Effect of selenium on growth and antioxidant capacity of Triticum aestivum L. during development of lead-induced oxidative stress

Effects of two selenium concentrations—0.4 and 0.8 mg Se 6+ per kilogram of soil (treatments Se0.4 and Se0.8)—on seedling growth, chlorophyll content (Chl ( a + b )), the content of thiobarbituric acidreactive substances (TBARs) indicative of peroxidation rates, and the activities of antioxidant enzymes (ascorbate peroxidase, AsP; glutathione reductase, GR; and guaiacol peroxidase, GPX) were studied in roots and leaves of wheat ( Triticum aestivum L., cv. Triso) plants that were exposed for 14 days to oxidative stress induced by 50 and 100 mg Pb 2+ per kilogram of soil (treatments Pb50 and Pb100, respectively). The pollution of soil with Pb 2+ inhibited growth, lowered Chl ( a + b ) content, and intensified peroxidation. The content of TBARs increased by 44 and 72% in leaves and by 25 and 45% in roots for treatments Pb50 and Pb100, respectively. Activities of the antioxidant enzymes GR and GPX were higher in Pb 2+ -treated than in untreated (control) plants. The introduction of Se 6+ into Pb 2+ -free soil (treatment Se0.4) was found to promote growth, stimulate AsP activity by 40% in leaves, and enhance AsP, GR, and GPX activities in roots by 38, 33, and 74%, respectively. The content of TBARs was reduced in Se 6+ -treated plants. By contrast, the treatment Se0.8 suppressed growth, elevated TBARs content, and stimulated activities of antioxidant enzymes in roots and leaves. The addition of 0.4 mg Se 6+ /kg to Pb 2+ -contaminated soil alleviated the negative influence of lead on plant growth, whereas the addition of 0.8 mg Se 6+ /kg aggravated the effect of Pb 2+ contamination, especially in treatment (Pb100+Se0.8). Thus, the effectiveness of exogenous Se 6+ application on growth and adaptive potential of plants cultivated under optimal pollutant-free conditions and on soils contaminated with lead depended on the concentration of Se 6+ supplemented to soil and on the content of the stressor agent.