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1.
With the aim of making clear the boundaries between species in the Poa acroleucahisauchii-nipponica aggregate, chromosomes and morphological features of 746 collections gathered from 125 localities in Japan were examined.
For morphological observations, the voucher specimens of 95 collections whose chromosome numbers were reported previously
(Tateoka, 1985) were also used. Tetraploids (2n=28) and hexaploids (2n=42), as well as a few pentaploids which were the hybrids
between 4× and 6×, were found. By examining morphological features of these collections, two groups were recognized in tetraploids
and one in hexaploids. The two tetraploid groups corresponded to Poa acroleuca Steud. and P. hisauchii Honda, and the hexaploid group to P. nipponica Koidz. It was confirmed that the hairiness on the internerve surface of lemma, ligule hairiness and the length ratio of anther/
lemma are the most important features for discriminating between these species; panicle shape, leaf shape and anther length
are also helpful for the identification. The ambiguity of the boundaries between species which was hitherto present in the
taxonomy of this species aggregate was unrelated to the creation of nature itself but was attributable to the insufficiency
of our research work. 相似文献
2.
The involvement of present-day diploid bluegrass species in the formation of polyploid genomes was investigated using comparison
of sequences of internal transcribed spacers ITS1 and ITS2, and the 5.8S rRNA sequence. It was demonstrated that highly polyploid New Zealand bluegrasses, P. cita (2 n = 84; ca. 96 to 100), P. chathamica (2 n = 112), and P. litorosa (2 n 263–266) formed separate highly supported clade together with tetraploids (2 n = 28) P. intrusa, P. anceps, and P. triodioides ( Austrofestuca littoralis). Among the diploid species (2 n = 14), the closest relatives of these species, as well as of the polyploid species of section Poa, are the genomes of Eurasian species P. remota, P. chaixii (sect. Homalopoa), P. densa (sect. Bolbophorum), and P. sibirica (sect. Macropoa). Nuclear genomes of polyploid Stenopoa, Tichopoa, Oreinos, and Secundae are definitely related to the genome of Arctic species P. pseudoabbreviata (sect. Abbreviatae). On the contrary, judging by the genes for nuclear 45S rRNA, genomes of diploid P. trivialis (sect. Pandemos), P. annua, and P. supina (sect. Ochlopoa both) are only remotely related to the genomes of highly polyploid species ( p-distances between them and other bluegrass species from different sections of subgenus Poa constitute 6–10% and 11–15%, respectively). The conclusion on the relationships between highly polyploid and diploid bluegrass
species was tested using analysis of synapomorphic mutations in the 5.8S rRNA gene. It was demonstrated that genomes of Poa eminens (2 n = 42) and P. schischkinii (2 n = 70) (sect. Arctopoa both) were noticeably different in ITS regions from the genomes of the members of the type subgenus Poa. A comparison of the Arctopoa ITS regions showed that the differences between them constituted only 0.2%. At the same time, p-distances between the Arctopoa ITS and those from the species belonging to other sections of the genus Poa varied from 5 to 14%. South American species P. chonotica (sect. Andinae) (= Nicoraepoa chonotica) (2 n = 42) was found to be related to Arctagrostis, Festucella, and Hookerochloa, being at the same time quite distant from the other species of the genus Poa. Polymorphic in chromosome number highly polyploid species of Northern Hemisphere, P. arctica (2 n = 42 to 106), P. turneri (2 n = 42, 63 to 64), and P. smirnowii (2 n = 42, 70) (sect. Malacanthae) are relative to a large group of tetraploid (2 n = 28) endemic bluegrass species from New Zealand and sub-Antarctic islands ( P. novaezelandiae and allied species). 相似文献
3.
