist an early kary-
otype differentiation among the genera of the tussilaginoid lineage.However , up to now , no
karyo type information is available for Petasites and most genera of tussilaginoid lineage.There-
fore , unt il a more extensive survey of karyomorphology on the tribe Senecioneae is completed ,
i t is st ill unclear w hether Tussilago and Petasi tes should be recognized at the subtribe level
(Tussilaginiae s.s.as circumscribed as by Ling[ 16])unrelated to the o ther tussilaginoid genera
o r retained as a early diverging branch of the tussilaginoid lineage(Tussilaginiae s.l.).In other
w ords , i t can not be determined whether the genera of the tussilaginoid lineage comprise a
monophy legenetic group or not.We hope molecular sy stematic studies of the t ribe Senecioneae
currently underway can provide additional information to assist in solving the above questions.
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Explanation of plates
1.The resting nuclei;2.The prophase chromosome;3.The metaphase chromosomes;
4.Karyotype.-Bar=10μm
　　　　　　　　　
　　　　　
　　　　
　　　　
3173 期　　　　　　　　　刘建全:款冬属的核形态(菊科:千里光族)