Effect of separate radioactive and chemical pollutants on the yield of cytogenetic disruptions in the intercalary meristem in spring barley

Dependencies of the yield of cytogenetic disturbances within intercalary meristem cells of spring barley on the soil level of 137Cs (1.48-14.8 MBq/m2), Cd, Pb (2-50 and 30-300 mg per kilogram of the soil) and 2.4-D herbicide (1 or 2 kg/ha) had a non-linear character in the studied range. At low concentrations the yield of cytogenetic disturbances grew faster than at higher ones. Concentrations of lead in soil (at the level of maximum concentration limit) and doses of 2.4-D recommended for agricultural use resulted in the increase in the rate of aberrant cells. The observed rate of cytogenetic disturbances was comparable with the effect of the maximum studied level or the radioactive soil pollution. The heaviest damage to aberrant cells was found in the presence of 137Cs.     

Bio-monitoring the genotoxicity of populations of Scots pine in the vicinity of a radioactive waste storage facility

Results of a long-term (1997-2002) study of the Scots pine populations growing in the vicinity of the radioactive waste storage facility ('Radon' LWPE) are presented. Cytogenetic disturbances in reproductive (seeds) and vegetative (needles) tissues sampled from Scots pine populations were studied to examine whether Scots pine trees have experienced environmental stress in areas with relatively low levels of pollution. The data clearly indicate the presence of mutagenic contaminants in the environment of the pine trees. An increased number of mitotic abnormalities, especially multipolar mitoses was found in the pine tree populations submitted to man-made exposure, which suggests that the cytogenetic damage is mainly caused by chemical contamination. A higher radioresistance of the Scots pine seeds from the impacted populations was shown by use of acute gamma-irradiation. During the observation period 1997-2002, pine trees exposed to anthropogenic pollution showed a steady increase of cytogenetic alterations in the root meristem cells.     

Effect of combined radioactive and chemical (heavy metals,herbicides) pollution on the yield of cytogenetic disruptions in the intercalary meristem of spring barley

The yield of aberrant cells and their loading with lesions of intercalary meristem of spring barley in conditions of the combined action of 137Cs, heavy metals and 2.4-D herbicide was studied. At simultaneous insertion of 137Cs and Cd into the soil, the type of non-linearity of the yield of aberrant cells was determined by radioactive pollution: in a range of low concentrations the synergistic effects took place, in a range of higher ones the antagonistic effects did. In the presence of cadmium, the severity of radiation induced damage to aberrant cells was significantly less. The interaction in 137Cs-Pb pair had an antagonistic character. The yield of aberrant cells was determined mainly by lead, whereas the radioactive pollution played the main role in loading of the aberrant cells with lesions. At the combined pollution with 137Cs and other contaminants, the antagonistic effects were more pronounced with Pb than with Cd, and further increased with the herbicide, both in the test on frequency of aberrant cells and the test on the loading of aberrant cells with lesions. In case of combination of the chemical agents the non-linear effects in test on loading of aberrant cells with lesions were mainly synergistic, whereas in the test on frequency of aberrant cells they were antagonistic. Only Pb-Cd pair and only in the test on loading of aberrant cells with lesions no significant non-linear effects were found. The results show high rate of the induction of synergistic and antagonistic effects in conditions of the combined action of low concentrations of the investigated agents on plants. These effects substantially determined the yield of cytogenetic disturbances in the studied range.     

Cytogenetic effect of low dose γ-radiation in Hordeum vulgare seedlings: non-linear dose–effect relationship

The induction of chromosome aberrations in Hordeum vulgare germinated seeds was studied after ionizing irradiation with doses in the range of 10–1,000 mGy. The relationship between the frequency of aberrant cells and the absorbed dose was found to be nonlinear. A dose-independent plateau in the dose range from about 50 to 500 mGy was observed, where the level of cytogenetic damage was significantly different from the spontaneous level. The comparison of the goodness of the experimental data fitting with mathematical models of different complexity, using the most common quantitative criteria, demonstrated the advantage of a piecewise linear model over linear and polynomial models in approximating the frequency of cytogenetical disturbances. The results of the study support the hypothesis of indirect mechanisms of mutagenesis induced by low doses. Fundamental and applied implications of these findings are discussed. An erratum to this article can be found at     

Mixed chloride–phosphine complexes of the dirhenium core: 9. The first mixed monodentate phosphine complex, 1,2,7,8-Re2Cl4(PMe2Ph)3(PEt2H)

The reduction of the Re₂ ⁵⁺ core in 1,2,7-Re₂Cl₅(PR₃)₃ molecules, followed by addition of 1 equiv. of a different phosphine ligand, PR₃ ′, allows the preparation of the mixed monodentate phosphine compounds of the Re₂ ⁴⁺ type, namely 1,2,7,8-Re₂Cl₄(PR₃)₃(PR₃ ′). The stereochemistry of the starting materials dictates the stereochemistry of the final products. The one-electron reduction of the 1,2,7-isomer of Re₂Cl₅(PMe₂Ph)₃ with KC₈ to the corresponding anion, [1,2,7-Re₂Cl₅(PMe₂Ph)₃]⁻ (1), followed by non-redox substitution of one chloride ion by one diethylphosphine, PEt₂H, afforded the first mixed monodentate phosphine compound of the dirhenium(II) core, Re₂Cl₄(PMe₂Ph)₃(PEt₂H) (2), in good yield. Crystal structure determination as well as other physical methods and elemental analysis unambiguously confirmed the formation of 2. The related system 1,2,7-Re₂Cl₅(PMe₃)₃---Co(C₅H₅)₂---PEt₂H leads to several products, one of which is 1,2,7,8-Re₂Cl₄(PMe₃)₃(PEt₂H) (3).     

Genetic variability in Scotch pine populations of the Bryansk Region radioactively contaminated in the Chernobyl accident

The method of isozyme analysis of megagametophytes is used to estimate the genetic variability in Scotch pine populations (Pinus sylvestris L.) of the Bryansk Region sites with contrasting levels of radioactive contamination (soil ¹³⁷Cs, 60 to 17 800 Bq/kg) resulting from the Chernobyl accident. All indices of genetic variability (heterozygosity, frequency of polymorphic loci, Zhivotovskii index) and frequencies of loss-of-function enzyme mutations increase with the dose absorbed by plant generative organs. The data show that high mutability is intrinsic for seeds of these pine trees, and genetic diversity in the populations is essentially conditioned by radiation exposure.     

Biological effects of chronic radiation exposure on plant populations

The findings from long-term field studies on biological effects in plant populations inhabiting radioactively contaminated territories contrast in levels and compositions of dose-forming radionuclides are presented. Plant populations developing under radioactive impact show enhanced frequencies of gene and chromosome mutations, and their reproductive potential is inferior to reference populations. Even relatively low levels of technogenic impact are able to increase genetic diversity and destroy regularities inherent for intact populations. Chronic radiation exposure from a certain level appears to be an ecological factor changing genetic structure of wild populations. Data presented indicate the presence of adaptation processes in plant populations in territories with technogenic impact. Under ecological stress, there are selection processes for resistance improvement in plant populations. But an appearance and rate of this process can essentially differ in dependence on radioecological conditions.