The role in ozone phytotoxicity of the evolution of ethylene upon induction of 1-Aminocyclopropane-1-carboxylic acid synthase by ozone fumigation in tomato plants

Abstract

The rate of evolution of ethylene by tomato plants was rapidly increased by O3 fumigation. The time course of the increase in 1-aminocyclopropane-1-carboxylic acid (ACC) synthase activity was the same as that in the rate of evolution of ethylene, suggesting that ACC synthase activity might be a rate-limiting step in the evolution of ethylene that is caused by O3 fumigation. The rate of the O3-induced evolution of ethylene was increased by the application of ACC to tomato plants, suggesting the involvement of ACC oxidase in the O3-induced evolution of ethylene. Treatment of plants with tiron inhibited the evolution of ethane, but not of ethylene, These results indicated that evolution of ethylene in O3-trated tomato plants might result from enzymatic reactions catalyzed by both ACC Synthase and ACC oxidase, but not from stimulation by O3 of the peroxidation of lipids mediated by free radicals. Pretreatment of leaves with aminoethoxyvinylglycine (AVG), an inhibitor of ACC synthase, significantly inhibited the evolution of ethylene that induced by O3 and concomitantly reduced the extent of O3-induced visible damage to leaves. Treatment with 2,5-norbonadiene, an inhibitor of the action of ethylene, strongly reduced the extent of visible damage caused by O3, even though it did not suppress the evloution of ethylene. These results indicate that ethylene acts on certain metabolic processes to cause visible damage.