No Evidence of Direct Superoxide Anion Effect in Hypersensitive Death of Pseudomonas syringae Van Hall in Tobacco Leaf Tissue

The hypothesis of superoxide anion generation as a direct bactericidal mechanism exercised by hypersensitive tobacco leaf tissue against an incompatible phytopathogenic pseudomonad was tested. The detection of O2− was made directly by reducing Cytochrome c and by producing nitrite from hydroxylamine chloride and indirectly by measuring the death of endophytic bacteria in the presence of superoxide dismutase. At 4 h and 6 h the low net specific reduction of Cytochrome c in the hypersensitive tissue was not confirmed by the specific production of nitrite. At the same time active superoxide dismutase did not give significant protection to the incompatible bacteria as compared to inactive superoxide dismutase. The protection provided by active superoxide dismutase as compared with the controls (bovine serum albumine treated tissue and non‐treated tissue) at 4 h and at 6 h was not correlated to its superoxide anion scavenger activity. The results indicated that the death of the incompatible pseudomonad during the hypersensitive reaction was not directly linked to O2− generation. Copyright © 1988, Wiley Blackwell. All rights reserved