Quantitative differences between polysaccharide compositions in normal differentiated Ulva mutabilis and the undifferentiated mutant lumpy

The chemical composition of the polysaccharides from two normal differentiated strains of the multicellular green alga Ulva mutabilis, was compared with the polysaccharides from a morphological mutant lumpy which grows like an aggregate of undifferentiated cells. The walls of the lumpy cells differ in ultrastructure from the wild type as well as other mutants with organized thalli. Qualitative chemical differences between the strains were not found.The molar ratio between the different sugars, degree of sulphation and content of glucuronic acid in the water soluble polyanion fraction corresponds with that reported for Ulva lactuca grown under natural conditions. The water soluble neutral fraction has surprisingly little glucose and is enriched in mannose and galactose. The ratio of the water extractable to the residual polysaccharide, however, is 1 for the normal organized strains and 4 for lumpy. It is proposed that this shift in ratio for lumpy may cause less cross linking between the cellulose fibres. This in turn may result in increased plasticity of the walls whereby local differences in wall expansion for normal morphogenesis are no longer possible.