Which of the following is a characteristic of contact herbicides?

Contact herbicides are characterized by their mode of action, primarily affecting only the plant parts that come into direct contact with them. This means that when a contact herbicide is applied, it will only damage or kill the specific leaves, stems, or other plant tissues that are sprayed. This limited effect can be beneficial in situations where selective targeting of weeds is necessary, especially for crops that need to be protected from herbicidal damage.

The other options highlight different types of herbicide action. For example, the absorption through roots pertains more to systemic herbicides, which can be transported throughout the plant to affect tissues not directly touched by the herbicide. Similarly, systemic herbicides are designed to translocate within the plant, providing a more comprehensive control of the entire plant. Additionally, many systemic herbicides do not require soil application, focusing instead on being applied directly to the plant.

In summary, the defining characteristic of contact herbicides is that they impact only the surfaces they contact, rather than spreading through the plant or requiring specific application methods such as soil incorporation. Understanding this distinction is essential for effective weed management in agriculture.