Cell wall polysaccharides play a vital role in binding with toxic metals such as copper(Cu)ions.However, it is still unclear whether the major binding site of Cu in the cell wall varies with different degrees of Cu stresses.Moreover, the contribution of each cell wall polysaccharide fraction to Cu sequestration with different degrees of Cu stresses also remains to be verified.The distribution of Cu in cell wall polysaccharide fractions of castor(Ricinus communis L.) root was investigated with various Cu concentrations in the hydroponic experiment.The results showed that the hemicellulose1(HC1) fraction fixed 44.9%–67.8% of the total cell wall Cu under Cu stress.In addition, the pectin fraction and hemicelluloses2(HC2) fraction also contributed to the Cu binding in root cell wall,accounting for 11.0%–25.9% and 14.1%–26.6% of the total cell wall Cu under Cu treatments, respectively.When the Cu levels were ≤ 25 μmol/L, pectin and HC2 contributed equally to Cu storage in root cell wall.However, when the Cu level was higher than 25 μmol/L, the ability of the pectin to bind Cu was easy to reach saturation.Much more Cu ions were bound on HC1 and HC2 fractions, and the HC2 played a much more important role in Cu binding than pectin.Combining fourier transform infrared(FT-IR) and twodimensional correlation analysis(2 D-COS) techniques, the hemicellulose components were showed not only to accumulate most of Cu in cell wall, but also respond fastest to Cu stress.
Chao RenYongbo QiGuoyong HuangShiyuan YaoJinwei YouHongqing Hu
[Objective] The article studies the growth and Cu absorption of Ricinus communis L. callus under Cu stress. [Method] CuSO4.5H20 solutions with different Cu concentrations were added to callus subculture medium; callus was inoculated and Cu resistance index of callus was worked out. Cu content in callus was deter- mined with the method of Varian AA240FS. [Result] With the Cu concentration at 60 mg/L, the growth of callus was inhibited, its Cu resistance index was only 33.87%. With the Cu concentration at 40 mg/L, callus was faint yellow in color, and grew rapidly with its Cu resistance index at 61.29%. Such high level resistance could remain the same after six week after continuous subculture. In the 4t week of culture, Cu resistance index in treatments with Cu concentrations at 10, 20, 30, 40 mg/L was higher than that in the 3rd week, and the content of Cu in callus of the treatments was 0.33, 0.54, 1.16, 1.40 mg/g respectively. [Conclusion] Cu con- centration at 40 mg/L in culture medium can be the threshold for selecting Cu re- sistance R. communis callus.
Ricinus communis L. is a new copper hyperaccumulator growing on Tonglushan copper mine in Hubei Province, China. This study aimed to establish a suspension cell line of R. communis L. with stable and rapid growth for further screening of heavy metal-resistant R. communis L. cells and breeding of hyperaccu- mulators. In this study, cell suspension culture conditions were optimized by using orthogonal experimental design with previously induced R. communis L. embyre- genic calluses as experimental materials, to establish the suspension cell line of R. communis L. Under the optimal conditions, growth curves of suspension cells and changes in pH of culture liquid were determined. The results showed that the optimal culture conditions for R. conmmnis L. suspension cell line were ： MS ＋ O. 5 rag/I, 6-BA ＋ O. 2 mg/L NAA ＋ 50 mg/L sucrose ＋ 350 mg/L casein hydrolysate as basic medium, with callus inoculation amount of 2.5 g/50 ml, dark culture at （26 ±2） ℃ with shaking at 110 r/min. Under these conditions, increment of fresh weight and dry weight ofR. commun/s L. suspension cells reached the maximum of 4.56 g/（50 ml 14 d） and 0.49 g/（50 ml 16 d）, respectively. Growth curves of R. communis L. suspension cells were basically in ＂S＂ shape. Each culture cycle lasted 16 d, and the rapid growth stage was from the 6th d to the 14th d. In a culture cycle, pH of the culture liquid declined first and then increased to the maximum and stabilized gradually.
