Antioxidant Enzymes and Functional State of PS II in Plants Grown under Various Radium (²²⁶Ra) Concentrations

Abstract

This work is devoted to study the antioxidant enzymes and functional state of photosystem (PS) II under the different concentrations of the radium in barley (Hordeum vulgare L.) and clover (Trifolium pratense L.) plants. It was determined that CAT activity increased in barley grown in the soil contaminated with low radium concentrations (29.45 ± 3.00 and 124 ± 15.00 Bq kg⁻¹) as compared with control, but decreased dramatically upon the effect of high radium concentration (242.25 ± 28 Bq kg⁻¹). CAT activity was 0.078 mmol/g min in control plants, and 0.18, 0.23 and 0.03 mmol/g min in 29.45 ± 3.00, 124 ± 15.00, 242.25 ± 28.00 Bq kg⁻¹, respectively. It was observed that in clover seedlings as the radium activity increased, CAT activity also rised, but at high concentrations, as well as in barley, enzyme activity decreased. The APX activity in barley as compared to the control decreased as a result of radium effect. APX activity in clover increased in soil with higher radium concentrations. SOD activity in barley increased at high levels of radium concentration (i.e. 0.5 unit/mg in the control, 0.6, 2.7 and 3 units/mg in 29.45 ± 3.00, 124 ± 15.00 and 242.25 ± 28.00 Bq kg⁻¹, respectively). In clover, changes in PS II activity decreased significantly at high ²²⁶Ra concentrations.