The Poa laxa Haenke species group, comprising four alpine –arctic taxa in P. sect. Oreinos, has a complicated and confusing taxonomic history. Here we re‐examine the taxonomy of the group and section based on sequences of three plastid and two nuclear ribosomal DNA markers. Poa laxa s.l. resolved in a clade with species of sections Abbreviatae, Oreinos, Stenopoa, and Tichopoa. In the plastid analyses, Poa laxa s.s. (type of sect. Oreinos) was placed in a subclade with P. glauca and other sect. Stenopoa species, while all other P. laxa s.l. taxa were placed in a subclade with species of sect. Abbreviatae. We maintain P. laxa s.s. (mainly 2n = 28) of west–central Europe in sect. Oreinos, while the other P. laxa s.l. taxa from northern Europe and North America (all 2n = 42 or higher ploid) are referred to P. sect. Abbreviatae. In North America only one collection of the northern European P. flexuosa subsp. flexuosa is accepted (Greenland, Jensen's Nunatakker), and P. flexuosa subsp. fernaldiana is accepted based on populations in eastern Canada and northeast USA. A new subspecies, P. flexuosa subsp. consauliae, is described from eastern Arctic Canada and Greenland ; its variable morphological characteristics suggest introgression with P. glauca and it is predicted to be apomictic. Rocky Mountain P. laxa subsp. banffiana is treated as P. banffiana. Oregon material formerly considered to belong to P. laxa s.l. is named P. wallowensis. Poa sect. Oreinos is thus found to be polyphyletic, and is here emended to comprise only three continental European species, including P. laxa. Lectotypes are designated for P. aspera var. laxiuscula, P. fernaldiana, P. flexuosa, and P. laxa var. debilior. New chromosome numbers are reported for P. flexuosa subsp. consauliae (ca 2n = 42), and P. glauca (2n = 63) from Baffin Island. A key to the species and subspecies found in North America is given. 相似文献
4.
To explore the cytogenetical relationships of Elymus and Agropyron of the tribe Triticeae, Gramineae, two species of Asiatic Elymus, E. sibiricus (2n=28) and E. dahuricus (2n=42), and a Japanese Agropyron, A. tsukushiense (2n=42) were crossed. Pentaploid and hexaploid F 1 hybrids were vigorous. All pollen grains were aborted and none of the hybrids produced seed.
For the cross E. sibiricus × A. tsukushiense, the average chromosome pairing per cell at the MI of the PMCs in the F 1 was 16.38 univalents, 8.93 bivalents, 0.25 trivalents and 0.01 quadrivalents; for the cross E. dahuricus × A. tsukushiense, it was 4.41 univalents, 17.67 bivalents, 0.32 trivalents, 0.28 quadrivalents and 0.04 quinquevalents; and for the cross E. dahuricus × E. sibiricus, it was 17.11 univalents, 8.74 bivalents, 0.04 trivalents and 0.07 quadrivalents. From the present results, it is concluded
that E. sibiricus contains one genome and E. dahuricus contains two genomes, which are homologous to those of A. tsukushiense, and that the third genome of E. dahuricus might be partially homologous to the remaining genome of A. tsukushiense. This conclusion is also supported by the cytogenetical analysis of E. dahuricus × E. sibiricus.
Contribution No. 27 from the Plant Germ-plasm Institute, Faculty of Agriculture, Kyoto University, Kyoto, Japan. 相似文献
5.
An attempt was made to investigate some populations of the Poa macrocalyx complex in eastern Hokkaido in relation to the taxonomy of this complex. Individual specimens preserved in TI, KYO and TNS
were also studied. Chromosome counts of 2n=42 were obtained in the majority of a total of 84 collections, and counts of 2n=63
(incl. ca. 63), ca. 70 and 84 were also made in a few collections. High percentages of viable pollen were observed. The morphological
features which were designated by previous authors to be significant in separating Poa sachalinensis from P. macrocalyx and in discriminating between the varieties of P. macrocalyx were critically examined with emphasis on the observations of infra-population variation. It was confirmed that (1) the populations
of the Poa macrocalyx complex in eastern Hokkaido are greatly variable morphologically and are also in a dynamic state cytogenetically, (2) plants
of this complex in eastern Hokkaido belong to one and the same species, P. macrocalyx, and the varieties fallax, scabriflora and tatewakiana may be merely morphs, and (3) some plants which are somewhat different from the plants in eastern Hokkaido with respect to
glume features are distributed in Sakhalin, and northern and central Hokkaido. Some problems which should be subjected to
further studies are pointed out. 相似文献
6.
