| Mushroom fruiting bodies delicate texture, nutrient-rich, many of which also has a variety of health care, and play an important role in the transformation of waste materials of agriculture and forestry crops. In recent years, it was showed that a part of the edible mushrooms has a certain effect on heavy metal accumulation. Heavy metal pollution problems caused by the quality and safety of edible mushrooms were widespread concerned.In this study, the most widely cultivated mushroom, A. bisporus was used as expermental material. Lead and cadmium pollution condition and their sources were analyzed in A.bisporus. And then effects of Cd, Pb stress on mycelia and related enzymes of mycelia were studied. Lead and cadmium adsorption characteristics of mycelia in A.bisporus were discussed, and harmful heavy metals lead, cadmium accumulation distribution rules in fruiting bodies of A.bisporus was studied, including lead and cadmium speciation analysis, to reveal the mechanism of Heavy metals adsorption in A.bisporusAnalysis of heavy metals lead and cadmium contents of 51 samples in A. bisporus fruiting body showed the background values of lead and cadmium were 0.636 mg/kg and 0.127 mg/kg. lead contents of the samples is in the range 0.087 mg/kg～2.40 mg/kg, and cadmium contents in the range 0.038 mg/kg-0.301 mg/kg. Correlation analysis of lead and cadmium contents of 29 series samples (including fruiting body, compost and covering soil) between two cultivation modes showed that lead of fruiting body was mainly from the covering soil and has not relation with the compost. However, Cadmium content in fruiting body was influenced by both compost and covering soil.The results showed that with the lead and cadmium concentration increased, Distinct inhibiting effect was observed on mycelial growth rate and yield. Under stress of lead, cadmium, SOD, POD and CAT activity of three protective enzymes in mycelia showed a "low to promote and high-suppression" trend, and significant positive correlation and synergistic effect were detected between any two of them.With the increase of initial Pb(Ⅱ) and Cd(Ⅱ) concentration, The mycelial adsorption of A. bisporus presented "S" shaped curve, and The maximum adsorption amount of Pb(Ⅱ) and Cd(Ⅱ) are 45.19 mg/g and 46.49 mg/g, respectively.the optimal pH of Pb (Ⅱ) and Cd (Ⅱ) were 4.0 and 6.0, respectively, and the optimal shaking speed were 100 r/min and 50 r/min.The optimum temperature were 30℃～35℃and 25℃. mycelial adsorption of Pb(Ⅱ) and Cd(Ⅱ) can be divided into two stages:the first Pb (Ⅱ) and Cd (Ⅱ) in the rapid integration of mycelial surface The first phase of Pb(Ⅱ)and Cd(Ⅱ) was rapid integration on the surface of mycelia, the second phase of Pb(Ⅱ)and Cd(Ⅱ) adsorption slowly being transferred to the internal mycelial.The enrichment ability of plants in heavy metals is in the order:Cd> Pb. Reference to China's agricultural industry standards NY5095-2006 national limit standard (Pb≤2.0 mg/kg, Cd≤0.2 mg/kg), it was determined that the critical values of lead and cadmium in compound were 56.8 mg/kg and 1.41 mg/kg.Under Pollution-free conditions, The lead and cadmium contents of stipe were significantly lower than those of cap and gill. Under Polluted conditions, the lead content of stipe was significantly higher than gill and cap, but the distribution of Cd is still the same with Pollution-free. The absorption Pb and Mn was significantly correlated (P< 0.01), and Cd and Cu was significantly positively correlated (P< 0.01) in fruiting body.Pb was mainly in the acetic acid extractable form (FHAc) in A. bisporus, followed by hydrochloric acid extractable form (FHC1) and sodium chloride extractable form(FNaCl), and the other forms were low. Cd was mainly in sodium chloride extractable form(FNaCl), followed by acetic acid extractable form (FHAc), and the other forms were low. |
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