ACCUMULATION OF SELENIUM BY DIFFERENT PLANT-SPECIES GROWN UNDER INCREASING SODIUM AND CALCIUM-CHLORIDE SALINITY

High levels of naturally occurring selenium (Se) are often found in co njunction with different forms of salinity in central California. Plan ts considered for use in phytoremediation of high Se levels must there fore be salt tolerant. Selenium accumulation was evaluated for the fol lowing species under increasing salt (NaCl and CaCl) conditions: Brass ica napus L. (canola), Hibiscus cannibinus L. (kenaf), Festuca arundin acea L. (tall fescue), and Lotus tenuis L. (birdsfoot trefoil). The ex perimental design was a complete randomized block with four salt treat ments of < 1, 5, 10, and 20 dS m(-1), four plant species, three blocks , and six replicates per treatment. Ninety days after growing in the r espective salt treated soil with a Se concentration of 2 mg Se kg(-1) soil, added as Na2SeO4, all plant species were completely harvested. A mong the species tested, shoot and root dry matter yield of kenaf was most significantly (p < 0.001) affected by the highest salt treatment and tall fescue and canola were the least affected species. Generally there was a decrease in tissue accumulation of Se with increasing salt levels, except that low levels of salinity stimulated Se accumulation in canola. Canola leaf and root tissue accumulated the highest concen trations of Se (315 and 80 mg Se kg(-1) DM) and tall fescue the least (35 and 7 mg Se kg(-1) DM). Total soil Se concentrations at harvest we re significantly (p < 0.05) lower for all species at all salt treatmen ts. Removal of Se from soil was greatest by canola followed by birdsfo ot trefoil, kenaf and tall fescue. Among the four species, canola was the best candidate for removing Se under the tested salinity condition s. Kenaf may be effective because of its large biomass production, whi le tall fescue and birdsfoot trefoil may be effective because they can be repeatedly clipped as perennial crops.