Selenium uptake and its antioxidant role in ryegrass cultivars as affected by selenite seed pelletization

A greenhouse study was carried out to evaluate the effect of seed pelletization with increasing selenite doses (from 0 to 60 g Se ha ^-1) on the yield, Se uptake and the antioxidant responses of three ryegrass cultivars (Aries, Nui and Quartet) cultivated on an Andisol during two consecutive growth periods. In addition, a second assay was conducted to determine the residual effect of Se in the shoots during four consecutive plant cuts. Results showed that selenite-pelleted seeds at rates up to 60 g Se ha ^-1 did not influence the yield of shoots and roots of the three ryegrass cultivars. Selenium concentration in shoots and roots steadily increased as a consequence of increased Se supply, and it was accumulated mainly in the roots. Plants of the different cultivars accumulated similar amounts of Se in their shoots, but Quartet roots built up greater Se concentration than those of Aries or Nui at rates of application above 35 g Se ha ^-1. Whereas Se doses above 10 g ha ^-1 increased the shoot Se concentration in the two yields of the three ryegrass cultivars to suitable levels according to the minimum dietary requirement of beef and dairy cattle, the residual effect of Se was maintained through four cuts at Se supply of 30 and 60 g ha ^-1. Likewise, the different cultivars displayed differential patterns of lipid peroxidation in response to the added Se. During the growth period, reductions of the oxidative damage of membranes were accompanied by inhibition of SOD in Aries and Nui and by the activation of GSH-Px antioxidant enzymes in the three ryegrass cultivars. Thus, in our study the benefits of Se on the plant health were closely related to an enhancement of the antioxidant system in the ryegrass cultivars. In summary, our results indicate that selenite-pelleted ryegrass seeds seem to be a promissory tool to increase both the Se content and the antioxidant ability of pastures. Its potential use requires, however, to be evaluated under field conditions in Se deficient soils.