Chromosome numbers in 11 species of Taraxacum section Erythrosperma dt. from Poland

Karyology of eleven species of Taraxacum sect. Erythrosperma from Poland has been studied. Somatic chromosome numbers are given for the following species: T. bellicum, T. brachyglossum, T. cristatum, T. disseminatum, T. dissimile, T. lacistophyllum, T. parnassicum, T. plumbeum, T. proximum, T. scanicum, and T. tenuilobum. Although the hypertriploid chromosome number was previously reported in Poland for T. lacistophyllum, T. parnassicum, T. scanicum, and T. tenuilobum, we proved the triploid chromosome number 2n = 24 in all the species investigated, which is consistent with the data reported from other regions of Europe. The chromosome numbers of T. bellicum, T. cristatum, T. disseminatum, T. dissimile, T. plumbeum, and T. proximum growing in Poland are published for the first time

Chromosome numbers in Hieracium (Asteraceae) from Central and Southeastern Europe I

Chromosome numbers for 16 Hieracium s.str. species from Bosnia and Herzegovina, Bulgaria, Macedonia, Montenegro, Poland, Romania and Serbia are given and their metaphase plates are illustrated. Chromosome numbers are published for the first time for H. filarszkyi Jáv. & Zahn 2n = 3x = 27, H. fritschianum Hayek & Zahn 2n = 3x = 27, H. fritzeiforme Zahn 2n = 3x = 27, H. hercegovinicum (Freyn & Vandas) Szeląg 2n=3x=27, H. nivimontis (Oborny & Zahn) Chrtek fil. 2n = 4x = 36, H. vagneri Pax 2n = 4x = 36, as well as three undescribed species of hybrid origin between H. olympicum Boiss. and H. sparsum Friv. 2n = 4x = 36, H. naegelianum Panč. and H. scardicum Bornm. & Zahn 2n = 3x = 27, and H. transylvanicum Heuff. and H. umbellatum L. 2n = 4x = 36

Chromosome numbers in Hieracium (Asteraceae) from Central and Southeastern Europe V

Chromosome numbers for 15 taxa of Hieracium s.lat. (including two taxa of Pilosella Vaill.) from Bosnia and Herzegovina, Bulgaria, Greece, North Macedonia, Poland, Romania and Slovakia are given and their metaphase plates are illustrated. Chromosome numbers are published for the first time for H. pannosum subsp. parnassi Nägeli & Peter from Greece (3x and 4x), and for an undescribed species of H. sect. cernua from North Macedonia (4x). a new, diploid chromosome number was found in H. bracteolatum s.lat. from Greece

Pattern of callose deposition during the course of meiotic diplospory in Chondrilla juncea (Asteraceae, Cichorioideae)

Total absence of callose in the ovules of diplosporous species has been previously suggested. This paper is the first description of callose events in the ovules of Chondrilla juncea, which exhibits meiotic diplospory of the Taraxacum type. We found the presence of callose in the megasporocyte wall and stated that the pattern of callose deposition is dynamically changing during megasporogenesis. At the premeiotic stage, no callose was observed in the ovules. Callose appeared at the micropylar pole of the cell entering prophase of the first meioticdivision restitution but did not surround the megasporocyte. After the formation of a restitution nucleus, a conspicuous callose micropylar cap and dispersed deposits of callose were detected in the megasporocyte wall. During the formation of a diplodyad, the micropylar callose cap decreased and the walls of a newly formed megaspores showed scattered distribution of callose. Within the older diplodyad, callose was mainly accumulated in the wall between megaspores, as well as in the wall of the micropylar cell; however, a dotted fluorescence of callose was also visible in the wall of the chalazal megaspore. Gradual degradation of callose in the wall of the chalazal cell and intense callose accumulation in the wall of the micropylar cell were related to the selection of the functional megaspore. Thus, our findings may suggest that callose fulfills a similar role both during megasporogenesis in sexual angiosperms and in the course of meiotic diplospory in apomicts and seems to form a regulatory interface between reproductive and somatic cells

Ovules anatomy of selected apomictic taxa from Asteraceae family

The present paper reports on our observations on the ovule structure of autonomous obligatory apomicts. We analyzed two triploid species of Taraxacum: T. udum, T. alatum and two triploid species of Chondrilla: Ch. juncea, Ch. brevirostris. The ovules of all studied species show a structure typical for the members of Asteraceae. One basal ovule develops into an inferior and unilocular ovary. The ovule is anatropous, tenuinucellate and unitegmic. Structural changes were observed in the ovule at the time of the embryo sac maturation. The innermost layer of integument develops into an endothelium surrounding the female gametophyte. Moreover, considerable modifications occurred in the integumentary cell layers adjacent to the endothelium. These cells show signs of programmed cell death and their walls begin to thicken. Histological analysis revealed that the prominent thick cell walls were rich in pectins. Layers of thick-walled cells formed a special storage tissue which, most likely, is an additional source of nutrients necessary for the proper nourishment of a female gametophyte and then of a proembryo

Egg apparatus in sexual and apomictic species of Taraxacum : structural and immunocytochemical aspects of synergid cells

The paper reports a comparative study of the female gametophyte and especially synergid structure in sexual and apomictic dandelions. We analyzed diploid sexually reproducing Taraxacum linearisquameum (2n = 2x = 16) and two triploids, T. alatum and T. udum (2n = 3x =24), with autonomous embryo and endosperm development. There were no observed differences in the organization of the mature megagametophyte between the examined species. Both meiotically reduced and diplosporous embryo sacs showed typical polarity of the egg apparatus cells, together with development of a filiform apparatus in the synergids, but immunocytochemical analyses indicated that microtubules form longitudinal brush-like bundles adjacent to the filiform apparatus in the synergids of the sexual T. linearisquameum. This arrangement of cytoskeletal elements is similar to the configuration described in other amphimictic plants. The synergids of the apomictic T. alatum and T. udum show a uncharacteristic and relatively weak cytoskeleton with no brush-like bundles. We discuss the role of synergids in autonomous apomicts

Chromosome numbers in Hieracium (Asteraceae) from Central and Southeastern Europe III

Chromosome numbers for 13 species of Hieracium L. s.str. from Bulgaria, Macedonia, Poland and Romania are given and their metaphase plates are illustrated. Chromosome numbers are published for the first time for H. djimilense s.lat. 2n=3x=27, H. fiekii R. Uechtr. 2n=3x=27, H. glabrescens (F. W. Schultz) Murr 2n=3x=27, H. juranomorphum Zahn 2n=3x=27, H. sparsiflorum subsp. sparsiceps Zahn 2n=3x=27 and H. sparsum subsp. naegelianiforme Behr & Zahn 2n=3x=27

FISH-aimed karyotype analysis in Aconitum subgen : aconitum reveals excessive rDNA sites in tetraploid taxa

The location of 5S and 35S rDNA sequences in chromosomes of four Aconitum subsp. Aconitum species was analyzed after fluorescence in situ hybridization (FISH). Both in diploids (2n = 2x = 16; Aconitum variegatum, A. degenii) and tetraploids (2n = 4× = 32; A. firmum, A. plicatum), rDNA repeats were localized exclusively on the shorter arms of chromosomes, in subterminal or pericentromeric sites. All analyzed species showed similar basal genome size (Cx = 5.31-5.71 pg). The most striking features of tetraploid karyotypes were the conservation of diploid rDNA loci and emergence of many additional 5S rDNA clusters. Chromosomal distribution of excessive ribosomal sites suggests their role in the secondary diploidization of tetraploid karyotypes