Oxygen Activation and Oxygen Toxicity

Abstract

INTRODtTCTION ... .. .... . . ........ . . . . ....... . . . ... .. .. . .. . . .... . . . .. ... ....... .. . .. .. . . .... .. . .. .. . . ... . . . . 74 OXYGEN ACTIVATION AND REACTIVE OXYGEN SPECIES ... ..... . . . . . ..... . .. ... 75 Reductive Activation ........ . . ......... ... . . . ..... . ..... .. ....... . . . . .. ....... . . . . 75 Oxygen Addition to Organic Radicals or Reduced Metal Complexes 75 Photodynamic Reactions ,.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...... . . . . . . . 76 REACTIVITY AND DETECTION OF ACTIVE OXYGEN SPECIES 77 Superoxide . . . . . ... . . . . ....... . . . . . . . . ....... . . . . . . . . ..... ......... ..... 77 Hydrogen Peroxide (H20JJ 77 The OR Radical ....... . . 78 Singlet Oxygen 78 Organic Peroxides and Peroxy Radicals ......... . . . . . 79 OXYGEN ACTIVATION IN DIFFERENT COMPARTMENTS AND ORGANELLES OF PLANT CELLS 79 Peroxides in Cell Walls . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Microsomal Oxygen Activation .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Peroxisomes ........ . . . . . . . . . . . . . . . . . . . . . . ....... . . . . . . . . . . . . . ..... ...... 80 Oxygen Activation and Detoxification in Mitochondria . ...... 80 Chloroplasts ....... .... ...... ..... .. . . . ..... . . . ...... . . . . . . . . ..... . . . . . ......... . ... 81 Physiological observations and the biological significance of oxygen reduction 8 1 Mechanisms o f oxygen activation in the chloroplast .... ..... 82 Functions of activated oxygen species in chloroplasts . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 84 ENDOGENOUS MECHANISMS OF PROTECTION AGAINST DELETERIOUS OXYGEN SPECIES ...... 84 PATHOLOGICAL, ENVIRONMENTAL, AND COMMERCIAL ASPECTS OF OXYGEN TOXICITy 86 CONCLUDING REMARKS AND FUTURE TRENDS 88