Wound-induced vascular occlusions in tissues of the reed Phragmites australis: their development and chemical nature

This work focuses on the development of vascular occlusions, which are gels resealing the wounded vascular systems of injured organs, in the common reed Phragmites australis. Their formation seems to be crucial in keeping the internal environment of the plant stable. Histochemical tests, combined with an extraction series, were used to follow changes in the chemical nature of gels during their development. It was found that the first gel material was secreted by living cells in the vicinity of the incision within 1 or 2 d after wounding. Early gels were colourless and mainly composed of acidic polysaccharides interlinked by Ca2+ bridges. The properties of the gel material gradually changed during maturation. The matrix of polysaccharides in the early gels was later modified and interlinked by other components, resulting in a highly resistant material. Structural proteins were identified as the principal interlocking components of the material, and were responsible for its high resistance.