Evaluation of Flax Plant as a Cadmium Phytoremediator for Polluted Soils under Different Chemical and Biological Treatments

A pot experiments was carried out in the greenhouse of Faculty of Agriculture Cairo University during the two successive winter seasons (2015-2016 and 2016-2017) to evaluate the potential of  flax plants (Linum usitatissimum L.) as a Cd tolerant and accumulator for polluted soils. The experiment was laid out in a split-plot design with a randomized-complete design in three replicates. Surface sandy loam soil samples (0-20 cm) were collected from Abou-Rawash area, which received sewage sludge and sewage effluent for long time ( about 20 years).Three levels of soil Cd (initial 3.13), and two artificial ones 50 and 75mg kg^-1 soil, were prepared using CdCl₂ solution by wet and dry process for three months. The chemical (EDTA) and biological (AMF and Thiobacillus) treatments were allocated to sub plots. Each sub plot consisted of pots each containing 10kg soil and 100 flax plants. The results showed that by increasing soil cadmium levels, the flax plant dry weight (roots, stem and leaves) significantly decreased. Under different levels of soil Cd, the chemical and biological treatments recorded variable changes in flax plant dry weight. The highest increases in dry weight was recorded with AMF treatment (5.63 and 8.50% in 1^st and 2^nd seasons, respectively, with an average of 7.06%) compared with the control (initial).However, cadmium contents in the different parts of flax plant increased with increasing soil cadmium levels. The highest Cd concentration in flax roots, stem and leaves recorded in EDTA treatment which lead to increases of 1.73, 2.11 and 1.88 folds in roots, stem and leaves, respectively, compared with untreated soil at 75 µg Cd g^-1  soil. The uptake of Cd by flax substantially affected by both levels of Cd in soil and different soil treatments. The highest Cd uptake was found in 75 µg g^-1 soil level followed by 50µg g^-1 and the lowest in 3.13 µg g-¹ soil. Flax was uptake and accumulate cadmium from the soil with distributing evenly throughout plants (roots < stem < leaves). Both EDTA and AMF treatments recorded the highest phytoextraction of Cd from contaminated soil. Finally, the obtained results suggest that, flax plant can be considered as a Cd tolerant which can accumulate Cd, especially, with mycorrhiza fungi and EDTA treatments but could not be considered a hyperaccumulator of Cd from polluted soils.