The chromosome numbers of forty-one Brazilian species belonging to 11 genera of preferentially terrestrial orchids (subfamilies Cypripedioideae, Spiranthoideae, Orchidoideae, and Vanilloideae) were examined. Previous records for these subfamilies were reviewed in order to identify the ancestral chromosome numbers of terrestrial orchids. The variation observed within the subfamilies Spiranthoideae (2n=28, 36, 46, 48 and 92), and Orchidoideae (2n=42, 44, ca. 48, ca. 80, 84, and ca. 168) was similar to that previously reported in the literature. In the subfamily Spiranthoideae, some species of Prescottia (subtribe Prescottiinae) and some genera of Spiranthinae showed a bimodal karyotype with one distinctively large pair of chromosomes. The analysis of chromosome numbers of the genera in subfamilies revealed the predominance of the polyploid series 7, 14, 21, 28, 42 with a dysploid variation of ±1 in each ploidy level. These results suggest that the basic chromosome number of terrestrial orchids is x 1=7 for the subfamilies Spiranthoideae and Orchidoideae, as well as other Epidendroid orchids, and that the majority of the genera are composed of palaeopolyploids. 相似文献
7.
The involvement of present-day diploid bluegrass species in the formation of polyploid genomes was investigated using comparison of sequences of internal transcribed spacers ITS1 and ITS2, and the 5.8S rDNA sequence. It was demonstrated that highly polyploid New Zealand bluegrasses, P. cita (2n = 84; ca. 96 to 100), P. chathamica (2n = 112), and P. litorosa (2n = 263 to 266) formed separate highly supported clade together with tetraploids (2n = 28) P. intrusa, P. anceps, and P. trioides (Austrofestuca littoralis). Among the diploid species (2n = 14), the closest relatives of these species, as well as of the polyploid species of section Poa, are the genomes of Eurasian species P. remota, P. chaixcii (sect. Homalopoa), P densa (Bolbophorum), and P. sibirica (sect. Macropoa). Nuclear genomes of polyploid Stenopoa, Tichopoa, Oreinos, and Secundae are definitely related to the genome of Arctic species P. pseudabbreviata (sect. Abbreviatae). On the contrary, judging by the genes for nuclear 45S rRNA, genomes of diploid P. trivialis (sect. Pandemos), P. annua, and P. supina (sect. Ochlopoa both) are only remotely related to the genomes of highly polyploid species (distances p between them and other bluegrass species from different sections of subgenus Poa constitute 6-10% and 11-15%, respectively). The conclusion on the relationships between highly polyploid and diploid bluegrass species was tested using analysis of synapomorphic mutations in the 5.8S rRNA gene. It was demonstrated that genomes of Poa eminens (2n = 42) and P. schischkinii (2n = 70) (sect. Arctopoa both) were noticeably different in ITS regions from the genomes of the members of the type subgenus Poa. A comparison of the Arctopoa ITS regions showed that the differences between them constituted only 0.2%. At the same time, p distances between the Arctopoa ITS and those from the species belonging to other sections of the genus Poa varied from 5 to 14%. South American species P chonotica (sect. Andinae) (=Ncoraepoa chonotica) (2n = 42) was found to be related to Arctagrostis, Festucella, and Hookerochloa, being at the same time quite distant from the other species of the genus Poa. Polymorphic in chromosome number highly polyploid species of Northern Hemisphere, P. arctica (2n = 42 to 106), P. turneri (2n = 42, 63 to 64), and P. smirnovii (2n = 42, 70) (sect. Malacanthae) are relative to a large group of tetraploid (2n = 28) endemic bluegrass species from New Zealand and sub-Antarctic islands (P. novae-zelandiae and allied species). 相似文献
8.
