What is the impact of systemic herbicides on plants?

Systemic herbicides are designed to be absorbed by the plant and then translocated throughout its system, which is why they require the plant to remain alive for effective circulation. Once absorbed, these herbicides move through the plant’s vascular system to reach all parts, including leaves, stems, and roots. This allows them to target the entire plant more effectively, ultimately disrupting vital processes such as growth and nutrient uptake.

In contrast to contact herbicides that act quickly upon contact with the plant's tissues, systemic herbicides depend on the plant's health and physiological processes to facilitate their movement and action. This characteristic makes them particularly effective against a wide range of weeds, including perennial types, as they can kill both above and below-ground parts over time.

The other choices do not accurately describe the full nature of systemic herbicides. For example, they can be effective on both mature and immature weeds, depending on the type of systemic herbicide used and the specific plant being treated. Additionally, perennial weeds can indeed be affected by systemic herbicides, contrary to what one of the options states.