E.O.Punina, T.V.Alexandrova

chromosome volume and relative DNA - ++ capacity of Caucasian Representatives of the species Paeonia (Paeoniaceae)

Botanicheskij journal 1992 11:16-23

Translation from the Russian of Dr.Carsten Burkhardt, Cottbus


The relative DNA content in 11 species of Paeonia (Paeoniaceae) which determined. A direct non - linearly dependence between DNA content and mitotic chromosome volume which demonstrated in the diploid species (2n=10) and the tendency for decrease in DNA content with specialisation of the species which shown. There is no regular pattern of DNA content variation among tetraploid species. Based on the DNA content the identity of P.ruprechtiana (2n=10) is discussed.

In latter time essential variabilitys in the DNA - capacity were demonstrated different Taxonome bedecktsamiger plants (Rothfels et al., 1966; Bennet, Smith, 1976; Narayan, Rees, 1976 among others). Frequent was that joined with a change the chromosome number, for example as result a Polyploidisierung or [Anei-ploidisierung]. Thereby were shown considerable sway in the DNA - capacity at species with equal chromosome number (Sparrow, Miksche, 1961; Rees et al., 1966; Rothfels et al.,1966; Zakirova, Vakhtina, 1974; Jones, Brown, 1976; Vakhtina et al., 1977). In a series of cases was shown, that that called forth became through reconstructions of chromosomes, how for example at the species Crepis(Jones, Brown, 1976) and Bulnesia(Fam. Zygophyllaceae) (Poggio et al.1978) or through changes at the rate of Hetero - ++ to Euchromatin, like in the species Scilla(Greilhuber, 1979).

At the investigation the karyotypes of the Caucasian representatives of the species Paeonia(Punina, 1987) was demonstrated, that the species of this species with a chromosome number of 2n=10 (i.e. diploide) display very similar karyotypes. If one compares the relative length of the chromosomes, are the karyotypes all diploid practically identical. Solely at the measurement of the parameters of the chromosomes (in mm) significant differences emerged between the karyotypes. So was at P.mlokosewitschi the summed up length the haploiden of set of chromosomes 140.6mm, the thickness of the chromosomes 1.64mm and the Gesamtvolumen the diploid of sentence 148.8mm³, at P.tenuifolia totaled these parameters 111.0, 1.23 and 65.9mm. At a differential staining of the Caucasian representatives of the species Paeonia(Punina, 1989) was shown, that at the explored species generally the quantity is slight at heterochromatine, and his distribution similar. Consequently the changes of the chromosomes in the species have come Paeonia in the result of chromosomes -reconstructions into existence. For this reason an interest in the research of the dependence on volumes and DNA - capacity of the chromosomes exists.

Material and method

For the making cytological preparations were used rootspitzen of fully-grown plants, which were cultivated in the experimental section of the botanical of institute of the Russian academy of the sciences, Saint Peterburg,

Materialproben were taken in May and Octobers and in Acetyl - liquor (3:1) fixes. Because it was not possible, to accomplish all Fixationen without exception simultaneous, several series were accomplished, at which respectively the roots of P.caucasica(from Saguramo) were used as standard. At the inquiry of the DNA - capacity this standard was set as 100%. The preparations were colored with Fjolgren. At all series the preparations of a cold hydrolysis were subjected. The staining of all patterns resulted simultaneously, because the intensity is influenced the Kernfärbung of the Fjolgren - reaction through different elements (Brodski, 1960; Marshak et al., 1970). At P.caucasica was produced also a hydrolysis - curve (picture 1).

To the hydrolysis 5n was used HCl at room temperature, with it the Konzentrationsverhältnis and the temperature of the acid a minimal loss of DNA yields (Vahs, 1973; Magakjan, 1980). The optimal Hydrolysezeit was determined with this curve, she/it totals 1h. P.caucasica of different Naturstandorten were determined equal DNA - capacities. The measurement of the DNA - capacity was scanned with a microscope - Photometer of the firm <Opton> and a computer <Wang-720> under application of the software <Itog> and <Statistika>. In the stage the Prophase became a planapo - ++ chromatisches lens 100x/1.3 MI, a Messsonde 0.6mm with a Skalierung in steps of 0.5 mm (550nm) uses. The area of the registered capacity totaled from 87-90 to 1%, around the possibility of cytoplasmatischen pollutions auszuschliessen.

