What distinguishes a contact herbicide from a systemic herbicide?

A contact herbicide is designed to kill only the parts of the plant it directly touches. When applied, it affects only the foliage or the green parts of the plants, leading to their destruction while leaving the root system and any other untreated portions unharmed. This means that the herbicide works on contact with the plant tissues, causing immediate damage.

In contrast, systemic herbicides are absorbed by the plant and translocated throughout its tissues, affecting not just the parts contacted but also the roots and other areas. This allows for a more thorough eradication of the plant, as the herbicide can disrupt physiological processes throughout the organism.

The other options describe various attributes that do not accurately differentiate contact herbicides from systemic ones. For example, claiming that a contact herbicide only kills through root absorption misrepresents its mode of action, as this mischaracterization overlooks the fact that root absorption pertains to systemic herbicides. Stating that systemic herbicides work only on the surface of the plants also confuses their comprehensive functionality, which includes internal effects. Finally, suggesting that contact herbicides kill specific types of weeds misrepresents their use as they can affect any plant material they contact, regardless of species.