7-day soil drought followed by 7-day rehydration was applied to potted German chamomile (Chamomilla recutita) plants at the beginning of their generative stage. Plants of a wild type (WT), plus two diploid (2n) and two tetraploid (4n) genotypes were studied, in order to examine the alterations in chlorophyll (Chl) and carotenoids (Car) contents, and chlorophyll fluorescence (CF) parameters during water shortage and rehydration. The fresh mass of the anthodia after the recovery was also studied.
WT plants adjust better to water stress than modern breeding genotypes, because drought resulted in the low fall in leaf water content of WT, the lowest decrease in the fresh mass of its anthodia (a 41% decrease from the control), and the most elastic response of the photosynthetic apparatus. 4n C11/2 strain plants suffered from the highest reduction in anthodia yield (87%), and had the lowest constitutive pigment contents. It was also the only genotype which revealed nontypical alterations in various CF parameters obtained on a dark- and light-adapted leaf. During drought, a big increase was noticed in minimal, maximal, and variable fluorescence of PSII reaction centres in the dark- adapted (F0, Fm and Fv, respectively), and in the light-adapted state (F0', Fm' and Fv')., It was accompanied by the biggest decline in linear electron transport rate (ETR), quantum efficiency of PSII electron transport (ΦPSII) and photochemical quenching coefficient (qP). These alterations were prolonged to the stage when the normal leaf water content was retained. On the contrary, C6/2 strain plants had the highest constitutive Chl and Car contents, which additionally increased after rehydration, similarly to the values of F0, Fm and Fv, which reflects the high photosynthetic potential of this genotype. It was accompanied by the relatively high yield of its anthodia after drought. Considering the drop in the yield triggered by drought, it seems to be the only parameter which may be linked with the ploidy level.
Although the yield formation of chamomile strains cannot simply be estimated by CF assay, this technique may serve as an additional tool in the selection of plants to drought. The following circumstances should be submitted; namely: measurement at the proper developmental stage of plants, in different water regimes, and an analysis of various CF parameters. The increase in F0 and F0', and the reduction in ETR, Fv'/Fm', ΦPSII and qP values in response to water deficit should be an indicator of the impairment of the photosynthetic apparatus through drought., and R. Bączek-Kwinta ... [et al.].
The molecular karyotype of Paranosema grylli Sokolova, Seleznev, Dolgikh et Issi, 1994, a monomorphic diplokaryotic microsporidium, comprises numerous bright and faint bands of nonstoichiometric staining intensity. Restriction analysis of chromosomal DNAs by ''karyotype and restriction display'' 2-D PFGE has demonstrated that the complexity of molecular karyotype of P. grylli is related to the pronounced length polymorphism of homologous chromosomes. The background of this phenomenon is discussed in the context of ploidy state, reproductive strategy and population structure in this microsporidium. We propose that the remarkable size variation between homologous chromosomes in P. grylli may be a consequence of ectopic recombination at the chromosome extremities.
Despite the substantial knowledge of the variation in cytotypes at large spatial scales for many plants, little is known about the rates at which novel cytotypes arise or the frequencies and distributions of cytotypes at local spatial scales. The frequency distribution, local spatial structure, and role of habitat differentiation of tetra-, penta- and hexaploid cytotypes of the bulbous geophyte Allium oleraceum were assessed in 21 populations sampled in the Czech Republic. The ploidy levels determined by flow cytometry confirmed that there was a mixture consisting of two or three cytotypes (i.e. 4x+5x, 4x+6x, 5x+6x, 4x+5x+6x). In addition, mixtures of cytotypes were found at sites previously considered to be cytotype-homogeneous. At all sites previously found to contain a mixture of two cytotypes, no plants with the third ploidy level were found. Although the relative frequencies of cytotypes varied considerably both among and within populations, mixed populations consisting of tetra- and hexaploids were usually dominated by tetraploids. This suggests that there are secondary contacts among cytotypes but there is little gene flow among them except for the rare formation of hexaploids in tetraploid populations. Cytotypes were not randomly distributed over the study area but were spatially segregated at either 47.6% or 61.9% of the sites investigated, depending on the statistical test (Mantel test or average distance test) used. When the composition of habitats at each of the sites is taken into account, cytotypes were more frequently spatially segregated at sites with a heterogeneous environment than a homogeneous environment. This implies that the cytotypes are ecologically differentiated. The frequent co-occurrence of cytotypes, with or without significant spatial segregation, at many sites with heterogeneous or homogeneous environments, however, suggests that niche differentiation alone is probably ineffective in determining co-occurrence. It is supposed that the prevailing vegetative reproduction associated with local dispersal, a high population density of the species in a landscape, and non-equilibrial processes influencing the establishment and extinction of A. oleraceum populations can also support the local co-occurrence of cytotypes.
