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The study was undertaken to study a relationship between the changes of some parameters of the biochemical and mineral composition of different plants, such as rape, pods, and lentil, and the levels of soil radiation pollution, by using the conventional methods. Radioactive pollution of dark-grey forest soils was found to cause a change in the biochemical composition of plant seeds even at the level of cesium 137 (137Cs) within the present temporary permissible levels (TPL) (600 Bq/kg): there were elevated concentrations of salts of potassium, phosphorus, ammonia nitrogen, catechols, sucrose, and some amino acids. With the radioactive cesium level exceeding the TPL, biochemical changes in the seeds depended on the species of the plants: in the rape seeds, the additional formation of sucrose and amino acids continued, but less intensively than with its lower radiation; the pod beans were significantly positively correlated with the increasing amounts of catechols.

Dose rates cause no adverse effects on natural populations of Pinus sylvestris L. and Vicia cracca L. inhabiting territories contaminated by uranium mill tailings and radium production wastes (Vodny settlement, Komi Republic) were determined. A significant increase in embryonic lethal mutation frequency in V. cracca legumes and decrease in seedlings survival rate as compared with control values were registered at dose rate equal to 1.67 mGy/day, that is 280 times higher than the one calculated for the reference site. The adverse effects in P. sylvestris expressed in increased frequency of chromosome aberrations in meristematic root tips and decreased reproductive capacity of seeds were determined at absorbed dose rate equal to 0.083 mGy/day. Data obtained show that the decrease in plant reproductive capacity in case of chronic exposure of radionuclides of uranium and thorium decay series can observe at lower weighted absorbed dose rates than in case of environmental contamination by artificial radionuclides.

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.

The spontaneous level of cytogenetic damage in three plant species (Achyrophorus maculatus (Scop.) L., Plantago lanceolata L., Plantago media L.) growing at the territory of East Ural radioactive trace was studied. The radiation resistance of plants from radioactive and control nonpolluted sites was determined. The effects of additional fractionated irradiation by different doses and the role of antioxidant systems in the formation of radioprotector effect were examined. It was shown that the level of mutation process in the plant populations growing at the radiation polluted sites is increased compared to the control populations from the pure territory. The additional acute gamma-irradiation of seeds collected from the polluted and pure territories showed the improved radiation resistance of the plants from the polluted territory. In the control population of A. maculatus in the versions with a one-hour interval between fractions, the radiation effect follows the additivity principle; in the same time, at a one-day interval between fractions, a highly significant radioprotective effect manifested most clearly in the experimental population is induced. For higher plants, the enhanced effectiveness of the functioning of antioxidant systems in plants growing at radiation polluted territories was first shown. Thus, the radioprotector mechanisms of low-dose chronic and preliminary irradiation are similar and one of these mechanisms is the activation of antioxidant systems in plants growing under conditions of chronic low-intensity irradiation for long periods of time.

In the Eastern Ural Radioactive Trace, concentrations of 90Sr, the main contaminant, in the upper topsoil was estimated to be 40-17000 times over the global level. The density of contamination decreased with the distance from the accident plot according to exponential law. The resulting doze loads shown an excess over the background level of about 1-3 orders of magnitude. Vegetation in the head part of the EURT is represented with synanthropic and seminatural communities undergoing different phases of degradations and recovery successions. Phytocenosis degradation is caused by the failures during the accident, subsequent reinstatement and restoration activities and also by the initial anthropogenic load. The ecological and genetic effects of permanent ionizing radiation on plants are evident from a wider spectrum of variability for all indicators of the living ability of seed posterity and their increased mutability. The effect of radioadaptation, i.e. increased the resistance to the additional irradiation, in the EURT plants was not found.

Aberrant cell frequency in root meristem of germinated seeds collected from four populations of Scots pine in the Bryansk Region that was radioactively contaminated as a result of the accident at the Chernobyl NPP in 1986 significantly exceeded the control level durring all three years of study (2003-2005). An analysis of cytogenetic disturbances occurrence in dependence on radiation situation characteristics such as 137Cs and 90Sr content in pine cones, 137Cs specific activity in soil, and calculated doses absorbed by pine tree generative organs shows an increase in biological effect with dose burden increasing. Findings obtained are in agreement with the results of our previous studies on cytogenetic effects induction in Scots pine populations experiencing chronic radiation (the 30-km zone of the ChNPP) and technogenic (a radioactive waste reprocessing facility) impact.

Cytogenetic characteristics of the seed progeny of birch (Betula pendula Roth), growing in colony Urazovo Belgorod region exposed by the impact of Chernobyl precipitation in 1986, were determinated. The changing of cytogenetic characteristics in comparison with the control (mitotic index and level of mitosis pathologies grown, their spectrum widens part of persistent nucleolies at the stages of metaphase, anaphase, telophase of mitosis enlarges, square of surface of single nucleolies decreases, part of moderate-active nucleolies "bark-core vacuolisated" type increase) on the experimental squares is revealed. The most considerable effects were observed in 2000, which connected with the increasing of the contaminations of mentioned territory as a result of brick factory work. By means of cluster analysis methods it was established that the cleanest in northwestern part of colony Urazovo, the most contaminated is central part. It was purposed, that chemical compounds, are main agents caused the changing of cytogenetic properties of test-object after the normalization of the radiation level.

The effect of stress factors (small doses of radiation and maximum temperatures in the econiche of the tested plants (tmax)) as well as aging on pea seeds, both acting independently and in combination, is estimated. Here we evaluate the influence of oxidizing stress on pea seeds in the laboratory (gamma-irradiated with 7 cGy at 0.3-19.1 cGy/h, tmax approximately 30-32 degrees C) and on natural plantain seeds collected in a 30-km zone of NPP (radiation exposure approximately 15 R/h, tmax approximately 38-40 degrees C). We have mathematically modeled CAs frequencies in root seedlings meristeme by invoking an enhancing factor transmitted from cell to cell. It is shown under the stress conditions: 1) CA frequency decreases whereas the fraction of inviable seeds (IS) increases, the dependence of IS on CA frequency being inversed; 2) a stimulation of proliferation of cell was observed; 3) a bystander effect appears; 4) antioxidative status (AOS) of seeds influences on adaptation on the all levels of the organization; 5) IS increases up to 73-80% under the combined effect of radiation and heat stresses.

The results of the determination of radionuclide and chemical (multielement analysis) soil pollution are presented. The data on antioxidant status of plantain (Plantago major L.) in conjunction with the data on radionuclide and chemical pollution are analyzed. The most significant decrease in antioxidant activity of plant seeds was observed in areas situated along the most frequent wind direction in the region in summer 1998. It is suggested that lower antioxidant status is caused by the chronic radionuclide release on the chemically polluted territories.

Genetic consequences of a prolonged action of ionizing radiation were analyzed in five natural Crepis tectorum populations growing at the radioactively contaminated territory of the East-Ural radioactive track. In these populations about 40 years after the start of a chronic irradiation an increased frequency of chromosome aberrations was found out. An additional acute gamma irradiation at the dose of 20 Gy did not reveal any changes of radioresistance of the plants investigated.

The generation of seeds of two populations of Viola matutina Klok. sampled from plants growing within the thirty-kilometers zone of the Chernobyl accident (the reproduction of seeds in 1988) was investigated in the north nursery in Syktyvkar. The decrease of sterile pollen and embryonic lethality among the plants from the strongly contaminated site (exposure rate (1075-1434) pC/(kg.s) May 1987) was registered. It is suggested that this phenomenon is the result of the elimination of genetic damages in the course of seed forming in this population under radiation stress.