Results and discussion

The results of the determinations of the DNA - capacity shows

If one sets the measured values after P.caucasica eicht and the values determined for P.caucasica the DNA - ++ capacity as 100%, one receives following values:

Tab.3 of relatives DNA - capacity (P.caucasica = 100%)

Species2n%Species2n%P.caucasica (Saguramo)10100 P.lagodechiana 1075.0 - 87.7 P.caucasica (Daba)1097.6 - 100.7 P.steveniana 20175.0 - 187.4 P.mlokosewitschi 10105.1 - 110.0 P.macrophylla 20184.3 - 188.3 P.ruprechtiana 1095.3 - 108.5 P.wittmanniana 20172.3 - 194.3 P.tenuifolia 1048.2 - 72.6 P.tomentosa 20158.1 - 171.5 P.daurica 1073.9 - 81.2 P.officinalis 20162.7

If one puts the dependence between the Gesamtvolumen of the chromosomes and the DNA - capacity in relation to P.caucasica graphically there (picture 2), can see one, that at the diploid species exists a direct non-linear dependence between these parameters, it however simultaneously at the tetraploids a such dependence does not give. There exist many literatur sources, in which the connection between the parameters was explored the karyotype (chromosome number, total chromosome volume, total chromosome length) and the DNA - capacity of the kernel at higher plants. It was demonstrated, that at the most taxons of the plants a direct correlation between the Gesamtvolumen exists the metaphasic chromosomes (or the total footage) and the DNA - capacity (Rees et al., 1966; Rees, Jones, 1972; Price, 1976). This was shown at different species of different species 1 - ++ and 2-keimblättriger flowering plants: Allium (Liliaceae) (Jones, Rees, 1968; Vakhtina et al., 1977), Scilla (Liliaceae) (Greilhuber, 1977, 1979), Bulnesia(Zygophyllaceae) (Poggio et al., 1986), Vicia(Fabaceae) (Chooi, 1977), Lathyrus(Fabaceae) (Narayan, Durrant, 1983), different species of the family Ranunculaceae (Rothfels et al., 1966; Smith, Bennett, 1975); different species of the family Asteraceae: Chrysanthemum(Dowrick, El-Bayoumi, 1969), Anthemidia(Nagl, Ehrendorfer, 1974),Microceris(Price, Bachmanner, 1975),Crepis (Jones, Brown, 1976), Pinus(Dhillon, 1976).

Presently is still uncertain, whether the dependence has a linear or other character. Some authors put a linear (Jones, Rees, 1968; Nagl, Ehrendorfer, 1974; Greilhuber, 1977) dependence between the masses of the chromosomes and the DNA - capacity firmly, others mean, that this dependence has a more complicated character and exponentiell is (Rothfels et al., 1966; Vakhtina et al., 1977).

Repeatedly the question over correlations between DNA - capacity and evolutionary stage of development was put the Taxonome (El-Lakany, Dugle, 1972; Price, 1976; Bennett, Smith, 1976).

The statements are contradictory and newer contradictions exist therein, that between large Taxonomen (in higher families) a very large deviation was observed in the DNA - capacity, which is not dependent from the evolutionary position the Taxon. It exists a tendency to the decline of the DNA - capacity during the specialization of species, for example at the passage of several years ofs to the evolutionary more advanced one-year, like which at several representatives the Asteraceae(Nagl, Ehrendorfer, 1974; Jones, Browii, 1976), the section Cracca of the species Vicia (Chooi, 1971) and the species Ranunculus(Smith, Bennett,1975) was shown.

In the species Paeonia has the legality of the reduction of the DNA - capacity confirmed in the course of the specialization of the species: Them in all morphologicaln features the most extensive developed and specialized P.tenuifolia owns the smallest chromosomes and the least DNA - capacity, P.mlokosewitschi against it, with the least specialization under the diploid Caucasian peonies, owns several large chromosomes and the maximum DNA-content.

What caused the reduction of the DNA - capacity at the diploid peonies? It is known, that a change go can the karyotypes and the DNA - capacity off as result of a change the chromosome number (Anei-ploidie), or as result of chromosomes - reconstructions, how for example at the species Crepis (Asteraceae) (Jones, Brown, 1976), and Bulnesia (Zygophyllaceae) (Poggio et al., 1986), or in result of changes of the correlation of Hetero - ++ to Euchromatin, as at Scilla (Greilhuber, 1979). There are however, how already formerly was shown, (Punina, 1987, 1989), at the representatives of the species Paeonia neither a Anei-ploidie been observed, nor distinctive chromosomes reconstructions, nor essential From species to species the length and thickness of the chromosomes change only. One can proceed on the assumption, that that as result of changes of the increase of the compression was caused, as that for example at the species Vicia(wolves, Martin, 1968), anemone(Rothfels et al., 1966) and Pinus(Dhillon, 1980) was shown.

Together with this question is the DNA - capacity at hybrids between different species interesting, whether their DNA - capacity of their parent species differs. Logically it would be to be assumed, that these hybrids display a medium value in the DNA - capacity, as that e.g. at Chrysanthemumsegetum x Ch.coronarium(Dowrick, El-Bayoumi, 1969) was shown.

At hybrids of the species Microceris presents itself the situation differently: The DNA - capacity the F1 was not in the median value and corresponded to at each reciprocal crossing the capacity the DNA a Mutterart (Price et al., 1985).

In the species Paeonia is the species P.lagodechiana of more hybrid origin, with P.mlokosewitschi and P.caucasica than parent species. That was shown experimentally (Kakheladse, 1965; Kemularia-Nathadse, 1980). The measurement of the thickness of the chromosomes produced surprising results. How already mentions, the thickness of the chromosomes of P.mlokosewitschi 1.64 totaled, which from P.caucasica 1.37mm.

