Interactions between selenium and iodine uptake by spinach (Spinacia oleracea L.) in solution culture

Interactions between Se (as selenate) and I (as iodate) uptake by spinach plants (Spinacia oleracea L.) were studied under controlled conditions using solution culture. Spinach readily accumulated both Se and I in the edible parts, the leaves, with solution-to-leaf transfer factors ranging from 3.5 to 13.4. The distribution coefficients between leaves and roots ranged from 4.07 to 5.66 for I and 4.51 to 8.59 for Se. Selenium concentrations in plant tissues were unaffected by addition of I to the nutrient solution. Similarly, plant I concentrations were unaffected by addition of Se to the nutrient solution, except in nutrient solution with I at a concentration of 50 muM, in which addition of Se lowered shoot I concentrations significantly, but the effect was of low magnitude. These results indicate the possible feasibility of dual supplementation of plant growth substrates with Se and I to improve human nutrition where these two elements are deficient in the diet. The data also indicate the involvement of a positive feedback mechanism in the uptake of Se by spinach plants, since Se concentrations in leaves increased disproportionately with increasing Se concentration in the nutrient solution.