Interactive Effects of Ni, Cr, Co, Ca, and Mgin Seeds Germination Test: Implicationsfor Plant Growth in Ultramafic Soils

Weathering of peridotites and serpentinites leads to the formation of ultramafic soils characterized by several peculiar properties such as low Ca/Mg ratios and elevated concentrations of Ni, Cr, and Co. The aim of our study was to investigate the effects of Ca2+ and Mg2+ on seed germination in the environment that mimic ultramafic and non-ultramafic soils. We hypothesized that Ca and Mg alleviate toxicity of Ni, Cr, and Co in relation to seed germination and root length. Regardless of concentration, metal salts inhibited seed germination and root growth for almost all studied plant species compared to control. An increase in germination was observed in treatments containing high concentrations of Ni2+ and Co2+ with the addition of Ca2+ and Mg2+. Roots of plants had greater length in high Ni2+ and Co2+-treatments with Ca2+ and Mg2+ in relation to metal treatments without the addition of Ca2+ and Mg2+. In low-content metal treatments with Ca2+ and Mg2+, roots had similar or smaller lengths compared to metal treatments. Our results demonstrate that Ca2+ and Mg2+ alleviate toxicity of Ni2+ and Co2+ during seed germination and root growth under conditions simulating ultramafic soils. Therefore, in soils derived from ultramafic rocks enriched in Ca, an increase in germination and root growth is expected as opposed to soils occurring on Ca- poor ultramafic rocks. In non-ultramafic soils containing relatively low amounts of Ni, Cr, and Co, the roles of Ca and Mg are negligible.