František Krahulec

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The versatility of the breeding system in the hybridogenous hexaploid, Hieracium rubrum, was demonstrated in emasculation and crossing experiments. The flow-cytometric ploidy analysis of 1095 seedlings amongst its' progeny enabled the determination and quantification of the reproductive pathway (apospory, haploid parthenogenesis, cross-fertilization of both(More)
BACKGROUND AND AIMS Hieracium sub-genus Pilosella (hawkweeds) is a taxonomically complicated group of vascular plants, the structure of which is substantially influenced by frequent interspecific hybridization and polyploidization. Two kinds of species, 'basic' and 'intermediate' (i.e. hybridogenous), are usually recognized. In this study, genome size(More)
Both vertical and horizontal heterogeneity in red light levels and in the red/far red ratio were measured in a mountain grassland and correlated with the vegetation structure. Vertical change in the red/far red ratio was measured in three communities; canopy structure and density was investigated by the point-quadrat method and biomass harvesting.(More)
The closely related species, diploidAnthoxanthum alpinum Á. Löve etD. Löve and tetraploidAnthoxanthum odoratum L., have distinct distributions:A. alpinum is an arctic-alpine species, whileA. odoratum is a species of lower altitudes and more southerly latitudes. However, some authors suggest that both species are potentially able to maintain their(More)
Flow cytometric and karyological investigations were performed on the closely related taxaElytrigia repens andE. intermedia (Poaceae: Triticeae) from the Czech Republic. DNA-hexaploids clearly prevailed among 238 examined plants and amounted to 96.2% of all samples. 2C-values ± s.d. for hexaploidElytrigia repens andE. intermedia were estimated at 23.27 ±(More)
BACKGROUND AND AIMS Natural hybridization was investigated between two predominantly allohexaploid wheatgrasses, weedy Elytrigia repens and steppic E. intermedia, with respect to habitats characterized by different degrees of anthropogenic disturbance. METHODS Using flow cytometry (relative DNA content), 269 plants from three localities were analysed.(More)
Permanent plots with a fine scale recording system were used to trace the spatiotemporal process within two mountain grasslands in the Krkonoše Mts., Czech Republic. The analysis used autocorrelation over increasing lags in space and/or time. Moran'sI was used to measure the autocorrelation. There was a lot of variation between species both in spatial and(More)
We studied the significance of sexual reproduction as a source of ploidy level variation in a model system consisting of hexaploid, facultatively apomictic Pilosella bauhini and tetraploid, sexual P. officinarum. As the maternal parent, apomictic P. bauhini generated higher ploidy level variation than sexual P. officinarum. Ploidy levels of its progeny(More)
BACKGROUND AND AIMS Despite extensive study of polyploidy, its origin, and ecogeographical differences between polyploids and their diploid progenitors, few studies have addressed ploidy-level structure and patterns of ecogeographical differentiation at various spatial scales using detailed sampling procedures. The pattern of coexistence of polyploids in(More)