Abstract

Selenium (Se) is regarded as an antioxidant in animal and human nutrition, but its biological role in plants needs to be clarified. Plants vary considerably in their ability to tolerate Se, and their biochemical response to Se may be affected by liming or P fertilization. Two greenhouse experiments were conducted with white clover (Trifolium repens L.) to evaluate Se accumulation, tolerance, and the antioxidant response at increasing selenite supply levels (from 0 to 60 g Se ha -1) and the effect of lime and P on both the Se uptake and the antioxidant activity of plants treated with 0, 20 and 40 g Se ha -1. Selenium concentration in plant tissues was increased by Se applications, and plant growth was reduced at Se supply levels above 20 g ha -1. At shoot concentration up to 200 μg kg -1 DW, Se promoted antioxidant ability by increasing the free radical scavenging activity and by inhibiting lipid peroxidation (TBARS), whereas above this level TBARS accumulation increased. Significant changes in the activities of peroxidase (POD) and ascorbate peroxidase (APX) enzymes were also observed as a consequence of the increase in shoot Se concentration. The application of lime and P improved the plant nutrition, which increased the dry matter yield and enhanced the plant's antioxidative system. Under different combinations of soil acidity and P fertilization a differential uptake of Se by the plant occurred. These factors appear to be responsible for beneficial or detrimental effects of Se in terms of lipid peroxidation of biological membranes and the activation of POD and APX in white clover. © 2007 Springer Science+Business Media B.V.