Chromosome numbers are determined from 37 populations attributed to 22 taxa of Japanese Arisaema. Of them, chromosome numbers of A. limbatum var. conspicuum (2 n=26), A. minus (2 n=26), A. nambae (2 n=28) and A. seppikoense (2 n=26) are determined for the first time. New chromosome numbers, 2 n=26, are reported for A. aequinoctiale, A. limbatum, A. stenophyllum, A. undulatifolium and A. yoshinagae. Three modes of basic chromosome numbers, x=14, x=13 and x=12, occur in Japanese Arisaema. Precise karyotypic comparisons of 20 taxa reveal that taxa with x=14 and x=13 share 26 major chromosome arms and have an obvious chromosomal relationship. One of two submeta-centric chromosomes in x=13 corresponds to two telo-centric chromosomes in x=14. In A. ternatipartitum with 2 n=6 x=72, ten out of 12 basic chromosomes are the most similar in size and arm ratio with larger ten chromosomes of A. ringens among Japanese Arisaema examined. A basic chromosome number of x=14 is the commonest in the genus Arisaema and the remaining basic chromosome numbers, x=13 and x=12, seem to be derived through dysploidal reduction by translocating large segments of major arm of telo-centric chromosome
onto other minor arm of telo-centric followed by loss of the remainings including a centromere, and by loss of two telo-centrics
from x=14, respectively. Some systematic problems of Japanese Arisaema are discussed based on new cytological data. Arisaema hatizyoense, A. minus and A. nambae are accepted as independent species. 相似文献
9.
Meiotic pairing behaviour in 19 interspecific Elymus hybrids is reported and discussed. The hybrids were made between four species belonging to the E. semicostatus group of sect. Goulardia, viz., E. semicostatus, E. abolinii, E. fedtschenkoi, and E. panormitanus (all 2n = 28), and Elymus species of seven different sections, viz., sect. Clinelymiopsis: E. caucasicus (2n = 28); sect. Elymus: E. sibiricus (2n = 28); sect. Goulardia: E. caninus (2n = 28), E. trachycaulus (2n = 28), and E. tsukushiensis (2n = 42); sect. Hyalolepis: E. batalinii (2n = 42); sect. Hystrix: E. hystrix (2n = 28); sect. Macrolepis: E. canadensis (2n = 28); and sect. Turczaninovia: E. dahuricus (2n = 42). Chromosomal pairing at meiotic metaphase I indicated that the species of the E. semicostatus group are genomically closer to the tetraploid E. caucasicus and the hexaploid species, regardless of sectional origin, than to the other tetraploid species of section Goulardia. Highest meiotic pairing was found in hybrids involving E. caucasicus, E. tsukushiensis, and E. dahuricus. The presence of pairing regulating genes in E. abolinii is suspected. 相似文献
10.
Karyomorphological comparisons were made of 16 native and cultivated species of Selaginella in Japan. The somatic chromosome numbers are 2n=16 in S. boninensis; 2n=18 in S. doederleinii, S. helvetica, S. limbata, S. lutchuensis, S. nipponica, S. selaginoides, S. tama-montana, and S. uncinata; 2n=20 in S. biformis, S. involvens, S. moellendorffii, S. remotifolia, and S. tamariscina; 2n=30 in S. rossii; and 2n=32 in S. heterostachys. The interphase nuclei of all species examined are uniformly assigned to the simple chromocenter type. The metaphase karyotype
of 2n=16 (x=8) is 8 m (=median centromeric chromosomes)+8(st+t)(=subterminal and terminal). The group of the species having
2n=18 (x=9) is heterogeneous karyomorphologically: The karyotype of S. nipponica is 2n=18=6 m+12(st+t), S. tama-montana 10 m+2 sm(=submedian)+6(st+t), and S. uncinata 6 m+7 sm+5(st+t). Although the remaining five species have the common karyotype 8 m+4 sm+6(st+t), the values of mean chromosome
length are variable. Another group of the specles having 2n=20 (x=10) is homogeneous, since all species have the same karyotypes
8 m+4 sm+8(st+t) and have similar chromosome size. The karyotype of 2n=30 is 12 m+6 sm+12(st+t) and is suggested to be a triploid
of x=10, and 2n=32=16m+16(st+t), a tetraploid of x=8. Thus, three kinds of basic chromosome numbers, x=8, 9, 10 are present
in Japanese Selaginella examined, and their karyomorphological relationships are discussed. 相似文献
11.
