A dose rate causes no fluctuating asymmetry indexes changes in silver birch (Betula pendula (L.) Roth.) leaves and Scots pine (Pinus sylvestris L.) needles in the Chernobyl Exclusion Zone.

The assessment of the fluctuating asymmetry based on measurement of the parameters of left and right parts of silver birch (Betula pendula (L.) Roth.) leaves and relative sizes of pairs of Scots pine (Pinus sylvestris L.) needles from the Chernobyl Exclusion Zone (ChEZ) was carried out. Twelve samples of both birch leaves and pairs of needles were collected from 10 trees at 5 sites in the Chernobyl Exclusion Zone and also at one control site located outside the ChEZ. Values of gamma dose rate in the air varied between the sites from 0.1 to 40 µGy h-1. Activity concentrations of 90Sr and 137Cs in the birch leaves varied over the range of 0.9÷2460 kBq kg-1 and 0.1÷339 kBq·kg-1 (DW), respectively. In addition to the above, in the Scots pine needles, these ranges were 0.7 ÷1970 kBq kg-1f for 90Sr and 0.1÷78 kBq kg-1 (DW) for 137Cs. From the values of the radionuclides activity concentrations in the plants, the internal dose rate is estimated to be in the range of 0.1 ÷ 274 µGy h-1. The main sources of the internal dose rate were radiation of 90Sr and 90Y. Indices of fluctuating asymmetry of silver birch leaves and Scots pine needles varied over the range of 0.048 ±â€¯0.007 ÷ 0.060 ±â€¯0.009 and 0.014 ±â€¯0.002 ÷ 0.018 ±â€¯0.002, respectively, and did not statistically differ for all experimental sites. The indices also did not depend on the external or internal dose rate of ionizing radiation for plants. The above findings seem to be consistent with other research effort in terms of understanding the response of organisms to chronic pollutant exposure and the long-term effects of large scale nuclear accidents.

The progeny of Chernobyl Arabidopsis thaliana plants does not exhibit changes in morphometric parameters and cellular antioxidant defence system of shoots.

Morphometric parameters and functional state of the cellular antioxidant defence system of shoots were studied in the progeny of Arabidopsis thaliana (L.) Heynh. (A. thaliana) plants, previously and chronically exposed in the Chernobyl Exclusion Zone (ChEZ). Changes in cellular antioxidant enzyme activities in the progeny of exposed plants were assumed because antioxidant status of cell may be altered by inherited epigenetic changes, resulting in changes in antioxidant-response genes expression. These changes can be inferred as induced expression of CAT and SOD genes was found previously for A. thaliana plants by another group of scientists. It is well-known that ionizing radiation may induce changes in hormonal-signalling net-work, shifting balance in growth factors that may cause changes in morphometric parameters of plants. Seeds from A. thaliana plants were collected in the ChEZ at different levels of the external dose rate from 0.28 ±â€¯0.01 to 12.93 ±â€¯0.08 µGy/h. Internal dose rate for parent plants was calculated on the basis of the activity concentration of 90Sr and 137Cs in the plants, using dose conversion coefficients for wild grass. Total dose rate, absorbed by parent plants, was calculated as the sum of the external and internal dose rate and was in a range between 2.8 ±â€¯0.2 and 99 ±â€¯8 µGy/h. Seeds were then grown in the standard laboratory conditions (nutrient-agar, light-dark cycle and appropriate temperature) to analyse morphometric parameters of seedlings and final germination percentage. No significant changes in the morphometric parameters (root length and rosette diameter of shoots) of the seedlings were observed. Changes in the final germination percentage of the studied seeds were found, but low correlation was observed between found changes and the dose rate, absorbed by parent plants. In contrast to the results obtained in A. thaliana plants directly sampled in the field, no effect on the functional state of the cellular antioxidant defence system of shoots in the progeny of Chernobyl A. thaliana plants was observed.