Comparison of Phytotoxicities between 4-fluorinated and non-fluorinated 2-chloro-5-(3,4,5,6-tetrahydrophthalimido)benzoates

Protoporphyrinogen-IX oxidase inhibition and peroxidizing phytotoxicity wer e determined using a series of fluorinated and non-fluorinated alkyl 2-chlo ro-5-(3,4,5,6-tetrahydrophthalimido)benzoates and their parent benzoic acid derivatives. Protoporphyrinogen-IX oxidase from corn etioplasts was extrac ted, and ethane formation by intact cells of the green algae Scenedesmus ac utus was measured. The benzoates with a fluorine atom exhibited stronger pe roxidizing phytotoxicity (higher ethane formation) than the benzoates havin g no fluorine atom although protoporphyrinogen-IX oxidase inhibition by the fluorinated analogues was found to be weaker or almost equal to the non-fl uorinated analogues. These data strengthen and generalize our previous find ings with cyclic imides having an N-(4-chloro-2-fluoro-5-carboxyphenyl) gro up. The fluorinated analogues, which are not necessarily stronger protoporp hyrinogen-IX oxidase inhibitors, exhibit stronger peroxidizing phytotoxicit y with intact plant cells than those without a fluorine atom.