First generic chromosome counts reveal the base number x=7 for the genera Tetrameranthus and Rollinia. T. umbellatus from the Peruvian Amazon is diploid (2n=14), T. duckei from Brazil (Manaus) is tetraploid (2n=28). In the Neotropics Rollinia (7 species counted) has developed diploid to octoploid taxa (2n=14, 28, 42, 56). Counts of 7 South American Annona species are presented for comparison (2n=14, 28). The West African Cleistopholis patens has 2n=14. The Asian genus Mezettia: 2n=14 and the neotropical Guatteria tribe: 2n=28 are also revised. A detailed karyomorphological comparison, including karyotypes, banding patterns, condensing behaviour of chromosomes and structure of interphase nuclei reveals that the closely related genera Annona and Rollinia are almost identical in their diploid genomes, whereas the polyploid ones differ in their heterochromatin (=hc) composition and number of NO-chromosomes. Cleistopholis, Mezettia and the Guatteria tribe are karyologically and systematically distinct from each other and from Annona/Rollinia. Tetrameranthus as compared with the karyomorphology of about 60 other Annonaceous genera has a very peculiar and unusual karyomorphology which underlines its isolated position. Nuclear structures are almost identical in the African genus Uvariopsis (2n = 16) and partly similar in the Guatteria tribe; both also share some morphological similarities and possibly are related. From a comparison of Tetrameranthus with several nuclear types within the Magnoliidae, a new model of chromosome evolution in primitive Angiosperms is suggested. In respect to their eco-morphological differentiation the genera investigated differ strongly from each other.Dedicated to Prof. Dr. K.-H. Rechinger on the occasion of His 80th birthday. 相似文献
12.
为探究凤仙花近缘种植物的细胞学和微形态学方面的亲缘关系,该文选取荔波凤仙花(Impatiens liboensis)及近缘种赤水凤仙花(I.chishuiensis)和管茎凤仙花(I.tubulosa)的根尖和叶表皮为实验材料,采用体细胞染色体常规压片法和叶表皮光学显微镜观察法对凤仙花近缘种植物进行染色体及叶表皮特征研... 相似文献
13.
A chromosome survey of Poa macrocalyx growing on the coast of Hokkaido was carried out. Counts were made for 619 samples collected from 37 populations. A large
variation in the chromosome numbers (2n=42-2n=87) was disclosed, and on the basis of this and some other observations, this
species was presumed to represent an apomictic polyploid complex. Three main cytotypes with 2n=42, 2n=49 and 2n=68 were discovered.
They differed in their geographical distribution. Plants with 2n=70 and 2n=77 appeared to a considerable extent, but it could
not be ascertained whether they were good “races”. Other plants with diverse chromosome numbers, and in some cases only ephemeral,
were also sporadically detected. Infrapopulational variation was scarce in some populations while fairly common in some others.
Uneven segregation of chromosomes at meiosis and the fusion of reduced and unreduced gametes seemed to be the main factors
contributing to chromosome fluctuations within a population. 相似文献
14.
