Tolerance And Accumulation Characteristics Of Cadmium In Amaranthus Hybridus L.

In order to investigate Cd tolerance, uptake and accumulation by Amaranthus hybridus L., the soil culture, hydroponics experiment, fertilizer test and plot experiment were taken following a field survey. The main results showed as follows:(1) The A. hybridus L. showed great tolerance and accumulation characteristics of cadmium in the soil culture and hydroponics experiment. A. hybridus grew normally at added Cd concentrations≤90 mg kg-1 and≤10 mg L-1 in the soil culture and in the hydroponics solutions, respectively. In the high Cd treatment, such as 180 mg kg-1 and 40 mg L-1, the plant can also exist.At Cd levels≤30 mg kg-1 in the soil culture, the plant height and the root length were larger than the control (0). And at Cd levels≤10 mg L-1 the root length and the pant height had no significant difference with the control (P> 0.05). At Cd levels≤90 mg kg-1, the shoot biomass and root biomass were larger than the control. But at Cd levels≤10 mg L-1, the shoot biomass and root biomass had no significant difference with the control (P> 0.05). In the hydroponics solutions, peroxidase activity showed a quadratic relationship and catalase activity changed irregularly with increasing Cd concentrations.At Cd concentrations up to 120 mg kg-1 in the soil culture and 20 mg L-1 in the hydroponics experiment, Cd concentrations in shoots were 128.39 mg kg-1 and 173.10 mg kg-1, both of them became more than 100 mg kg-1, which is regarded as the threshold value of Cd-hyperaccumulators. The highest Cd concentrations in shoots in the soil culture and hydroponics experiment were 241.56 and 354.56 mg kg-1, respectively, when the Cd concentrations up to 180 mg kg-1 in the soil culture and 40 mg L-1 in the hydroponics experiment. The highest shoot accumulations of Cd in the soil culture and hydroponics experiments were 1006.95 and 668.42μg pot-1, respectively. Shoots accumulated more Cd than roots accounting for 80.5-94.8% in soil culture and 24.4-62.6% for the hydroponics experiment of the total plant accumulation. Bioconcentration factors in soil culture and hydroponics solutions were 0.58-1.22 and 5.18-17.55, and translocation factors were 0.64-1.50 and 0.33-0.92, respectively.(2) In the fertilizer test of N, P, K, the certain concentration of N and K can promote the uptake of Cd in A. hybridus. At the N concentration of 100-300 mg kg-1, the plant biomass and Cd accumulation were increasing significantly (P<0.05). The Cd concentration and accumulation reached to the maximum at the N concentration of 150 mg kg-1. POD and CAT activities increased with increasing N concentration. There were no significant difference for Cd concentration and shoot biomass(P> 0.05), when the P was added in the soil. At the K level of 100 mg kg-1, the highest Cd concentration and accumulation were 27.96 mg kg-1 and 644.63μg pot-1, respectively.(3) The A. hybridus had great potential phytoremediation capability in Cd polluted soils. In the plot experiment, the largest shoot biomass was up to 125.50 g. The Cd concentrations were 17.26 to 52.22 mg kg-1. The shoot accumulations accounts for 79.40%-98.64% of the total plant accumulation. The BCFs were 31.35-607.76 and the TFs were 0.49-3.49.