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Abstract
Contamination of soils with heavy metals such as Fe, Zn, Mn and Cu can occur naturally or as a result of a wide range of human industrial and agricultural activities. The uptake of such nutrients by mycorrhizae presents an interesting problem in toxic metal environments. Although the increased absorption of Fe, Zn, Mn and Cu or other necessary nutrients into the host plant by mycorrhizae is beneficial in nutrient-deficient soils, this is the same mechanism that may become deleterious when the metal content of soil reaches or is near a toxic levels. The prospect of VAM fungi existing in heavy metal-contaminated soils has important implications for phytoremediation.
The present investigation was carried out to assess the influence of mycorrhiza on the phytoremediation and translocation of Fe, Zn, Cu and Mn within both legumes and grasses plants. and to evaluate the ability of mycorrhiza to modify the dissteribution of these elements on plant tissue.
A greenhouse pot experiment was conducted using a polluted sandy soil collected from El-Gable El-Asfar area. The soil was irrigated with waste water effluent of Cairo sewage and fertilized with sewage sludge for more than 80 years. Pinecum, sorghum and soybean were used as test plants grown in the soil with and without vesicular arbuscular mycorrhizal fungi (VAM). Two plant samples were taken out, after 45 and 80 days from sowing to determine growth parameters; represented as fresh and dry weights, as well as four heavy metals; including Fe, Zn, Cu and Mn removal capacity from the soil.
The obtained results could be summarized in the following points:
• Inoculation with vascular arbscular mycorrhizae increased both the fresh and the dry weights of legumes represented by soybean and grasses represented by pinecum and sorghum.
• VAM infection significantly increased shoot dry weights by 151, 89 and 9.3% after 45 days and 163.0, 102 and 24% after 80 days for pinecum, sorghum and soybean, respectively.
• Root/shoot percentages were significantly lower in the VAM infected plants compared to non-infected ones.
• Plants inoculated with mycorrhizal accumulated significantly more iron, zinc, manganese and copper than un-inoculated plants. This finding was recorded in both shoots and roots of the three tested plants regardless of plant age. However, the effect of VAM fungal inoculation on metal accumulation has been shown to vary among the three studied plant types.