Effect of antimony in soils of an Sb mine on the photosynthetic pigments and antioxidant system of Dittrichia viscosa leaves

Antimony is a toxic element whose concentration in soil and water has been rising due to anthropogenic activities. This study focuses on its accumulation in leaves of Dittrichia viscosa growing in soils of an abandoned Sb mine, and the effect on oxidant/antioxidant systems and photosynthetic efficiency. The results showed leaves to have a high Sb accumulation capacity. The amount of total chlorophyll decreased depending on Sb concentration and of carotenoids increased slightly, with a consequent increase in carotenoid/chlorophyll ratio. Photosynthetic efficiency was unaffected. The amount of O₂^.- rose, although there was no increase in cell membrane damage, with lipid peroxidation levels being similar to normal. This response may be due to considerable increases that were observed in total phenolics, PPO activity, and enzymatic antioxidant system. SOD, POX, and DHAR activities increased in response to increased Sb amounts in leaves. The ascorbate/glutathione cycle was also affected, with strong increases observed in all of its components, and consequent increases in total contents of the ascorbate and glutathione pools. However, the ratio between reduced and oxidized forms declined, reflecting an imbalance between the two, especially that between GSH and GSSG. Efficient detoxification of Sb may take place either through increases in phenolics, carotenoids, and components of the glutathione-ascorbate cycle or through the enzymatic antioxidant system. Since Dittrichia viscosa accumulates large amounts of Sb without suffering oxidative damage, it could be used for phytoremediation.

Keywords: Antimony; Antioxidant system; Ascorbate; Dittrichia viscosa; Glutathione; Phenols; Photosynthetic pigments.