| Acknowledgement | 第11-17页 |
| Abstract | 第17-18页 |
| 摘要 | 第19-23页 |
| Chapter 1 Literature review | 第23-40页 |
| 1.1 Influence of N nutrition on plant growth and development | 第23-24页 |
| 1.2 N metabolism in plants | 第24-26页 |
| 1.3 Factors affecting nitrogen absorption and assimilation | 第26-31页 |
| 1.3.1 Nitrogen level and form | 第26页 |
| 1.3.2 Root system | 第26-28页 |
| 1.3.3 Key enzymes | 第28-31页 |
| (1) Nitrate reductase | 第28-29页 |
| (2) Glutamine synthetase | 第29-30页 |
| (3) Glutamate synthase | 第30页 |
| (4) Glutamate dehydrogenase | 第30-31页 |
| 1.4 Genetic improvement of nitrogen use efficiency | 第31-35页 |
| 1.4.1 Importance of NUE | 第31-32页 |
| 1.4.2 Genetic controlling of nitrogen use efficiency | 第32-34页 |
| 1.4.3 Genetic improvement | 第34-35页 |
| 1.5 Advance in study on N metabolism and NUE in Barley | 第35-38页 |
| 1.5.1 Barley production and biological properties | 第36-37页 |
| 1.5.2 Genetic variation of N metabolism and NUE | 第37页 |
| 1.5.3 Tibetan wild barley and its potential in improvement of NUE in barley | 第37-38页 |
| 1.6 The objectives of the current research | 第38-40页 |
| Chapter 2 Growth and physiological characterization of low nitrogen responses in Tibetan wild andcultivated barleys | 第40-49页 |
| 2.1 Materials and methods | 第41-43页 |
| 2.1.1 Gas exchange parameters | 第41页 |
| 2.1.2 Antioxidant enzyme activity | 第41-42页 |
| 2.1.3 Measurement of N concentration | 第42页 |
| 2.1.4 Calculation and statistical analysis | 第42-43页 |
| 2.2 Results and analysis | 第43-47页 |
| 2.2.1 Growth characters | 第43页 |
| 2.2.2 Photosynthetic parameters | 第43-44页 |
| 2.2.3 Shoot and Root N concentration, accumulation and NUE | 第44-45页 |
| 2.2.4 Antioxidant enzyme activity | 第45-47页 |
| 2.3 Discussion | 第47-48页 |
| 2.4 Conclusion | 第48-49页 |
| Chapter 3 Nitrogen metabolism related enzyme activities, cell ultrastructure and nutrient contents asaffected by N level and barley genotype | 第49-64页 |
| 3.1 Materials and methods | 第51-54页 |
| 3.1.1 Plant materials, growth conditions and treatments | 第51页 |
| 3.1.2 Examination of ultrastructure | 第51-52页 |
| 3.1.3 Determination of photosynthetic pigments and leaf area | 第52页 |
| 3.1.4 Determination of maximum photochemical efficiency | 第52页 |
| 3.1.5 Determination of enzyme activities | 第52-53页 |
| 3.1.6 Element analysis | 第53-54页 |
| 3.1.7 Statistical analysis | 第54页 |
| 3.2 Results | 第54-59页 |
| 3.2.1 Ultrastructural changes | 第54-56页 |
| 3.2.2 Leaf area, chlorophyll content and maximal photochemical efficiency (Fv/Fm) | 第56页 |
| 3.2.3 Nutrient contents in plant tissues | 第56-59页 |
| 3.2.4 Activities of the N metabolism associated enzymes | 第59页 |
| 3.3 Discussion | 第59-63页 |
| 3.4 Conclusion | 第63-64页 |
| Chapter 4 Expression of nitrogen metabolism genes in wild and cultivated barley in response to lownitrogen supply | 第64-78页 |
| 4.1 Material and Methods | 第66-68页 |
| 4.1.1 Plant materials, growth conditions and treatments | 第66-67页 |
| 4.1.2 Measurement of N concentration | 第67页 |
| 4.1.3 Measurement of soluble protein | 第67页 |
| 4.1.4 Chlorophyll Content | 第67页 |
| 4.1.5 qRT-PCR and gene expression analysis | 第67-68页 |
| 4.1.6 Statistical analysis | 第68页 |
| 4.2 Results and analysis | 第68-75页 |
| 4.2.1 N concentration in shoots and roots | 第68-69页 |
| 4.2.2 Chlorophyll content and soluble proteins | 第69-70页 |
| 4.2.3 Tillers per plant | 第70页 |
| 4.2.4 Genotypic difference of GS1, GS2 and NRT2.1 expression levels in response to N level | 第70-75页 |
| 4.3 Discussion | 第75-78页 |
| Chapter 5 Major findings and future prospects | 第78-81页 |
| References | 第81-99页 |
