Salinity-heavy metal interactions in four salt-tolerant plant species

The concurrent effect of NaCl salinity and heavy metals [cadmium (Cd), chro mium (Cr) and nickel (Ni)] on growth, sodium (Na), and heavy metal accumula tion was assessed in four salt tolerant plant species. These were: barley ( Hordeum vulgare L.), purslane (Portulaca oleracea L.), Inula crithmoides L. , and Plantago coronopus L., all of which have documented potential for use in saline agriculture. Plants were grown in perlite and irrigated with sal inized and non-salinized nutrient solutions (9 dS m(-1) and 18 dS m(-1)) co ntaining 2 ppm Cd, 4 ppm Cr, 10 ppm Ni, and a non-metal control. Salinity, Cd, and Ni caused a significant decrease in the dry biomass accumulation of P oleracea, but had no effects on other plant species. Sodium accumulation was highest in P coronopus and I. crithmoides, indicating pronounced halop hytic properties. The presence of heavy metals reduced Na accumulation in H . vulgare and P oleracea, but had no effect on P coronopus and I. crithmoid es, indicating that the Na-heavy metal interaction is plant-specific . Meta l accumulation in the four plant species was generally enhanced by the 9 dS m(-1) treatment, but not by the 18 dS m(-1) treatment. This could indicate the presence of an ionic exclusion mechanism operating at high salinity le vels that would operate indiscriminately on Na as well as on Cd, Cr, and Ni .