Surface d'une feuille d'Arabette des dames observée en cryo-microscopie électronique à balayage

Leaf surface of the mouse-ear cress Arabidopsis thaliana, observed using a scanning electron microscope after chemical fixation. The images have been manually coloured using the Gimp2 software package. The leaf surface is shown in green. A stoma can be seen in the centre of the photo. Epiphytic bacteria are naturally present on the surface of the leaf (in red). These examinations were carried out as part of research to obtain a full understanding of the mechanisms through which plants (cauliflower or Arabidopsis thaliana) are infected by the pathogenic bacterium Xanthomonas campestris. The use of cryo-preparation with scanning electron microscopy makes it possible to keep the biological object in its original state (frozen, hydrated), reducing the potential artefacts associated with the chemical preparation of samples. In this way, the detailed anatomy of structures has been described for various plant species, whether infected or not by Xanthomonas. Initial results have helped clarify the structure of the hydathodes located on the edge of the leaves, and demonstrated that the hydathode pores (which resemble stomata) are the points at which the Xanthomonas bacterium infects the leaves. Based on these conclusions, further research is being done into controlling infection at a molecular level.