CHANGES IN CELL WALL-ASSOCIATED PEROXIDASES DURING THE LIGNIFICATION OF FLAX FIBERS

Cell wall-associated peroxidases were extracted selectively from fibre-bearing tissue dissected from the stem of Linum usitatissimum and their activities correlated with the extent of fibre lignification. The onset of fibre lignification was accompanied by increases in the levels of the peroxidases both ionically and covalently bound to the wall. However, the rise in the levels of covalently bound wall peroxidases was more dramatic. A portion of the covalently bound peroxidases could be isolated for study by solubilization with the glycanase mixture, driselase, whilst others remained firmly attached to the wall residue. The ability of driselase-solubilized wall peroxidases to oxidize NADH to form hydrogen peroxide rose sharply as the fibre cells became progressively lignified. This suggests that this process is accompanied by an increase in peroxidases covalently bound to the wall that have an affinity for the generation of hydrogen peroxide. A survey of the peroxidase isozymes present in both fractions using non-denaturing polyacrylamide gel electrophoresis identified a number of cationic and anionic isozymes that may have specific roles in the lignification of flax fibres.