THE INVOLVEMENT OF OXYGEN-DERIVED FREE-RADICALS IN THE RESISTANT RESPONSE OF POTATO-TUBERS TO ERWINIA-CAROTOVORA

The absolute requirement of oxygen for a potato tuber (cv. Pentland Crown) to display a resistant response to Erwinia carotovora has been demonstrated in EPR measurements. These show that a relatively stable free radical is formed in inoculated hosts only after exposure to air. In an attempt to isolate and identify unstable free radical precursors, experiments have been conducted in which the chemical spin trap (alpha-(4-pyridyl 1-oxide)-N-tert-butyl-nitrone (POBN) was incorporated into the tissue either at the time of inoculation or upon exposure to air. A single radical adduct was observed with spectral parameters that resemble those of a lipid-derived radical.