Effects of Nano-maghemite on Trace Element Accumulation and Drought Response of Helianthus annuus L. in a Contaminated Mine Soil

Although recent studies show that the iron oxides do not enter or accumulate in plants, they may preclude the transport of water and nutrients in the plants through/as a consequence of their aggregation on the surface of the roots. The feasibility of using iron oxide nanoparticles to modify the availability of trace elements (TEs) to Helianthus annuus in the soil as well as their interference with the plant response during an imposed water deficiency stress were studied in a pot experiment. Plants were grown in a compost preamended contaminated soil with and without nanomaghemite (NM) and later exposed to drought. The nano-amendment promoted the growth of H. annuus (higher (25 %) dry weight than in the same soil without NM), mainly due to the in solubilisation of pore water Zn in the soil and the consequent reduction of its availability to the plants. During the water stress, NM did not cause an increase in the accumulation of proline or total amino acids in the plants, which are normally used as drought stress indicators, compared to the control plants without NM. In conclusion, NM could be useful soil amendments during phytoremediation procedures, since it can immobilise TEs in the soil without disrupting the plant water balance.