Regulation of Russet Spotting, Phenolic Metabolism, and IAA Oxidase by Low Oxygen in Iceberg Lettuce

A 1.5% O 2 atmosphere, relative to normal air, dramatically inhibited ethylene-induced russet spot development, PAL, and ionically bound POD, and ionicaliy bound IAA oxidase activities and reduced soluble phenolic content in stored iceberg lettuce ( Lactuca sativa L.). Low O 2 also inhibited eythylene production and respiration. Polyphenol oxidase activity was slightly inhibited by low O 2 . The results suggest that low O 2 inhibition of ethylene action and attendant effects on phenolic metabolism and IAA oxidase activity may be responsible for inhibition of russet spotting by 1.5% O 2 . Chemical names used: indole-3-acetic acid (IAA); phenylalanine ammonia-lyase (PAL); peroxidase (POD); polyphenol oxidase (PPO).