Summary
Stellaria media and Poa annua were grown in a greenhouse over a wide range of mixed densities, and at three nutrient levels. The relative performances and interactions between individuals of both species were assessed over four interharvest growth periods using a new approach based on response functions (Connolly 1987). Species relative performances and interactions were complex, varying through time, and with mixed density and the nutrient environment. Studying the dynamics of the individual, interharvest growth periods led to a different, more accurate mechanistic interpretation of the final yield results, than did studying only one overall period of growth. Starting from considerably smaller seeds, Stellaria averaged twice as much biomass as young Poa plants by harvest 2 (H2). Stellaria achieved this early dominance with little suppression of Poa. Interspecific interference became more significant, and species proportional growth (K) became more similar in the second interharvest period (H2-3). During the final period of growth (H3-4), species relative performances largely reversed, Poa showing greater proportional growth than Stellaria. This superior performance by Poa occured despite individual plants being, on average, one half the size of Stellaria. Lack of interference early on is attributed to complementary above ground resource use resulting from species different shoot architectures (prostrate vs. cespitose). This complementarity disappeared as plants aged and became larger. The decline in Stellaria's superior relative growth performance through time was mainly due to its earlier and more substantial diversion of resources to reproduction. Species perception of each others influence, relative to themselves, as quantified by substitution rates, varied with both mixed density and nutrient environments. Stellaria consistently perceived Poa as less influential at higher nutrient levels than at lower levels. High nutrients favored the production of biomass for Stellaria more than for Poa, particularly in H2-3. While accelerating the switch to reproduction for Stellaria, nutrients did not increase its final reproductive yield per unit biomass. After H2, proportional growth for both species was relatively independent of frequency and density, indicating that a species acted as an aggregate of similarly behaving units of biomass whether arranged on many small, or a few large plants. An example shows that the conclusions from the response function approach applied within can be qualitatively different from those derived from a substitutive approach such as replacement series. 相似文献
15.
The five annual species of Adonis L., sect. Adonis, growing in Israel, form a series of diploid, tetraploid and hexaploid species. Their somatic chromosome numbers are 2n = 16 in A. annua L., A. dentata
Del. and A. palaestina
Boiss., 2n = 32 in A. microcarpa DC., 2n = 48 in A. aestivalis L.; counts for A. dentata, A. palaestina and A. microcarpa are new records. There are indications that alloploidization may have been involved in the process of speciation in sect. Adonis. A taxonomic survey of the 8 species of the section reveals that a higher ploidy level is usually combined with a larger distribution area. 相似文献
16.
Despite extensive interest in the role of plant size in competition, few formal attempts have been made to quantify the magnitude of asymmetric competition, particularly for interactions between members of different species. This paper introduces the concept of asymmetric interspecific competition at the population livel (i.e. mean plant performance) in mixtures of species. It proposes an index of interspecific competitive asymmetry which allows for a progressively greater asymmetric effect as the average size differences between competing species increase, and allows for such an effect whether individuals of focal species are larger or smaller, on average, than competitors. This index of competitive asymmetry is evaluated in the study of interactions between two widely coexisting annuals of disturbed habitats, Stellaria media and Poa annua. An experiment was conducted in which the density, relative frequency and relative seedling sizes (emergence times) of Poa and Stellaria individuals were varied. The relative growth rate (RGR) for both species was measured over a 22-day period. An inverse linear model was fitted for each species, relating the RGR of the focal species to the initial biomass of each species. Each response model included an asymmetry coefficient () to assess whether the impact of a unit of initial biomass of the associate species changed with the relative sizes of seedlings of the two species. A zero value of implies symmetric competition between the two populations; i.e. the competitive effect of a unit of associate species biomass does not change with its initial seedling size. If is positive the smaller the initial relative size of seedlings of the associate species, the smaller their per unit biomass effect on the response of the focal species. The model fitted our data for Stellaria and Poa well and was validated by an alternative modelling approach. Asymmetry coefficients were estimated as 0.508 ( P<0.05) for the effect of Poa in the Stellaria model, and 0.0001 (NS) for the effect of Stellaria in the Poa model; i.e. the effect of Poa on Stellaria was asymmetric while the effect of Stellaria on Poa was symmetric. Differences in interspecific species asymmetric competitive effects are discussed within the context of shoot architecture, and the relative importance of competition for light versus soil resources. Finally, we discuss the relationship of this model to earlier models of competitive asymmetry, and consider the implications of interspecific competitive asymmetry for a number of current theories of plant competition and community organisation. 相似文献
17.
