Growth and Physiology of Maize (Zea mays L.) in a Nickel-Contaminated Soil and Phytoremediation Efficiency Using EDTA

Nickel (Ni) element is strongly phytotoxic at high concentrations for several plants, but due to its dual behavior and complicated chemistry, it has received little attention in plant nutrition and relevant experimental data are limited. The current research was carried out to study the effect of Ni on maize (Zea mays L.) growth and phytoextraction potential with EDTA assistance, a process termed as chemical assisted phytoremediation. Treatments included two levels of EDTA (0 and 0.5 mM), two levels of Ni (0 and 40 µM) and their combination (EDTA+Ni) that were applied to maize plants grown in a pot experiment. Application of Ni alone or in combination with EDTA reduced maize root and shoot length by 7.8% to 13.3% and by 15.6% to 21.1%, respectively, compared with control, as well as root and shoot dry weight by 42.0% to 60.0% and by 29.8% to 46.6%, respectively. A similar declining trend was observed also for the content of photosynthetic pigments (chl-a, chl-b, total chlorophyll, and carotenoids) as well as total proteins. However, proline, total soluble sugars, and free amino acids showed an increasing trend with application of Ni and EDTA alone or in combination. These treatments significantly decreased P and Na content in maize roots, stems, leaves, and grains, while increased K content compared with control. Application of EDTA with Ni was the most effective treatment to enhance Ni accumulation in maize (50.23 mg per plant) compared with Ni alone (40.62 mg per plant), EDTA alone (27.75 mg per plant), and control (15.51 mg per plant). Application of EDTA in combination with Ni enhanced Ni accumulation by 4.9 folds in maize shoots and by 2.6 folds in roots over control. In conclusion, application of EDTA in suitable concentrations may enhance Ni uptake by maize providing an effective and economic phytoremediation method of Ni-contaminated soils.