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Table of contents
General introduction
I. The maize plant
a) Back to origins
b) Anatomy of the maize plant
c) Maize crop production and valorization
1. The digestibility of corn silage, degradability of the walls seen from the side of the cow
i. In vivo or in vitro estimation of digestibility.
ii. Criteria for registration in the French official catalog and impact on varietal selection
2. Bioethanol production from maize crop residues, degradability seen from the EZ process side
i. Biomass and 2nd generation biorefineries
ii. Pretreatment of lignocellulosic biomass for bioethanol production
1- Chemical pretreatments
2- Physicochemical pretreatments
II. Cell wall in grasses
a) Structure
b) Polysaccharidic compounds
1. Cellulose
2. Hemicelluloses
3. Pectins
c) Phenolic compounds
1. Lignins
i. Composition of the lignins
ii. Impacts of the modifications of the lignin biosynthesis pathway
2. p-hydroxycinnamic acids
i. Ferulic acids
ii. p-coumaric acids
III. Distribution of the lignification within the maize stem tissues
a) Tissue anatomy in maize
b) Methods to investigate the tissue specificities
1. Imaging techniques
i. Darkfield microscopy
ii. Brightfield microscopy
2. Conclusion
IV. Cell wall establishment during maize stem development
a) Genetic variation for internode elongation, cross section surface and cell size within the three genotypes throughout internode development
b) The main differences for internode elongation and cell wall phenolic composition were positioned at young stages, before silking
c) Different developmental patterns were observed for lignin content, composition, structure and distribution
1. Evolution of lignin content all along the internode development
2. Evolution of lignin structure and composition all along development
3. Evolution of lignin distribution at tissue level all along the internode development
d) Throughout internode growth different developmental patterns were observed for phydroxycinnamic acids accumulation
1. Evolution of esterified p-coumaric acid content all along internode development
e) Esterified ferulic acids were deposed all along plant development but used to anchor lignification only at early stages
f) Combination of the biochemical and histological findings to propose a model of spatiotemporal cell wall development
V. Relationships between cell wall degradability and 1- biochemical cell wall components and 2- the distribution of lignification
a) Impact of the cell wall biochemistry on the cell wall degradability
b) Impact of the distribution of the lignification on cell wall degradability
VI. Impact of water stress on cell wall composition and on lignification distribution
VII. Genetic determinism of the cell wall traits under different watering conditions
a) QTLs of cell wall components
b) QTLs of tissue distribution
c) QTLs under different watering conditions
VIII. Objectives of my PhD
Chapter 1 Introduction
Material and Methods
Histological analyses
(Accepted Article) Histological quantification of maize stem sections from FASGA-stained images
Dedicated NIRS predictive equations establishment and NIRS predictions of cell wall related traits in maize internodes
I. (Accepted article) Impact of the water deficit on the biochemical composition of the cell wall, the lignification distribution with the tissues and the degradability of the cell wall of maize stems
II. F2bm3 does not respond histologically or biochemically to water deficit
a) Cell wall composition of F2bm3 internode and response to water deficit
1. F2bm3 and the NIRS predictions
2. Estimations of the F2bm3 cell wall components values
3. Biochemical relationships and response to water deficit
b) Histological profiles of F2bm3 and response to water deficit
Conclusion
Chapter 2 Introduction
Material and Methods
Plant materials and field experiments
NIRS predictive equations construction and NIRS predictions
I. Results
a) 2 years of field experiments declined in 4 irrigation conditions due to different environmental context
b) Phenotypic variations
1. The parental inbred lines and their characteristics under different irrigation condition
2. Variations of biochemical and histological traits among the recombinant inbred lines showed transgression and allowed to obtain expected correlations between traits
c) Genetic determinism of histological traits under different irrigation conditions.
d) QTLs involved in the variation of biochemical traits and co-localizations with QTLs involved in the variation of histological traits
e) Genetic determinism for biochemical cell wall traits of the whole plant without ears matches with the genetic determinism for biochemical cell wall traits of the internode in maize and with
II. (Submitted article) Water deficit responsive QTLs for cell wall degradability and composition traits in maize at silage stage
Conclusion
Chapter 3 Introduction
I. Variation of cell wall biochemistry of the internode carrying the main ear reflects the variations of cell wall biochemistry of the whole plant without ear
Material and Methods
Results and discussion
II. The histology of the internode carrying the main ear reflects the mean all the internodes of the stem.
Material and Methods
a) Histological pattern of the internode carrying the main ear reflects the average histological pattern of all the internodes of a maize stem.
b) Histological variations of the internode carrying the main ear partially reflect variation of the biochemistry of the whole plant without ears.
Conclusion
Chapter 4 What bricks do we bring to the cell wall degradability understanding?
a) Development and probation of high-throughput tools
b) The understanding of cell wall degradability
c) Impact of water deficit on the biomass quality
d) From the internode to the whole plant
II. All these results may be discussed further
a) Going further in the improvement of the high-throughput tools
b) Choice of the plant material and and monitoring of the water deficit conditions to address the PhD questions
c) Relationships between cell wall degradability and lignification at different scales
1. Targeting the general cell wall composition within the plant
2. Targeting tissues specificities within the plant
d) Impact of the water deficit on the lignification at different scales
III. Perspectives
References