The formation and maintenance of polyploids (via the development of various reproductive barriers) rank among the central questions of studies on polyploid evolution. However, the long time scale of most evolutionary processes makes the study of the dynamics of diploid-polyploid groups difficult. A suitable candidate for a targeted comparative study is Vicia cracca (Fabaceae), which in the late 1960s was subjected to a detailed cytotype screening in Central Europe. Re-sampling the original localities offers a unique opportunity to assess changes in the ploidy structure of the populations, which should reflect the cumulative effect of all the evolutionary forces acting on the plants. Using flow cytometry, the DNA ploidy levels of more than 6,500 individuals of V. cracca collected at 257 localities in Austria, the Czech Republic, Germany and the Slovak Republic were estimated. Three different cytotypes (2x, 3x and 4x) were detected. While tetraploids predominated in the western part of the area investigated (179 populations), the diploids had a more easterly distribution (62 populations). There is a secondary zone of cytotype contact near the boundary between the Czech and Slovak Republics. Sixteen populations (~6%) consisted of a mixture of 2x and 4x cytotypes. Triploids are very rare; only seven individuals were found in two otherwise diploid populations, indicating the existence of breeding barriers between diploids and tetraploids. The distribution of cytotypes is similar to that determined four decades ago using chromosome counts. Nevertheless, there are some discrepancies, namely the current absence of: (i) the diploid cytotype in southern Bohemia and (ii) the altitudinal segregation in the distribution of cytotypes, including two formerly recognized chromosomal races of diploids, perhaps a result of more representative sampling. Identical monoploid genome sizes (1Cx-values) of both the majority ploidy levels support an autopolyploid origin of the tetraploids.
DAPI and propidium iodide flow cytometry were used to determine the variation in genome size in 166 samples and of all taxa and ploidy levels of Fallopia section Reynoutria (knotweeds) recorded in the Czech Republic. Significant differences were detected in the amount of nuclear DNA, associated with the ploidy levels and taxonomic identity of the material. At each ploidy level, F. sachalinensis showed the lowest and F. japonica the highest fluorescence intensities. The fluorescence values for the hybridogenous F. ×bohemica were located in-between these two levels. In most cases, there was at least a four-percent gap in fluorescence values between the nearest neighbours belonging to a different taxon. Intraspecific variation in genome size was very low in all taxa except hexaploid F. ×bohemica; this could be due to the complex evolutionary history of this taxon. Our results indicate that the amount of nuclear DNA can be used as a reliable marker for the identification of homoploid knotweed species and their hybrids. Different evolutionary pathways for the origin of high polyploids and/or hybridogenous taxa are proposed based on genome size.
Wheat provides a unique genetic system in which variable sink size is available across the ploidies. We characterized monocarpic senescence in diploid, tetraploid, and hexaploid wheat species in flag leaf from anthesis up to full grain maturity at regular intervals. Triticum tauschii Acc. cv. EC-331751 showed the fastest rate of senescence among the species studied and the rate of loss per day was highest in terms of photosynthesis rate, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) content, and flag leaf N content coupled with a higher rate of gain in grain N content. Cultivars Kundan and HD 4530 maintained high flag leaf N content throughout grain filling as compared to the diploids and showed a slower rate of senescence. RuBPCO content was higher in the diploids as compared to Kundan and HD 4530 at anthesis. However, the rate of decline in RuBPCO content per day was also higher in the diploids. This degradation in RuBPCO was mediated by high endoproteolytic activities in the diploids which in turn supported its higher rate of N mobilization as compared to the tetraploid and hexaploid wheat. Acidic endopeptidases were responsible for the mobilization of flag leaf nitrogen in wheat across ploidy levels (r=-0.582, p<0.01). and B. Srivalli, R. Khanna-Chopra.