Which compound is an example of an inhibitor of protoporphyrinogen oxidase?

Glufosinate is recognized as an inhibitor of protoporphyrinogen oxidase, an important enzyme in the biosynthesis of heme. Inhibiting this enzyme disrupts the production of chlorophyll and can lead to the accumulation of protoporphyrinogen, which subsequently causes cell death in plants.

Glufosinate functions by interfering with the metabolic pathways that utilize protoporphyrinogen, which is crucial for producing vital compounds within the plant. This action is particularly effective against a wide range of weed species, making glufosinate a valuable herbicide in agricultural practices.

The other compounds listed do not serve this specific role. For instance, Harness is primarily a corn herbicide that works differently, while cyclohexamide is known for its effects as a protein synthesis inhibitor in fungi and not as a herbicide. Copper sulfate is often used for its algicidal and fungicidal properties but does not inhibit protoporphyrinogen oxidase specifically. Therefore, glufosinate stands out as the correct answer for this question.