What are systemic herbicides?

Systemic herbicides are specifically designed to be absorbed by plants and then translocated throughout their internal systems. This characteristic allows them to target various parts of the plant, including leaves, stems, and roots. Once absorbed, these herbicides can move within the plant, disrupting physiological processes that are essential for growth and survival.

This systemic action makes such herbicides effective against a wide range of plant species, particularly perennial weeds, as they can affect even those parts of the plant that are not immediately exposed to the herbicide. In contrast, herbicides that remain on the surface typically only impact the outer layers of the plant, limiting their effectiveness against certain types of weeds that might have deep root systems or protective structures.

The other choices address various aspects of herbicide behavior but do not define systemic herbicides correctly. For instance, those that affect only the roots would not account for the herbicide's movement through the entire plant system, which is crucial for achieving effective control. Similarly, requiring multiple applications may not be necessary for systemic herbicides, as a single application can often lead to complete plant control if used correctly.