The vascular tissues in Arabidopsis thaliana floral stem: High spatial resolution using Synchrotron infrared, Raman and deep UV spectroscopy
Résumé
In higher plants, a network of vascular tissues (the phloem and the xylem), which supply water, minerals and other nutrients, connects the different organs and provides mechanical support for the aerial organs. The xylem and the phloem are two highly specialized conductive tissues. The cell wall surrounding the vascular cells is reinforced by a complex matrix of sugar-derived compounds (i.e.: cellulose, hemicellulose, pectins) and lignin, whose compositions depend on the cell type and developmental stage. For example low lignin and high hemicellulose content characterize phloem cells, while lignin and xylans are enriched in xylem cells. The supply and synthesis of the cell wall precursors take place in specialized parenchyma and fibre cells, which are responsible of the thickening of the associated conductive cell walls. As a consequence phloem and xylem cells represent a sink for consumption and sequestration of carbohydrates, with a competitive allocation of carbon pools between lignin and cellulosic compounds, which leads to a negative correlation between biomass production and lignin content. To improve our knowledge on these processes, we focus on the carbohydrate components deposited during cell wall formation of phloem and xylem cells using the Arabidopsis thaliana floral stem as a model for carbon allocation. Our investigations, by label-free Synchrotron FT-IR, Raman and deep ultra violet microspectroscopies, of the cell wall composition and the cytosolic content of the different xylem and phloem cell types will be presented, using the floral stem of both Arabidopsis wild-type plants and mutants affected in sugar homeostasis.