Slices of tissue from Jerusalem artichoke tubers were maintained under different growth conditions for periods of between 40 and 60 hours, when they were harvested and the walls isolated. The wall preparations were fractionated into the main polysaccharide components and the contents of uronic acid and sugar residues estimated in these components and in the whole wall preparations. Concentrations of plant hormones, optimal for cell enlargement, caused an increase in the water solubility of the pectic fractions of the walls compared to the situation in the water controls where enlargement was negligible. No differences could be detected in wall composition between ray, pith, and cortex tissue in the tuber. In the presence of plant hormones, tissue enlargement was inhibited by calcium ions for about 30 hours, after which it proceeded at a reduced rate. Such calcium treatment appeared to cause no change in wall deposition or composition. The results are discussed in relation to current ideas concerning the plasticity of primary cell walls.
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