Which factors influence herbicide selectivity?

• A. Soil texture.
• B. Enzyme systems and pH responses.
• C. Leaf size.
• D. Plant color.

Answer: (B)

Herbicide selectivity comes from how a plant processes and responds to the chemical. Different plants have different enzyme systems that detoxify or activate herbicides, and the pH inside plant tissues affects the chemical’s form, movement, and site of action. When a crop has enzymes that rapidly detoxify a herbicide or a tissue pH that reduces its activity, the crop tolerates the herbicide while susceptible weeds are harmed. That biochemical handling is what makes a herbicide selective.

Soil texture can influence how much herbicide is available to the plant in the first place and how it’s taken up, but it doesn’t determine the plant’s inherent ability to detoxify or tolerate the chemical. Leaf size and plant color don’t set the herbicide’s mode of action or the plant’s detoxification capacity, so they aren’t decisive factors in selectivity.