What must a herbicide do to kill a plant?

• A. Covering the vegetation.
• B. Causing biotic symptoms.
• C. Getting absorbed into the plant.
• D. Staying on the leaf surface.

Answer: (C)

Getting absorbed into the plant is essential because herbicides must reach internal targets to stop growth or disrupt cellular processes. The active ingredient has to cross the leaf cuticle or root cells and move through the plant via the vascular system to reach enzymes, photosystems, or growth-regulating sites. If the chemical stays on the leaf surface or merely covers vegetation, it cannot access those internal sites and the plant is not killed. Some herbicides act systemically and rely on movement to meristems, while others are contact types that still require entry to cause damage—either way, absorption is the key step that enables the herbicide to do its job.