Adsorption of Cd(II) by rhizosphere and non-rhizosphere soil originating from mulberry field under laboratory condition.

In this study, the adsorption behavior of Cd ions by rhizosphere soil (RS) and non-rhizosphere soil (NS) originated from mulberry field was investigated. The Langmuir, Freundlich and the Dubinin-Radushkevich (D-R) equations were used to evaluate the type and efficiency of Cd adsorption. The RS was characterized by lower pH but the higher content of soil organic matter and cation exchange capacity (CEC) as compared to NS. Also, the maximum adsorption of Cd2+ for RS (5.87 mg/g) was slightly bigger than that for NS (5.36 mg/g). In Freundlich isotherm, the Kf of the adsorption of Cd2+ to surface of the RS components was higher than that of the NS, indicating stronger attraction between Cd2+ and components of the RS. According to the D-R model, the adsorption of Cd2+ by both soils was dominated by ion exchange phenomena. These results indicated that mulberry roots modified physical and chemical properties of the RS under field conditions, which also affected the Cd sorption efficiency by soil components during laboratory experiments. Current knowledge of the Cd2+ sorption processes in the rhizosphere of mulberry may be important if these trees are planted for use in phytoremediation of Cd contaminated soils.

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.

Variations in the levels of mulberroside A, oxyresveratrol, and resveratrol in mulberries in different seasons and during growth.

This study aimed to investigate the composition of three major stilbenes (mulberroside A, oxyresveratrol, and resveratrol) in different portions of mulberries collected in different seasons and their change molds during growth by high-performance liquid chromatography. Mulberroside A levels were the highest in the bark and roots of Morus atropurpurea Roxb, Morus alba Linn, and Morus latifolia Poir. Oxyresveratrol levels were the highest in roots and stem. Both of these high levels were in September. The amount of resveratrol was very low in all samples. In the stem, Morus latifolia Poir contained more mulberroside A than the other two mulberries. Mulberroside A was not detected in the leaves of the three mulberries. In Morus atropurpurea Roxb seedlings, the root tended to contain more of the three stilbenes than leaves. The temporal peaks of resveratrol were always ahead of those for oxyresveratrol. The levels of the stilbenes varied in different portions of the varieties of mulberries collected in different season and in the seedlings of Morus atropurpurea Roxb.

[Comparative and correlational studies on contents of stilbenes in different portions of mulberry].

OBJECTIVE: To compare the contents of stilbenes in different parts and axial root bark of mulberry, and study their correlation. METHOD: The contents of 3 major stilbenes, mulberroside A, oxyresveratrol, and resveratrol in different parts of mulberry were determined by HPLC. The correlation and regression analysis between the contents of stilbenes in the different parts and axial root bark was carried out. RESULT: The contents of stilbenes in most different parts of mulberry showed significant correlation. Between the contents of stilbenes in the different parts and axial root bark, oxyresveratrol showed significant correlation among all different parts, resveratrol showed significant correlation except in spinal cord of annual branch, mulberroside A showed significant correlation between bark of annual branch, lateral root and axial root bark. The results of the correlation and regression analysis indicated that the contents of mulberroside A, oxyresveratrol, resveratrol in different parts and axial root bark were significant positively correlated. CONCLUSION: The contents of stilbenes are significant correlation distributed in different parts and axial root bark of mulberry. The contents of stilbenes in different parts could be used to estimate the content of the axial root bark. The result could be useful for breeding and preserving excellent germplasm at the system breed process for mulberry of rich in stilbenes.

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.

Application of economic plant for remediation of cadmium contaminated soils: Three mulberry (Moms alba L.) varieties cultivated in two polluted fields.

In order to study the role of mulberry (Moms alba L) as an economic crop for remediation of cadmium (Cd) contaminated soil, the transport of Cd from mulberry to silkworm were investigated. Three varieties of mulberry (Yuesang-11, Nongsang-14, and Qiangsang-1) with three planting densities were cultivated in two heavy metal-contaminated fields named Dongkou in Shaoyang city and Linxiang in Yueyang city in Hunan province respectively. The both field soils were contaminated by heavy metals, especially by Cd. The potential risks of heavy metals in Linxiang's soil were higher than those in Dongkou's because of higher concentrations of Cd. Since the promotion of Cd concentrations in aerial parts (stem, branch and leaf) resulted from the increase of planting density, the method of high planting density is beneficial to improve the efficiency of the remediation of Cd contaminated soil. The percentages of average Cd contents of mulberry in Dongkou accounted for 44%, 20%, 18% and 16% in roots, stems, branches and leaves respectively, while the Cd contents were 38%, 27%, 19% and 16% distributed in roots, stems, branches and leaves respectively. Mulberry leaves from contaminated soils was applied in food source of silkworms in this study. Although there is Cd uptake occurred in silkworm growth and its products (cocoons and chrysalis), Cd contents in cocoons are lower than the national standard (100 µg*kg-1) for textile industry of China. Therefore, mulberry can be regarded as an economical crop to control soil contamination with Cd.