SALINITY AND BORON TOLERANCES OF CANDIDATE PLANTS FOR THE REMOVAL OF SELENIUM FROM SOILS

Agricultural drainage water from the west side of the San Joaquin Valley, CA is highly salinized, and is often contaminated with an assortment of metals and metalloids, including Se. Among proposed disposal options, vegetation management may be a critical component of remediation strategies designed to reduce soil or sediment concentrations of Se to safe levels. Soil salinity (mostly sodium sulfate) and B pose serious limitations to the use of many plant species. We screened a number of cultivars or lines of species from the genera Astragalus, Leucaena, Medicago, Trifolium, Elymus, Elytrigia, Festuca, Leymus, Oryzopsis, Psathyrostachys, Puccinellia, and Sporobolus for tolerance to salinity and B using solution culture methods. Considerable variation in tolerance to salinity, both within and across species, was observed during seed germination. Electrical conductivities required to produce a 50% reduction in germination (EC50) ranged from 5 to 30 dS m-1. Boron levels up to 4.0 mM had only minimal effects on germination. The most promising genotypes, representing some 15 species, were then tested for salinity and B tolerance during the seedling growth stage. Lines of five species (Astragalus bisulcatus, A. racemosus, Elytrigia pontica, Puccinellia distans, and Sporobolus airoides) appeared most promising; all exhibited EC50 values > 20 dS m-1 and were unaffected by B concentrations up to 4.0 mM during seedling growth. Astragalus bisulcatus and A. racemosus are considered primary accumulators of Se; their tolerance of high salinity and B during seedling growth make them particularly good candidates for remediation of Se-enriched soils and sediments.