Cadmium in soils

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Table of contents

CHAPTER 1 GENERAL INTRODUCTION
1.1 CADMIUM AND HUMAN
1.1.1 Cadmium poisoning
1.1.2 Anthropogenic cadmium contamination
1.1.3 Cadmium in soils
1.1.4 Cadmium in foodstuffs
1.2 DURUM WHEAT
1.2.1 The plant of durum wheat
1.2.2 Durum wheat production and consumption
1.2.3 Cadmium in durum wheat
1.3 PHYSIOLOGY OF CADMIUM ALLOCATION TO GRAINS
1.3.1 Root uptake and short-distance transport to the stele
1.3.2 Long-distance transport and partitioning
1.3.3 Remobilization from vegetative organs to developing grains
1.3.4 Loading and storage in grains
1.4 WAYS TO MINIMIZE THE LEVEL OF CADMIUM IN DURUM WHEAT-BASED FOODS
1.4.1 Agriculture practices
1.4.2 Post-harvest practices
1.5 STRUCTURE AND AIMS OF THE THESIS
CHAPTER 2 VARIABILITY IN GRAIN CADMIUM CONCENTRATION AMONG DURUM WHEAT CULTIVARS: IMPACT OF ABOVEGROUND BIOMASS PARTITIONING
ABSTRACT
2.1 INTRODUCTION
2.2 MATERIALS AND METHODS
2.2.1 Design of the experiment
2.2.2 Plant culture
2.2.3 Plant sampling and analyses
2.2.4 Determination of the root cation exchange capacity
2.2.5 Modelling between-cultivar variability in grain cadmium
2.2.6 Data processing
2.3 RESULTS
2.3.1 Plant growth, biomass partitioning and grain yield
2.3.2 Grain cadmium
2.3.3 Plant cadmium
2.3.4 Predictive model for grain cadmium concentration
2.3.5 Correlations between grain cadmium and other grain characteristics
2.4 DISCUSSION
2.4.1 Variability in grain cadmium within French lines was not explained by uptake and root sequestration of cadmium
2.4.2 Impact of the grain yield
2.4.3 Impact of the aboveground partitioning of biomass
2.4.4 Co-accumulation of cadmium with manganese, phosphorus and zinc in the grain
2.5 CONCLUSIONS
2.6 ACKNOWLEDGMENTS
2.7 SUPPLEMENTARY MATERIAL
CHAPTER 3 CONTRIBUTION OF REMOBILIZATION TO THE LOADING OF CADMIUM IN DURUM WHEAT GRAINS: IMPACT OF POST-ANTHESIS NITROGEN SUPPLY
ABSTRACT
3.1 INTRODUCTION
3.2 MATERIALS AND METHODS
3.2.1 Experimental design
3.2.2 Plant culture
3.2.3 Cadmium isotope labeling
3.2.4 Plant sampling and analysis
3.2.5 Data analysis
3.2.6 Statistical analysis
3.3 RESULTS
3.3.1 Plant growth
3.3.2 Grain characteristics
3.3.3 Concentrations of nitrogen and cadmium in vegetative organs
3.3.4 Post-anthesis uptake and apparent remobilization of nitrogen
3.3.5 Post-anthesis uptake and remobilization of cadmium
3.4 DISCUSSION
3.4.1 Contribution of cadmium remobilization under standard nitrogen supply
3.4.2 Source of cadmium remobilization
3.4.3 Cadmium remobilization as a senescent-independent process?
3.4.4 Impact of post-anthesis nitrogen-deprivation
3.4.5 Between-cultivar differences
3.5 CONCLUSION
3.6 ACKNOWLEDGMENTS
3.7 SUPPLEMENTARY MATERIAL
CHAPTER 4 ALLOCATION OF CADMIUM TO GRAINS OF DURUM WHEAT EXPOSED TO 5 OR 100 NM CADMIUM IN HYDROPONICS
ABSTRACT
4.1 INTRODUCTION
4.2 METHODS AND MATERIALS
4.2.1 Experimental design
4.2.2 Plant culture
4.2.3 Cadmium isotope labeling
4.2.4 Plant sampling and analysis
4.2.5 Cadmium accumulation in the first node and in the peduncle
4.2.6 Data processing
4.2.7 Statistical analysis
4.3 RESULTS
4.3.1 Plant growth
4.3.2 Grain characteristics
4.3.3 Cadmium accumulation level in plant tissues
4.3.4 Pre-anthesis uptake and partitioning of cadmium
4.3.5 Post-anthesis uptake and partitioning of cadmium
4.3.6 Cadmium remobilization
4.3.7 Relationships between the grain maturation rate and the dynamics of cadmium post-anthesis
4.4 DISCUSSION
4.4.1 Effect of cadmium exposure on plant growth
4.4.2 Buffer ability of durum wheat in the change of exposure level to cadmium
4.4.3 Effect of earlier maturing of grains
4.5 CONCLUSION
4.6 ACKNOWLEDGMENTS
4.7 SUPPLEMENTARY MATERIAL
CHAPTER 5 IMAGING OF CADMIUM DISTRIBUTION IN MATURE DURUM WHEAT GRAINS USING LASER ABLATION-ICP-MS
ABSTRACT
5.1 INTRODUCTION
5.2 MATERIALS AND METHODS
5.2.1 Grain production
5.2.2 Cryomicrotomy
5.2.3 LA-ICP-MS imaging
5.2.4 Grain dissection and analysis
5.2.5 Budget of element partitioning between grain parts from dissection results
5.2.6 Statistical analysis
5.3 RESULTS
5.3.1 LA-ICP-MS imaging of elements in durum wheat grains
5.3.2 Concentrations of elements in dissected grain parts
5.3.3 Loss of biomass and elements by removing grain parts
5.4 DISCUSSION
5.4.1 Localization of cadmium and essential elements in durum wheat grain assessed by LA-ICP-MS and grain dissection
5.4.2 Localization of cadmium and essential elements in durum wheat grains with respect to the mechanisms of grain filling
5.4.3 Interest of post-harvest treatment for lowering the level of cadmium in durum wheat-derived products
5.5 CONCLUSIONS
5.6 ACKNOWLEDGMENTS
5.7 SUPPLEMENTARY MATERIAL
CHAPTER 6 GENERAL DISCUSSION
6.1 LEAVES ARE CADMIUM SINKS IN COMPETITION WITH DEVELOPING GRAINS
6.2 HALF OF GRAIN CADMIUM ORIGINATES FROM CADMIUM TAKEN UP DURING GRAIN FILLING WHILE THE OTHER HALF FROM CADMIUM REMOBILIZED
6.3 DURUM WHEAT IS SENSITIVE TO CHANGES IN THE LEVEL OF CADMIUM EXPOSURE IN THE RANGE OF THOSE ENCOUNTERED IN AGRICULTURAL CONTEXT
6.4 TOWARDS THE EFFICIENCY AND THE SELECTIVITY OF GRAIN MILLING PROCESS TO LOWER THE CADMIUM CONCENTRATION IN DURUM WHEAT-BASED PRODUCTS
6.5 POSSIBLE LIMITATIONS OF THE THESIS
CHAPTER 7 GENERAL CONCLUSION AND PERSPECTIVES
7.1 CONCLUSIONS
7.2 SUGGESTIONS
7.3 WHAT WOULD NEED TO BE DONE FURTHER?
REFERENCES