Subcellular distribution and chemical forms of cadmium in Morus alba L.

Morus alba L. (mulberry) is a perennial woody tree and a species with great potential for Cd phyremediation owing to its large biomass and extensive root system. The mechanisms involved in Cd detoxification were investigated by analyzing the subcellular distribution and chemical forms of Cd in mulberry in the present study. These results indicated that 53.27-70.17% of Cd mulberry accumulated was stored in the root and only about 10% were in the leaves. Lots of the Cd was located in the cell wall of the mulberry root and in soluble fraction of the mulberry leaf. Moreover, in roots, the largest amount of Cd was in the form of undissolved Cd-phosphate. While in mulberry leaves and stems, most of the Cd was extracted by 2% Acetic acid and 0.6 M HCl, representing Cd-phosphate and Cd-oxalate. It could be concluded that the Cd combination with peptides and organo-ligands in vacuole of leaf or complexed with proteins or cellulose in the cell wall of root might be contributed to the tolerance of mulberry to Cd stress. The mulberry could be used to remediate the Cd polluted farmland soils.

The mobility of cadmium and lead in the soil-mulberry-silkworm system.

Evaluation of the transportation of heavy metals in food chain has received a great deal of attention. In this study, the mobility of cadmium (Cd) and lead (Pb) in soil-mulberry-silkworm system was assessed. The results showed that bioconcentration factors for Cd and Pb were lower than 1 for all the three mulberry cultivars. Higher translocation factors (TFs) were observed in the levels from branch to leaf, larvae to excrement. The BCFs of Pb in root and silkworm excrement were higher than those in the other parts. Meanwhile, most of Cd accumulated from soils located in the root (48.00-54.40%) and only about 10% was in the leaf. But the Cd and Pb had significant effects on the ratios of cocoon shell with Yuesang 11 under different planting densities. For Yuesang 11 and Qiangsang 1, the Pb percentages were roots > branches > leaves > stems. The rates of ingestion (IR) and digestion (DR) were a little higher than those in the control at first and then decreased gradually with time. The IR reached the lowest values on 8th day while the DR arrived at the highest. Planting mulberry and raising silkworm could be a reasonable method for the utilization of heavy metal contaminated paddy soils.