ANTIOXIDATIVE ACTIVITY AND DIFFERENTIAL RESPONSE OF FUNGUS (Agaricus bisporus) TO HEAVY METALS

Plants possess cellular mechanisms to detoxify heavy metals and confer plants for better tolerance against them. It has been indicated that on metal-contaminated soils, ectomycorrhizal (ECM) fungi may improve plant growth through an enhanced nutrition or by alleviation toxicity of the metals. Agaricus bisporus (J. Lange), an edible mushroom has been observed to grow under pistachio trees (Pistacia vera L.) plantations in orchards of Kerman, Iran and it may forms ectomycorrhiza with the tree.

In this research the effect of different concentrations (0, 15, 30, 45, 60 mg/L) of various heavy metals Zinc (Zn), Nickel (Ni) and Mangenese (Mn) on fungal colony diameters and mycelial dry weights, heavy metals accumulation and antioxidative enzymes was studied in A. bisporus. The result showed there was a strong variation in metal tolerance, so that A. bisporus was more tolerant to Mn than other metals, so that the fungus had an increased growth in the presence of low concentrations of Mn and Zn but Ni greatly inhibited increase in biomass and colony diameter even at concentrations as low as 15 mg/L. Heavy metals caused an induction in Superoxide dismutases (SOD), catalase (CAT) activity up to 45 mg/L, but increase metal concentration above 45 mg/L resulted in significant decrease enzyme activities to control. With increase in the concentrations these heavy metals, the amount of metals in mycelium were increased too.