Effect of Ni and As on radish tuber cultivated on artificially polluted soils

A pot experiment with step contamination of soil by Ni and As was performed over a 2-year period with radish. Two soils were used (heavy soil – clay-loam – and light soil – sand-loam) and four levels of contamination were selected, based on the natural abundance of the elements in these soils. Addition of Ni or As had a different inhibiting effect due to the soil quality. With Ni, the biomass production was lower in light soil, whereas with As, this reduction of plant growth was stronger in heavy soil. The ultrastructure of Ni and As contaminated tubers was investigated both in the cortical and vascular bundle cells. The cytological study demonstrated that the two pollutants induced ultrastructural changes in mitochondria. They were more obvious in the vascular tissue than in the cortex and were correlated with the growth inhibition observed in both soils. Plant tolerance to Ni and As was coherent with the content of the mobile fractions of the two elements in soil.