Selenium Toxicity in Perennial Ryegrass and White Clover

Abstract

Summary Shoot concentrations of Se associated with a 10% reduction in dry matter yield were established for perennial ryegrass (Loliumperenne L.) and white clover (Trifolium repens L.) grown in sand culture. Selenite– treated plants had lower shoot concentrations of Se than those treated with selenate; the critical toxic values associated with a 10% reduction in growth were 48 and 320μg Se g− 1 dry matter shoots for ryegrass plants, and 160 and 330μeg1 dry matter shoots for white clover plants, respectively. Differences in the mode of absorption of selenite and selenate, and in the distribution and chemical form of Se found in the plant after absorption, probably account for this disparity in toxicity. While both selenate and selenite increased the Se concentration in the tissues of the plants to high levels, a greater proportion of the absorbed Se was transported to the shoots of the selenate‐treated plants than of those treated with selenite. Increasing supplies of selenate were associated with a reduction in chlorophyll content. Contrary to the concept of a common uptake mechanism in the roots for selenate and sulphate, increasing supplies of selenate had a synergistic effect on S concentrations in the shoots rather than the expected antagonistic effect.

Selenato e selenito na produção, nutrição mineral e biofortificação com selênio em cultivares de alface¹

“…Assim, alterações na absorção e no teor de S promovidas pelo Se são esperadas, tal como observado por Smith & Watkinson (1984), Banuelos et al (1990), Mikkelsen & Wan (1990) e Barack & Goldman (1997). No presente estudo, o aumento nas concentrações de selenato aumentou o teor de S em todas as cultivares de alface, tendo a maior concentração proporcionado os maiores teores de S (Figura 2a).…”

Variation in [75Se]selenate uptake and partitioning among tomato cultivars and wild species

“…It appears, however, that the interaction between sulphate and selenate is more complex than can be explained simply by competitive inhibition for uptake. Smith & Watkinson (1984) and Mikkelsen et al (1988) both observed synergistic effects of selenate on sulphate accumulation, as measured by shoot S content, in monocot and dicot species grown at low sulphate concentrations. The basis of this synergism is not understood.…”

Effects of selenium as a beneficial element on growth and photosynthetic attributes of greenhouse cucumber

“…In tomato leaves, the interaction of Se in 0, 0.5, 1, and 2 ppm levels with MO on photosynthetic pigments indicated no significant effect on shoot dry weight and total plant dry weight, however root dry weight significantly reduced (Khavarinejad et al, 2010 Lefsrud et al, 2006;Padmaja et al, 1990;Valkama et al, 2003;Xue et al, 2001). In ryegrass and white clover, by increasing Se concentration chlorophyll content decreased (Smith and Watkinson, 1984). In coffee and corn, different levels of Se in a form of selenite decreased photosynthetic pigments, including chlorophyll, carotenoids and xanthophylls in coffee and chlorophyll formation rate in corn (Jain and Gadre, 1998;Mazzafer, 1998).…”

“…The relationship between soil pH and the amount of absorbed Se by plants showed increased soil pH increased Se absorption (Malakooti and Tehrani, 2005). Plants show different physiological reactions to Se levels, some species accumulate it, but some others are sensitive to it and Se is a toxic element to them (Smith and Watkinson, 1984 with Se addition to soils (Hanson et al, 2004;Lyons et al, 2008). Using Se fertilizer under oxidative stress on broccoli reduced (deoxyribonucleic acid) DNA rupturing and breaking (Arvy et al, 1995).…”