What describes a foliar active herbicide?

A foliar active herbicide is specifically designed to be absorbed through the leaves of plants. This mode of action allows the herbicide to effectively target the plant's foliage, leading to control of the unwanted vegetation. When applied, the active ingredients penetrate the leaf tissue and move throughout the plant, interfering with vital physiological processes, which can ultimately lead to the plant's death.

In contrast, the other options do not accurately describe the characteristics of a foliar active herbicide. For instance, a herbicide that attributes its action solely through the roots would be classified differently, focusing on soil uptake rather than foliar absorption. Additionally, the description of a solid herbicide mixed with water refers more to a formulation type rather than the action mechanism, which is not relevant to the concept of foliar activity. Finally, a herbicide that works primarily in the soil describes a different category of herbicides that target root systems and rely on soil absorption rather than leaf uptake. Therefore, the definition of a foliar active herbicide emphasizes its targeted mode of application through plant leaves.