Plants are most susceptible to herbicides when they are mature.

• A. True
• B. False
• C. Not sure
• D. Sometimes

Answer: (B)

Susceptibility to herbicides depends strongly on the plant’s growth stage. Young, actively growing plants are generally more vulnerable because their cells are dividing rapidly and essential processes are at their peak. This makes the herbicide’s target processes easier to disrupt, and the plant hasn’t fully developed its defenses yet.

As plants mature, they often become more tolerant. Their tissues are tougher, the cuticle can be thicker, and detoxification mechanisms (enzymes that break down or compartmentalize the chemical) are more established. These factors reduce uptake, movement, and the effective concentration of the herbicide inside the plant, leading to less damage.

So the statement that plants are most susceptible when they are mature isn’t correct; the opposite is usually true: younger plants tend to be more susceptible. There can be exceptions with specific herbicides or plant species, but the general trend supports greater vulnerability in the early growth stage.