It would be to be assumed been, that the Chromosomendicke of the hybrid species lies either in the means between these both values, or the thickness an of the parents corresponds to. The thickness totaled however at P.lagodechiana only 1.24mm, was still smaller therefore, than which from P.caucasica.

M.S.Navashin (Navashin, 1934) explored in detail the experimentally produced hybrids of the species Crepis. From him/it was noticed a disappearance of satellites, likewise a shortening of all chromosomes of a species in the Cytoplasma the hybrid and simultaneously a disappearance of the differences in the thickness of the chromosomes at the hybrids. For these phenomena he/it stamped the term <Amphiplastie>, whereby he/it a differentielle (the only individual chromosome touches, z.B through the disappearance of satellites) and a neutral (changes of the length and thickness of all chromosomes of a species) Amphiplastie distinguished. It offers itself us, to go out also at the hybrid species of the species Paeonia from a Amphiplastie, which expresses self in changes of the length of the chromosomes the respective Elternart, which itself in the Nivellierung of the differences between the chromosome pair shows (Punina, 1987). A change of the thickness of the chromosomes can have come similarly into existence, which one can interpret likewise as Amphiplastie.

At the investigation of the DNA - capacity of P.lagodechiana showed itself, that he/it is lower, as at the respective parent species. Possibly, that that with it is to be explained, that P.lagodechiana is evolutionary higher developed, as which parent species. In this sense is the appearance a neutral Amphiplastie at the existing object explicable through reduction of the extent of the compression of the chromosomes. Alone this question requires further more special investigations of the different hybrids and hybrid species of the different systematic groups.

At the investigation of the DNA - capacity of P.ruprechtiana we expected, that he/it be must larger than it by P.caucasica in the mass, as the summed up chromosome volume was larger around 30%, than which summed up chromosome volume of P.caucasica were not to be distinguished. However in the DNA - capacity these practically. morphologic differ these both species only little: At P.ruprechtiana are the leaves somewhat broader, than at P.caucasica, are sometimes almost rhombus-shaped, oberseits gleaming, without wax layer (at P.caucasica are the leaves oberseits dull with and/or without Wachsschicht).

At the investigation of the S - segments of the chromosomes of this species (Punina, 1989) no differences could be ascertained, which would have been sufficient, to emphasize P.ruprechtiana as independent species. Therefore we emphasize, that P.ruprechtiana is to be examined only as variant of P.caucasica; the differences in the length and thickness of the chromosomes can be caused through a different degree the Spiralisation of the chromosomes and, consequently, a different compactness the Chromatins at the mitotic chromosomes be caused.

At the investigation of the DNA - capacity the tetraploids species of the species Paeonia could discover we no dependence between the total chromosome volume and the DNA - capacity. One can ascertain solely, that the DNA is so large - ++ capacity the tetraploids species in comparison with the diploid species about doubly, what agrees with the double chromosome volume the tetraploids compared with that the diploid. Consequently, there is at the tetraploids species of the species Paeonia no decrease of the DNA - capacity in the Genom.

At representatives of other systematic groups the polyploidisation both ganzzahlige as well as nichtganzzahlige were observed in the course multiplication of the DNA - capacity. So observed Bennett, Smith (1971) at polyploiden species of the species Hordeum and That (1977) at the triploiden species Puschkinialibanotica a ganzzahlige multiplication of the DNA - capacity during the polyploidisation, i.e. the DNA - capacity the Genoms remained constant.

At experimental Polyploiden ganzzahlige emerge only at low polyploidisation level level multiplication of the DNA - capacity, at higher level the Ploidie observes one a strong refuse of the DNA - capacity in the Genom. That became demonstrates at Viciafaba(Deka, Sen, 1973), Morus and Pink (Akhundova, 1974). Also in the nature appears a reduction the DNA - ++ capacity in the Genom, e.g. to show at species of the species Betula(Grant, 1969) and Festuca(Seal, 1983). Therefore would be it necessary, what the determining elements for the retention of the DNA - capacity are the Genoms at the tetraploids peonies - their taxonomic position or their low polyploidy level (4x).

Which the absolute mass of the chromosomes affects the tetraploids peonies in comparison with the diploid species, so does not occur generally a change of length and thickness of the chromosomes at the polyploidisation, although isolated a reduction can be demonstrated. At other taxons became at the polyploidisation both a reduction of the mass of the chromosomes (Ichicawa et al., 1971; Sharma, 1972), as well as their Constance (That, 1977) shown.

At the species Chrysanthemum(Dowrick, El-Bayoumi, 1976) were observed at different species at the increase the ploidy level both reduced, as well as constant Chromosomenmasse. One believes, that the mass of the chromosomes decrease, if the chromosomes the diploid Ausgangsarten an important capacity at heterochromatic own segments, and conversely, if the Ausgangsarten own little heterochromatine, the mass of the chromosomes do not change at the polyploidisation. If that so is, one can examine finally the observed Constance of the mass the tetraploids as Indiz for it, that a slight quantity is available at heterochromatine.