Cell-Wall Changes in Potato Tuber Tissue 4Phytophthora infestans (Mont.) De Bary

Examination of the carbohydrates of cell walls prepared fromtuber discs of a susceptible variety of potato showed an increase,with time, in all the polysaccharide fractions in control discs,but a slower increase in the pectic fraction and a more rapidincrease in the extraction residue to discs infected with Phytophthorainfestans. These differences were related to the monosaccharidecomposition of hydrolysates; there was no increase in galactose,found predominantly in the pectic fraction, but a rapid increasein glucose which is confined almost exclusively to the extractionresidue. Part of the increased glucose was due to an accumulationof hyphal wall of P. infestans which contains mainly an alkali-insolubleglucan. Galactanase activity, which was demonstrated in infecteddiscs, could account for the divergence of galactose contentfrom that of the controls. There was an enhanced accumulationof a lignin-like polymer associated with the cell-wall fractionof infected discs.