Accumulation of cadmium by flax and linseed cultivars in field-simulated conditions: A potential for phytoremediation of Cd-contaminated soils

The possibility of use of two technological types of Linum usitatissimum L., namely flax (grown for fibre) and linseed (grown for seed), for phytoextraction of cadmium (Cd) from Cd-contaminated soil was studied. A four-year field-simulated experiment was carried out with 6 flax and 4 linseed cultivars in order to study organ accumulation of Cd by flax and linseed plants at artificial concentration range 10–1000 mg Cd kg−1 soil. The most Cd was accumulated by roots, followed by shoots, while reproductive parts (capsules and seeds) played comparably smaller role. The increasing soil Cd concentration resulted in increasing Cd accumulation by roots, while transport to above-ground plant parts was progresivelly inhibited. Even high soil Cd concentrations (1000 mg Cd kg−1 soil) had not dramatic negative effect on plant growth and development. Cultivar differences as well as the differences between both technological Linum types have been found in Cd accumulation (flax being better Cd accumulator than linseed). Nevertheless, the recorded variation between technological types and within cultivars is in multiples of Cd values (units of mg Cd kg−1 DW), not in orders of magnitude as needed for practical phytoextraction. A significant year-to-year effect on plant growth/development resulting in high variation in Cd accumulation was observed. Flax cv. Jitka exhibited good transport of Cd from roots to above-ground parts, while flax cv. Merkur showed high retention of Cd in roots. Further, the contrasting cultivars in total Cd accumulation (high accumulating flax cv. Jitka versus low accumulating linseed cv. Jupiter) were selected for future experiments. The uptake of Cd by flax/ linseed from ha per season was calculated and the strategy for flax/linseed growing on heavy metal polluted soils with subsequent utilization of heavy metal-contaminated biomass is discussed.

Research highlights
► The differences exist between Linum technological types in cadmium accumulation.
► Increased Cd soil content results in high retention of Cd in roots.
► The variation in root-to-shoot Cd transport was found in 10 flax/linseed varieties.
► Fibre flax cv. Jitka was determined as the best Cd-accumulator.
► Flax/linseed is proposed for heavy metal phytoextraction of medium-polluted soils.