How do systemic herbicides generally function?

Systemic herbicides function primarily by disrupting internal plant processes. These herbicides are absorbed by the plant and are translocated throughout its tissues, affecting vital functions such as photosynthesis, nutrient uptake, and cell division. By interfering with these internal processes, systemic herbicides can effectively control a wide range of weeds, often leading to the death of the entire plant.

The other options describe different mechanisms that do not accurately represent the mode of action of systemic herbicides. For example, causing physical damage to the plant or forming a protective layer on leaves pertains more to contact herbicides, which work by damaging the plant tissue they come into contact with, rather than being absorbed and affecting internal processes. Additionally, repelling herbivores is not a function of herbicides; rather, it relates more to plant defense mechanisms against grazing animals.

Understanding how systemic herbicides work is important for their effective application and for managing vegetation in various settings such as agricultural fields and rights-of-way.