Nickel and Zn isotopic compositions

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Table of contents

1. Literature review and objectives of the thesis
1.1 Discovery of metal hyperaccumulators and their application
1.2 Hyperaccumulation mechanisms: general concept
1.3 Ni homeostasis in higher plants: current understanding
1.3.1 Ni uptake process
1.3.2 Xylem loading and transport process
1.3.3 Xylem unloading and leaf comparmentation process
1.3.4 Phloem translocation process
1.4 Objectives of the thesis
2. Isotope fractionation of Ni in hyperaccumulators
2.1 Introduction
2.2 Materials and Methods
2.2.1 Plant cultivation and harvest
2.2.2 Analytical methods
2.3 Results
2.3.1 Plant biomass and metal concentrations
2.3.2 Nickel and Zn isotopic compositions.
2.4 Discussion
2.4.1 Ion chelation in media
2.4.2 Ion transport across root cell membrane
2.5 Conclusion
3. Interaction of Ni with other elements in Noccaea caerulescens during the root uptake process
3.1 Introduction
3.2 Materials and methods
3.2.1 Nickel uptake of N. caerulescens under different concentrations of Ni treatments (Expt. 3.1)
3.2.2 Interaction between Ni, Zn, Fe and Co in N. caerulescens (Expt. 3.2)
3.2.3 Gene expression regarding Ni uptake in N. caerulescens (Expt. 3.3)
3.3 Results
3.3.1 Biomass, metal uptake and translocation factor of N. caerulescens in Expt. 3.1
3.3.2 Biomass, metal uptake and translocation factor of N. caerulescens in Expt. 3.2
3.4 Discussion
3.4.1 Interaction between Ni and Zn
3.4.2 Interaction between Ni and Fe
3.4.3 Interaction between Ni and Mn, Cu
3.4.4 Interaction between Ni and Co
3.5 Conclusion
4. Nickel partitioning in leaves of Noccaea caerulescens during xylem and phloem transport
4.1 Introduction
4.2 Materials and methods
4.2.1 N. caerulescens growing in Ni, Sr and Rb solutions (Expt. 4.1)
4.2.2 Foliar application of 61Ni in N. caerulescens (Expt. 4.2)
4.3 Results
4.3.1 Nickel, Rb and Sr accumulation in young and old leaves
4.3.2 Upward and downward movement of Ni in phloem
4.4 Discussion
4.4.1 Nickel partitioning during xylem transport
4.4.2 Nickel partitioning during phloem translocation
4.4.3 Contribution of xylem transport and phloem translocation on Ni accumulation in leaves
4.5 Conclusion
5. Nickel speciation in phloem sap of Noccaea caerulescens
5.1 Introduction
5.2 Materials and methods
5.2.1 Confirmation of the feasibility of the EDTA-stimulated phloem exudation method (Expt. 5.1)
5.2.2 Extraction of phloem exudate from expanding and old leaves of N. caerulescens (Expt. 5.2)
5.3 Results
5.3.1 Nickel, Rb and Sr concentrations in Expt. 5.1
5.3.2 Nickel and Zn concentrations in leaves and phloem exudates of expanding and old leaves in Expt.5.2
5.3.3 Organic compounds in phloem exudate of old leaves
5.4 Discussion
5.4.1 Confirmation of the exudate properties
5.4.2 Nickel enrichment in phloem sap
5.4.3 Nickel speciation in phloem sap
5.5 Conclusion
6. Main conclusions and future scope
6.1 Main findings of the thesis
6.2 Conceptual model for Ni homeostasis in hyperaccumulators
6.3 Future scope
7. References