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Main results of the nineteen year radiation-genetic monitoring of radiobiological, of cytogenetic, and of genetic parameters of Pinus sylvestris L. of forest plantation from the Chernobyl meltdown area are presented. The acute ionizing irradiation at doses >1 Gy induces the formation of morphoses and of depressed growth; at doses >2 Gy, the reproductive ability of the trees declined. The radiobiological parameters shown linear or close to it dose-dependence relationship. The acute irradiation at dose of 0.5 Gy induces cytogenetic and genetic effects that were significantly higher than the corresponding control values. The relationship between the cytogenetic effects and the absorbed dose was exponential. The dependence of mutation frequency at specific loci on the absorbed dose was described by a nonlinear curve. The results of the cytogenetic analysis of seedlings obtained from seeds annually collected in zones of slight, of moderate, and of strong damage of Pinus sylvestris L. are presented.

The main results of the 12-year radiation-genetic monitoring of radiobiological, cytogenetic, and genetic parameters in the Pinus sylvestris L. forest plantations from the zone of the accident at the Chernobyl nuclear power plant presented. Acute ionizing irradiation at doses > 1 Gy was shown to induce the formation of morphoses and depressed growth; at doses > 2 Gy, the reproductive ability of the trees declined. The radiobiological parameters showed a linear (or close to linear) dose-effect relationship. Acute irradiation at a dose of 0.5 Gy induced cytogenetic and genetic effects that were significantly higher than the corresponding control values. The relationship between the cytogenetic effects and the absorbed dose was exponential. The dependence of the mutation frequency at specific loci on the absorbed dose was described by a nonlinear curve. The results of cytogenetic analysis of sprouts obtained from seeds annually (1986-1998) collected in zones of slight, moderate, and strong damage of Pinus sylvestris L. are presented.

Mutation dynamics in generations was studied in natural populations of plants from the East Ural Radioactive Track (EURT, Kyshtym accident). The experiments were aimed at the investigation of the formation of genetic load in natural plant populations under conditions of prolonged radiation exposure. The main approach used in the study was the analysis of cytogenetic alteration, chlorophyll and gene mutations in plants exposed for more than 40 years to chronic beta-irradiation and in their progeny.

The main results of the 12-year radiation-genetic monitoring of radiobiological, cytogenetic, and genetic parameters in Pinus sylvestris forest plantation from the Chernobyl meltdown area are presented. The acute ionizing irradiation at doses > 1 Gy was shown to induce formation of morphoses and depressed growth; at doses > 2 Gy, the reproductive ability of the trees declined. The radiobiological parameters showed a linear or close to linear dose-dependence relationship. The acute irradiation at a dose of 0.5 Gy induced cytogenetic and genetic effects that were significantly higher than the corresponding control values. The relationship between the cytogenetic effects and the absorbed dose was exponential. The dependence of the mutation frequency at specific loci on the absorbed dose was described by a nonlinear curve. The results of cytogenetic analysis of seedlings obtained from seeds annually collected in zones of slight, moderate, and strong damage of Pinus sylvestris L. are presented.

Cytogenetic and genetic effects in populations of Pinus sylvestris L. suffered wiak, average, strong and sublethal radiation damage after the Chernobyl accident in 1986 were studied. The absorbed dozes for trees in these plantings were from 0.1 up to 20 Gy. It was shown that the amount of cells with chromosome aberrations in sprouts of seeds of a crop of 1993, are comparable with effects marked at once after accident in 1986. In 1997 and in 1998 the amount of cells with chromosome aberrations in sprouts of seeds in majority inspected plantings decreased to control values. The effect of adaptation was detected, when seeds of Pinus sylvestris L., gathered in 1997 from inspected trees, were exposed to additional 4 Gy gamma-radiation.

Isoenzyme and morphological polymorphism alteration in populations of perennial grass Centaurea scabiosa L. (scaly cornflower) has been studied. These populations exist on the territory of East Ural Radioactive Trace more than 40 years and are chronically exposed to beta-irradiation. Directional shift of allele frequencies on the loci Per1, Pgi2, Sod1, Lap has been detected. The fact of accumulating genetic load by chronically irradiated populations has been demonstrated. Possible reasons of discovered alterations are discussed. The analysis of the obtained data shows that the irradiated populations have greater similarity with one another than with a control, but relation between genetic distances and accumulated doses hasn't been revealed. The hypothesis is that an extra factor--gene flow from a "clean" territory influences the genetic structure of irradiated populations.

