| With the accelerated development of the chemical industry, mining industry and large amounts of chemical fertilizers and pesticides used in agriculture, heavy metals were inevitably brought into the soil with destroying the ecological environment. The crops absorbed heavy metals into the food chain, thereby endangered human health and even life-threatening. Phytoremediation technology was a method of using plants to clear heavy metals from polluted soil, with excellent characteristics of environmental protection, convenient operation, low cost and no secondary pollution.Kenaf (Hibiscus:Malvaceae) was an annual bast fiber crop, and it was also an bast fiber plant not entering the food chain Which was drought tolerance, alkali resistant, fast-growing, high productive, rich root, anti-stress. The genetic resources center of kenaf had about over1700germplasm resources, which laid a good foundation for selecting materials of using for phytoremediation. Therefore, selecting materials of high endurance, enrichment and yield was significant to remedy heavy metals in contaminated soil. At the same time, it would brought some economic value.In this study, we investigated heavy metal concentrations and bioaccumulation of kenaf growed in south-central farmland of Fujian province. We studied the effects of cadmium on the growth and absorption characteristics of kenaf seedlings by doing hydroponic experiments, and selected varieties which had high resistance and enrichment to cadmium. We did pot culture experiments using the four different varieties which were selected from the hydroponic experiments, studying the characteristics of the accumulation of cadmium between the varieties. Antioxidant system differences in response to cadmium stress were studied between the high resistant varieties and low resistant varieties. By using the proteomics, that responsed to cadmium stress of kenaf leaves and mitigating effect of GSH were studied.1. Heavy metal concentrations and bioaccumulation of kenaf growed in south-central farmland of Fujian province.By the means of field investigation and laboratory analysis, total contents and Bio-available contents of soil heavy metals were analyzed by collecting samples from cultivated soil in four areas of the center and south of Fujian Province, and uptake and accumulation of Cu, Cd, Zn, Cr, Ni and Pb in12sample sites of Fuhong952were also analyzed. The results showed that Cr(187.1mg-kg"1) and Ni(109.5mg·kg-1) in cultivated soil of Zhangpu far exceeded soil environmental quality standards (grade II), were respectively4.5times and7.6times background value of soil elements in Fujian Province, and is respectively2.9times and4.8times of the background value of soil elements in China Though content of Cd was low in four areas, Bio-available contents accounted for more than15%of total content. The bioaccumulation factor of Cd in kenaf were more than1. The highest accumulation contents of shoots.2. Adaptability, accumulation and tolerance evaluation in Cd-stressed kenaf cultivarsCollected53kenaf varieties from different regions and phenotypic characteristics, the concentration of Cd was30μM in hydroponics experiments. The results showed that Cd stress had significant effects on height, root length, pigment, shoot and root biomass of kenaf plants. The higher the concentration, the greater the impact on kenaf growth. The tolerance index was analyzed in clustering based on the membership function, kenaf varieties were divided into three kinds:high-tolerance, middle-tolerance, low-tolerance. In addition, we measured uptake and accumulation of Cd in seedling stage. The tolerance index and total accumulation were analyzed in clustering. Kenaf varieties were further divided into four kinds:high-tolerance and high-accumulation, high-tolerance and low-accumulation, low-tolerance and high-accumulation, low-tolerance and low-accumulation.3. Accumulation of Cd in different kenaf varietiesUsed representative varieties in four types [high-tolerance and high-accumulation (Fuhong991), high-tolerance and low-accumulation(Yue743), low-tolerance and high-accumulation(Fuhonghang992), low-tolerance and low-accumulation(ZM412)] like chapter2as materials, cadmium accumulation kept upward trend in various organs of kenaf with increasing concentration of cadmium, cadmium accumulation in various organs of the high-tolerance:root> stem> leaves> bark, cadmium accumulation in various organs of the low-tolerance:root> leaf> stem>bark. Under unfertilization and fertilization conditions, there were significant differences among shoots accumulation of kenaf varieties, Cd accumulation in shoot of Fuhong991and Fuhonghang992were more than100mg/kg as Cd concentration was120mg/kg, and Fuhong991was up to117.96mg/kg. Fuhonghang992per hectare per year could harvest raw fiber3662.8kg in the soil (Cd,10mg/kg), and remove Cd0.74mg/hm2from polluted soil. Fuhong991per hectare per year can produce raw fiber more than1400kg in the soil (Cd,50mg/kg) and uptake Cd2.58kg/hm2.4. Antioxidant system in response to cadmium stress of KenafAntioxidative enzymes and lipid peroxidation were analysed under control (0.5-strength Hoagland’s nutrient solution) or five levels of cadmium stress (0.5-strength Hoagland’s nutrient solution containing different concentrations of Cd2+) in two kenaf plants (FuHong991and ZM412), the results showed that cadmium stress effected the growth of Kenaf. In different Cd of enzyme(SOD, POD, CAT) activities, there were fluctuation in different degrees of two varieties FuHong991is more tolerant to cadmium than ZM412. The lipid peroxidation was enhanced only in the leaves of Cd-stressed ZM412. These findings indicate that GR might play important roles in Cd-stressed FuHong991and ZM412and that the leaf and root cell membranes of FuHong991have a greater stability than those of ZM412. For the purposes of pollution monitoring of Cd, the GR activity in the roots and leaves may serve as a biomarker of FuHong991, and MDA might serve as biomarker of ZM412.5. Effects Of cadmium stress on kenaf apical cell structureThis study carried out experiments to investigate changes of shape, inter structures and cell microstructures of kenaf roots under Cd stress using obersvation and biomicroscopic technique. With the increase of Cd concentration, in cells of root cortex plasmolysis and the destruction of plasmalemma became more serious, cell organelles disintegrated completely, nucleus membrane finally disappeared leading to nucleolus and nucleoplasm distributing in cytoplasm, dark sediment distributed in cytoplasm, plasmalemma and vessel walls.6. Mitigating effection of cadmium toxicity of Kenaf by adding different concentrations of GSHBy adding different concentrations of GSH, there were significant effects to increase the root length, plant height, shoot fresh weight, dry weight and chlorophyll content of Kenaf seedlings of two varieties. When concentration of GSH was50μM, there was no significant difference in root length between two varieties and the control. There was no difference in plant height, shoot fresh weight, dry weight between Fuhong991and the control. When the concentration of GSH was150μM, the chlorophyll content of leaves basically recovered to the control levels, which showed that GSH played alleviate toxic effect of Cd on Kenaf. When concentration of GSH was50μM, alleviating effect of GSH reached a more ideal threshold. Comprehensive comparative analysis of results showed concentration of50μM could serve as an effective mitigation of Cd.7. The proteomic of Kenaf leaves of different genotypic responsed to Cd stress and alleviating effect of GSHBy using GSH (50μM), the protein expression map and genotypic difference of Cd stress of Kenaf leaves were studied. The results show that the growth of ZM412was significantly inhibited by Cd stress. By software analysis,72protein spots that existed differential expression were identified. We identified50proteins by LC-MS/MS mass spectrometry analysis.8proteins upregulated the expression under Cd stress. Which should be associated with Cd tolerance, and they were involved in photosynthesis, defense and transport. In addition,21proteins responsed to alleviating Cd stress of GSH, these proteins were involved in photosynthesis, protein synthesis, signal transduction, defense, energy and material metabolism. It suggested that GSH played important role in improving tolerance of Kenaf Cd stress. |
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