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EFFECT OF RADIOACTIVE METAL IONS ON WHEAT: IN SEARCH FOR A BIOCHEMICAL MARKER

Manuela Murariu, Karin Popa

Abstract

Heavy and radioactive metal poisoning has become a problem of current interest as a result of environmental pollution on a global scale. Studies to test the noxious effect of radioactive metal ions on wheat germination and seedling growth showed that germination rate, shoot length, and fresh weights varied as a function of their concentration in the treatment solutions. We report here the effect of some radioactive and non-radioactive (stable) elements on the wheat seeds and seedlings (Triticum aestivum L.) in the seven day germination experiments, in which the shoots and roots are cut from the seeds, and their height, weight, and the residual radioactivity in each part measured. Thus, at the same concentration, the radioactive mercury proved to be more harmful to the living seeds and seedlings that the nonradioactive one. The protective action of glutathione against both radioactive and non-radioactive mercury was noticed. Thus, the mean shoot length decreased from 8.1 (control) to 4.6 cm (non-radioactive mercury) or even to 2.5 cm (203Hg), while glutathione had both an anti-toxic and an anti-radiotoxic effect (6.4 and 6.0 cm, respectively). The mean root weight of the lots decreased from 1.7 g (control) to 0.7 g and 0.4 g, respectively, while glutathione proved its recovering action (1.5 and 1.7 g). In another test, the radioactive mercury accumulated especially in roots an less in shoots; sugar seems to be the most important in the 203Hg2+ accumulation. Glutathione diminished the radiotoxic effect of 203Hg2+ as shown by the shoot weight and length of the lots (1.79 g and 310.2 cm in the case of glutathione and 203Hg2+ versus 1.56 g and 249.0 cm for the 203Hg2+ treatment). Not only cysteine but also cystine, which contains a пїЅS-S- bond in its molecule had also a significant protective effect, whereas some synthetic peptides used in our experiments proved to be harmful on seeds. Besides, 137Cs+ and 60Co2+ showed an inhibitory effect on the wheat germination as compared with the corresponding stable ions. The mechanism of radioprotection by these compounds is also discussed. Uranium proved to be none (radio)toxic to wheat as compared with other natural and anthropogenic radio cations, probably because its uptake by spring wheat during the germination is low. Indeed, only a small fraction of uranium administered was located within the roots, whereas the uranium content of the stems was negligible. Taken together, our results demonstrate that wheat seeds could be a marker for the effect of both radioactive and nonradioactive metals and that some SH-group containing natural compounds might have a protective role against such elements found in increasingly higher amounts in the environment.

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DOI resolver: doi.org/10.5593/sgem2017/51/s20.045

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