Rates of Selenium Volatilization among Crop Species

Abstract

The rate of Se volatilization per plant was measured for 15 crop species grown hydroponically (for 18–48 d depending on the species) in growth chambers. Selenium was supplied as 20 micromolar sodium selenate in 0.25 strength Hoagland's solution. Selenium volatilization was determined by enclosing plants in a Plexiglas plant chamber and trapping the volatile Se emissions in alkaline peroxide traps. The results show that rice (Oryza sativa L.), broccoli (Brassica oleracea botrytis L.), and cabbage (Brassica oleracea capitata L.) volatilized Se at the fastest rates, i.e., 200 to 350 µg Se per m 2 leaf area per day (1500–2500 µg Se kg−1 plant dry wt. d−1). Carrot (Daucus carota L.), barley (Hordeum vulgare L.), alfalfa (Medicago sativa L.), tomato (Lycopersicon esculentum Mill.), cucumber (Cucumis sativus L.), cotton (Gossypium hirsutum L.), eggplant (Solanum melongena L.), and maize (Zea mays L.) had intermediate rates of 30 to 100 µg Se m−2 d−1 (300–750 µg Se kg−1 d−1). Sugarbeet (Beta vulgaris L.), bean (Phaseolus vulgaris spp.), lettuce (Lactuca sativa L.), and onion (Allium cepa L.) had the lowest rates, i.e., less than 15 µg Se m−2 d−1 (<250 µg Se kg−1 d−1). Comparing all plant species, Se volatilization rate was found to be highly correlated with Se concentration in plant tissues; we suggest that the ability of plants to absorb Se may be an important factor contributing to high rates of Se volatilization.