Congo red inhibition of wall regeneration by physcomitrella protoplasts: Structural aspects

The effect of the dye congo red on the formation of a fibrous wall at the surface of protoplasts of the moss Physcomitrella patens has been studied by electron microscopy. Concentrations of the dye above 10mg 1⁻¹ caused total inhibition of fibre formation judged by scanning electron microscopy. At lower concentrations, the presence of the dye results in abnormal walls being formed. These show short atypical fibres of variable thickness. Negative staining shows the presence amongst such fibres of amorphous material. When protoplasts are incubated with media containing congo red for 4hr at 23°C, about half the dye can be recovered as a pellet following high speed centrifugation of the medium. This proportion is reduced at 0°C and also by the additional presence of coumarin in the medium. The pellet is non-fibrous, but contains glucose as the only detectable sugar following hydrolysis and thin layer chromatography. The results are discussed in terms of general ideas concerning the polymerization and crystallization of structural polysaccharides.