Studies to analyze the genetic processes in natural populations of plants were started on the territory of the East-Ural Radioactive Trace (EURT) in 1962 and in the zone of the Chernobyl accident in May 1986. The main directions of the genetic studies in both radioactive areas were similar: 1) study of the mutation process intensity depending on the dose and dose rate and analysis of dose-effect relationships for different genetic changes (point mutations, chromosome aberrations in mitosis and meiosis) in irradiated plant populations; 2) study of the mutation process dynamics in generations of chronically (prolongly) irradiated populations of plants; 3) analysis of microevolutionary processes in irradiated plant populations. The report presents an analysis of observed dose-effect relationships under the action of radiation on populations of Arabidopsis thaliana, Pinus sylvestris and a number of other plant species. Analysis of the mutation processes dynamics in 8 Arabidopsis populations growing in the zone of the Chernobyl catastrophe has demonstrated that the level of the embryo lethal mutations 10 years after the accident in the irradiated populations significantly exceeds the control level. The following phenomena observed in chronically irradiated populations have also been considered: increased radioresistance of irradiated populations (radioadaptation), the appearance of abnormal karyotypes and selective markers upon chronic irradiation. The authors call attention to the high importance of monitoring of genetic processes in irradiated plant populations for understanding of the action of radiation on human populations.

Populations of Arabidopsis thaliana (L.) Heynh., and Pinus sylvestris L., growing within 30 km of Chernobyl and Bryansk region have been analyzed for the frequency of embryonic lethal mutations on Arabidopsis and frequency of chlorophyll mutations and chromosome aberrations by pine. On pine also have been analyzed rate of mutations at enzyme loci in endosperms of seeds. Dose dependence of the value genetic damage on level of radioactive pollution was observed.

The examination of chronically irradiated natural populations of C. scabiosa L. have been carried out for 30 years at the territory of the east Urals radioactive trial. By using of different tests (frequency of aberrant cells, chlorophyll mutations and mutations in Lap locus) the mutation rates in chronically irradiated populations and in the control natural populations were compared. It was shown that long-term radiation influence caused changes in population genetic structure due to induction of new allelic forms and selection of more adapted genotypes.

The method of isoenzyme electrophoresis was used for comparative evaluation of genetical effects in populations of Pinus sylvestris L. growing in Kyshtym region (east Urals), the Chernobyl accident zone and in the region of Semipalatinsk nuclear tests (Altai). It was shown that mutation frequencies for allozyme loci are ranged as follows: Ural > Altai > Chernobyl.

Segregation of polymorphic diallelic loci, which encode isozyme synthesis in seed endosperms of Pinus Sylvestris L. trees exposed to various levels of radiation after Chernobyl' meltdown, was studied. It was shown that directional gametic selection, expressed as segregation distortion in heterozygotes, is observed in irradiated populations for a number of loci. The detected selection has one-locus character and distinctly influences the gene pool of the next generation.

Mutagenesis of alleles of 20-allozyme loci was studied using the electrophoresis methods in polyacrylamide gel in seeds of Pinus sylvestris within the 30 km zone of the Chernobyl NNP and the limits of contamination levels by Cs-137 from 5 up to 600 Cu/km (the absorbed doses being 0.5 to 10 Gy). The frequency of emergence of corresponding mutations which change the synthesis of enzymes in endosperms within the zone constituted on the average 2.7-10 per gene as compared with 0.6-10 in control version. Linear dependence was observed between low doses absorbed and the frequency of gene mutations, while in case of high doses this decreased. Genetic effectivity was 0.001 mutations/locus/Gy. Various radiosensitivity levels were shown among the loci studied. Spontaneous level of mutations frequency in P. sylvestris populations was found to be within the limits of 0.5 to 1.5 Gy under conditions of the 30 km zone. The high rate of mutagenesis was revealed in seeds of the first two post-accident reproductions.

On the basis of analysis of the literature and personal data, principles of dosimetry were determined and an analysis was given of biological effects of radionuclides on plants when administered aerially and by root. A comparison was made of radiosensitivity of barley and dependence of sensitivity on the growth phase of the plant at the time of irradiation with a standard LD50 and UD50. The possibility of using correlated paramaters of bioinformation, such as the sensitivity indicator of evaluation of biological effects caused by small radiation doses, is considered. On the basis of correlations of the data obtained a prognosis is made of the probability of losses in harvest of grains subjected to radionuclides at various periods of development.