Remediating soil contaminated with heavy metals using macrofungi is a novel approach in studying environmental remediation. The key issue in bring this approach into large-scale practical application lies in the success of screening out a series of ideal hyperaccumulators of heavy metals. Plate cultivation was adopted to evaluate the mycelial growth tolerance and the accumulation characteristics to heavy metals Cr, Pb and Mn respectively in two species of macrofungi, Pleurotus pulmonarius and Panus giganteus, in terms of colony diameter, mycelial dry weight and heavy metal content in mycelia. The results showed that the Cr tolerance in the two species were similar. The diameter of the colonies and the dry weight of the mycelia in the two species showed an initial increase with the increase in Cr concentration in the substrate in a small range of low Cr concentrations, but followed by a steady decrease when the Cr concentration was progressively increased. The threshold Cr concentration for 50% growth inhibition was 200 mg/L for both species. The maximal tolerant concentrations (MTC) of Cr for them were all 500 mg/L. P. pulmonarius was very sensitive to Pb and the mycelial growth could be significantly inhibited, with the 50% growth inhibition appearing at a Pb concentration of 100 mg/L (P＜0.01). In contrast, P. giganteus showed a very high tolerance toPb, being able to grow normally in substrate containing Pb of up to 500 mg/L in concentration. In terms of colony diameter and mycelial dry weight, no significant difference (P＞0.05) was seen between the group treated with 500 mg/L Pb and the control group, with the 50% growth inhibition occurring at a Pb concentration of 700 mg/L. The Pb MTCs were 1000 mg/L and 2000 mg/L for P. pulmonarius and P. giganteus, respectively. It is therefore concluded that P. giganteus has a higher tolerance to Pb than P. pulmonarius. Mn showed increasing inhibition effects on the growth of P. giganteus with increasing Mn concentrations, and the 50% growth reduction was observed at a Mn concentration of 1000 mg/L in the growth substrate. The MTC of P. giganteus forMn was 6000 mg/L. P. pulmonarius exhibited a lower tolerance to Mn. Cr and Pb were not able to be hyperaccumulated by P. pulmonarius, while Cr and Mn were not able to be hyperaccumulated by P. giganteus. On the other hand, P. giganteus could hyperaccumulate Pb up to 1125.56 mg/kg (dry weight) in its mycelia, having approached the level of hyperaccumulation.
Some wild macrofungi bioaccumulating heavy metals effectively could not be artificially cultivated, which limited their application in environmental remediation. So the potential application of artificial or semi-artificial cultivating macrofungi for environmental remediation was suggested. If large-scale screening of macofungi for heavy metal hyperaccumulator through normal cultivation is conducted for that application, the workload will be too heavy, time consuming and low yielding. On the contrary, plate cultivation can reduce most of the workload, for the method is simple and rapid in detecting the mycelial growth tolerance and accumulation characteristics to heavy metals, making the screening of macrofungi with hyperaccumulation ability to heavy metals more effective, thus paved the way for potential large-scale application. Our results that P. giganteus selected viaplate cultivation could survive Pb concentrations up to 500 mg/L and could hyperaccumulate Pb up to 1125.56 mg/kg in its mycelia have verified this point.