Intact plant with ethylene

The final step in the biosynthesis of ethylene is catalyzed by ACC oxidase. Application of ACC to most plant tissues results in a marked increase in ethylene production, indicating that ACC oxidase in these tissues is constitutive and not rate-limiting. Although ACC-dependent ethylene production is readily demonstrated in intact tissues, in vitro ACC oxidase activity has not been demonstrated independent of intact cellular material. Although intact protoplasts and vacuoles retained the characteristics of tissue ACC oxidase activity [9], Porter and John [24] reported that their preparations retained less than 5% of the activity associated with the parent tissue. They proposed that full ACC oxidase activity requires tissue integrity in addition to the previously noted cell membrane integrity. 

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