| List of Abbreviations | 第17-18页 |
| ABSTRACT | 第18-20页 |
| 摘要 | 第21-23页 |
| CHAPTER Ⅰ Research background and review of literature | 第23-55页 |
| 1.1 Research background | 第23-24页 |
| 1.2 Physical and chemical properties of Ni | 第24-25页 |
| 1.3 Total reserves, production and uses of Ni worldwide | 第25-26页 |
| 1.4 Sources of Ni in environment | 第26-27页 |
| 1.5 Occurrence of Ni in environment | 第27-32页 |
| 1.5.1 Ni in soils and sediments | 第28-29页 |
| 1.5.2 Ni in atmosphere | 第29-31页 |
| 1.5.3 Ni contents in various food products | 第31-32页 |
| 1.6 Potential threats of Ni toxicity to aquatic organisms, animals and Humans | 第32-35页 |
| 1.6.1 Effects of Ni toxicity in humans | 第32-33页 |
| 1.6.2 Toxic effects of Ni on animals | 第33-34页 |
| 1.6.3 Toxic effects of Ni on aquatic organisms | 第34-35页 |
| 1.7 Functions and toxicity of Ni in plants | 第35-41页 |
| 1.7.1 Uptake of Ni in plants | 第36-38页 |
| 1.7.2 Transport and distribution of Ni in plants | 第38-40页 |
| 1.7.3 Essentiality of Nickel in Plants | 第40-41页 |
| 1.8 Ni toxicity in plants | 第41-43页 |
| 1.8.1 Seed germination, plant growth and crop yield | 第41-42页 |
| 1.8.2 Photosynthesis and gas exchanges parameters | 第42-43页 |
| 1.9 Toxicity mechanisms of Ni in plants | 第43-46页 |
| 1.9.1 Interference with other essential metal ions | 第43-44页 |
| 1.9.2 Induction of oxidative stress | 第44-46页 |
| 1.10 Nitric oxide | 第46-48页 |
| 1.10.1 Nitric oxide biosynthesis in plants | 第47-48页 |
| 1.10.2 Nitric oxide: an effective weapon of the plant | 第48页 |
| 1.11 Hydrogen sulfide | 第48-52页 |
| 1.11.1 Properties of hydrogen sulfide | 第49页 |
| 1.11.2 Hydrogen sulfide biosynthesis in plants | 第49-50页 |
| 1.11.3 H_2S signaling triggered by abiotic stresses | 第50-52页 |
| 1.11.4 Positive effect of H_2S on plant growth under abiotic stresses | 第52页 |
| 1.12 Research gap | 第52-53页 |
| 1.13 Specific objectives | 第53-55页 |
| CHAPTER Ⅱ Nickel stressed responses of rice in Ni subcellular distribution, antioxidant production and osmolyte accumulation | 第55-74页 |
| 2.1 Introduction | 第55-56页 |
| 2.2 Materials and methods | 第56-59页 |
| 2.2.1 Plant material and growth conditions | 第56-57页 |
| 2.2.2 Determination of growth parameters | 第57页 |
| 2.2.3 Quantification of photosynthetic pigments | 第57页 |
| 2.2.4 Determination of Ni content | 第57页 |
| 2.2.5 Determination of Ni in subcellular fractions | 第57-58页 |
| 2.2.6 Estimation of level of hydrogen peroxide (H_2O2) and malondialdehyde (MDA) content | 第58页 |
| 2.2.7 Extraction and assay of antioxidant enzymes | 第58页 |
| 2.2.8 Extraction and assay of non-enzymatic antioxidant, ascorbate and glutathione | 第58-59页 |
| 2.2.9 Quantification of osmotic regulators | 第59页 |
| 2.3 Statistical analysis | 第59页 |
| 2.4 Results | 第59-69页 |
| 2.4.1 Ni uptake and subcellular distribution | 第59-62页 |
| 2.4.2 Ni stress increased H_2O2 levels and MDA contents | 第62-63页 |
| 2.4.3 Effect of Ni stress on enzymatic and non-enzymatic antioxidant | 第63-66页 |
| 2.4.4 Effect of Ni stress on osmotic regulators | 第66-68页 |
| 2.4.5 Effect of Ni stress on photosynthetic pigments | 第68页 |
| 2.4.6 Effect of Ni stress on rice growth and biomass | 第68-69页 |
| 2.5 Discussion | 第69-73页 |
| 2.6 Conclusion | 第73-74页 |
| CHAPTER Ⅲ Nickel toxicity affects nitrogen metabolism in rice (Oryza sativa L.) plants | 第74-87页 |
| 3.1 Introduction | 第74-76页 |
| 3.2 Materials and methods | 第76-77页 |
| 3.2.1 Plant material and growth conditions | 第76页 |
| 3.2.2 Determination of plant growth | 第76页 |
| 3.2.3 Quantification of photosynthetic pigments | 第76页 |
| 3.2.4 Quantification of Ni content | 第76-77页 |
| 3.2.5 Determination of NO3– and NH_4~+ contents | 第77页 |
| 3.2.6 Determination of N metabolism related enzyme activities | 第77页 |
| 3.3 Statistical analysis | 第77-78页 |
| 3.4 Results | 第78-83页 |
| 3.4.1 Ni-induced toxicity symptoms and Ni contents in rice plants | 第78-79页 |
| 3.4.2 Impact of Ni stress on plant growth, biomass and photosynthetic pigments | 第79-80页 |
| 3.4.3 Effects of Ni stress on NO3– and NH_4~+ contents | 第80-81页 |
| 3.4.4 Effects of Ni stress on enzymes involved in N metabolism | 第81-83页 |
| 3.5 Discussion | 第83-85页 |
| 3.6 Conclusion | 第85-87页 |
| CHAPTER Ⅳ Nitric oxide induces rice tolerance to excessive nickel by regulating nickel uptake, reactive oxygen species detoxification and defense-related gene expression | 第87-112页 |