The chromosome numbers of several species of Zamia from Mexico are reported. Z. paucijuga, distributed from central Oaxaca to Nayarit, has been found to have 2n = 23, 25, 26, 27 and 28. 2n = 28 is the highest chromosome number yet found in the cycads. Karyotypes of this species differ principally in the number of telocentric and metacentric chromosomes present in each; 2n = 23, 25, 26, 27 and 28 were found to have 5, 3, 2, 1 and 0 metacentric and 8, 12, 14, 16 and 18 telocentric chromosomes, respectively. Z. fischeri has been found to be 2n = 16, Z. furfuracea and Z. loddigesii 2n = 18. Zamia paucijuga on the basis of morphological and ecological characteristics, is considered to be an advanced member of this genus. Chromosome and karyotype evolution in Z. paucijuga may have occurred by centromeric fission of metacentric chromosomes; the karyotypes of Z. paucijuga are strongly asymmetrical, suggesting that they evolved recently. 相似文献
18.
Further chromosome counts, principally from the southeastern United States, are reported for 38 accessions of 11 species, together with new or corrected counts forP. nudum (2n = 40),P. montanum (2n = 40),P. curvipes (2n = 40), andP. torrei (2n = 80). Four species have now been shown to have intraspecific polyploidy, five are known only as diploids, and nine occur only at the tetraploid level. Artificially produced interspecific hybrids range from vigorous to dwarfed or nonflowering, and from semifertile to sterile as measured by anther development and stainable pollen. Naturally occurring hybrids are described for the following species combinations:P. clinopodioides ×P. incanum,P. pilosum ×P. virginianum, P. flexuosum ×P. nudum, andP. albescens ×P. loomisii. 相似文献
19.
Chromosome counts for 783 collection of Calamagrostis in Japan are reported. These include the first record for C. tashiroi and the reports of new cytotypes in C. stricta, C. hakonensis and C. longiseta. The geographical distribution of different cytotypes of C. langsdorffii and C. hakonensis is outlined. Counts are also reported for a number of “intermediates” which are supposed to be interspecific hybrids or hybrid
derivatives. A summary of chromosome counts for Japanese Calamagrostis so far recorded is tabulated. No diploid plants with 2n=14 chromosomes are found. The tetraploid taxa, which are plentiful
and seem to have adaptively radiated in Japan, jack any sign suggestive of their recent origin from the diploids. It is suggested
that plant with 2n=28 (4X in the traditional sense) may be regarded as semidiploid and having that behavior, and that speciation
of Calamagrostis in Japan has occurred principally at this chromosome level. Speciation by means of amphiploidy may have been scarce. It is
also suggested that hybridization and polyploidy have greatly contributed to the formation of complicated internal structure
of various species. 相似文献
20.
采用常规压片法,对风毛菊属(Saussurea)5种植物的染色体数目和核型类型进行分析。结果表明:大耳叶风毛菊(S.macrota)核型公式为2n=2x=26=10m+12sm+4st,属2A型;长梗风毛菊(S.dolichopoda)核型公式为2n=2x=26=14m+8sm+4st,属2A型;川陕风毛菊(S.licentiana)核型公式为2n=2x=28=12m+16sm,属2B型;杨叶风毛菊(S.populifolia)核型公式为2n=2x=28=6m+18sm+4st,属2B型;尾叶风毛菊(S.caudata)核型公式为2n=2x=30=14m+14sm+2st,属2A型。这5种风毛菊属植物中,除大耳叶风毛菊染色体数目和核型类型与前人报道的一致外,其余4种植物的染色体数目和核型类型均为首次报道,并在川陕风毛菊中发现1对B染色体。 相似文献
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