| 4.1 Introduction | 第87-89页 |
| 4.2 Materials and methods | 第89-92页 |
| 4.2.1 Plant material and growth conditions | 第89页 |
| 4.2.2 Nitric oxide and Ni treatments | 第89-90页 |
| 4.2.3 Growth parameters | 第90页 |
| 4.2.4 Measurement of Ni content and NO level in roots and shoots | 第90-91页 |
| 4.2.5 Determination of photosynthetic pigments, soluble protein and proline contents | 第91页 |
| 4.2.6 Determination of levels of H_2O2, MDA and electrolyte leakage | 第91页 |
| 4.2.7 Extraction and assay of antioxidant enzymes | 第91页 |
| 4.2.8 Extraction and estimation of total ascorbic acid (As A) and glutathione (GSH) contents | 第91-92页 |
| 4.2.9 Total RNA extraction, c DNA synthesis, and quantitative real-time polymerase chain reaction (q RT-PCR) analysis | 第92页 |
| 4.3 Statistical analysis | 第92-93页 |
| 4.4 Results | 第93-107页 |
| 4.4.1 NO, rather than other derivatives, contributed to the alleviation of rice seedlings under Ni stress | 第93-95页 |
| 4.4.2 Effect of NO scavenger on NO-induced Ni tolerance in rice seedlings | 第95-97页 |
| 4.4.3 Exogenous NO suppresses Ni uptake to overcome Ni toxicity | 第97页 |
| 4.4.4 NO mitigates the Ni-Induced inhibition of rice seedling growth | 第97-99页 |
| 4.4.5 NO enhances photosynthetic pigments under Ni stress | 第99页 |
| 4.4.6 NO increases the accumulation of soluble protein and proline content under Ni stress | 第99-101页 |
| 4.4.7 NO maintains the membrane integrity by suppressing the H_2O_2, MDA content and EL under-Ni stress | 第101-103页 |
| 4.4.8 NO efficiently upregulates the activities of enzymatic and non-enzymatic antioxidant to counteract oxidative stress | 第103-105页 |
| 4.4.9 Impact of NO and Ni on genes expression | 第105-107页 |
| 4.5 Discussion | 第107-110页 |
| 4.6 Conclusion | 第110-112页 |
| CHAPTER Ⅴ Hydrogen sulfide enhances rice tolerance to nickel through prevention of chloroplast damage and improvement of nitrogen metabolism under excessive nickel | 第112-138页 |
| 5.1 Introduction | 第112-114页 |
| 5.2 Materials and methods | 第114-119页 |
| 5.2.1 Plant material, growth conditions and treatments | 第114-115页 |
| 5.2.2 Determination of plant growth | 第115页 |
| 5.2.3 Determination of Ni content | 第115页 |
| 5.2.4 Determination of H_2S content | 第115页 |
| 5.2.5 Gas exchange measurements and photosynthetic pigments | 第115-116页 |
| 5.2.6 Transmission electron microscopy | 第116页 |
| 5.2.7 Extraction and assay of antioxidant enzymes | 第116页 |
| 5.2.8 Extraction and estimation of total ascorbic acid (As A) and glutathione (GSH) contents | 第116-117页 |
| 5.2.9 Determination of NO3– and NH_4~+ contents | 第117页 |
| 5.2.10 Determination of N metabolism-related enzyme activities | 第117页 |
| 5.2.11 Total RNA extraction, c DNA synthesis, and quantitative real-time polymerase chain reaction (q RT-PCR) analysis | 第117-119页 |
| 5.3 Statistical analysis | 第119页 |
| 5.4 Results | 第119-133页 |
| 5.4.1 H_2S, rather than other derivatives, contributed to the alleviation of rice seedlings under Ni stress | 第119页 |
| 5.4.2 Effect of H_2S scavenger and its biosynthesis inhibitor on H_2S-induced Ni tolerance in rice seedlings | 第119-122页 |
| 5.4.3 H_2S suppresses Ni uptake to overcome Ni toxicity | 第122页 |
| 5.4.4 H_2S improves plant growth under Ni stress | 第122页 |
| 5.4.5 H_2S maintains gas exchange parameters in response to Ni stress | 第122-125页 |
| 5.4.6 H_2S protects photosynthetic pigments | 第125页 |
| 5.4.7 H_2S protects the ultrastructure of chloroplasts from Ni-induced damage | 第125-126页 |
| 5.4.8 H_2S maintains the membrane integrity by suppressing the H_2O_2 and MDA content under Ni stress | 第126-127页 |
| 5.4.9 H_2S efficiently upregulates the activities of antioxidant enzymes and total As A and GSH contents | 第127-129页 |
| 5.4.10 H_2S balances NO_3~- and NH_4~+ contents in rice leaves | 第129页 |
| 5.4.11 H_2S boosts the activities of N metabolism related enzymes | 第129-131页 |
| 5.4.12 Transcriptional regulation of genes involved in N uptake and metabolism | 第131-133页 |
| 5.5 Discussion | 第133-136页 |
| 5.6 Conclusion | 第136-138页 |
| CHAPTER Ⅵ Conclusions and future suggestions | 第138-141页 |
| 6.1 General conclusions | 第138-139页 |
| 6.2 Future suggestions | 第139-141页 |
| References | 第141-169页 |
| List of Publication | 第169-170页 |
| ACKNOWLEDGMENT | 第170-173页 |
