Respuesta :
Answer: it causes the weed to grow to fast and then the weed dies.
Explanation:
Auxins are used as weed killers because at extremely high concentrations (which is over the optimum), it has an inhabiting effect on plant growth. So if the growth of weeds’ leaves and roots are inhibited, they don’t have leaves for photosynthesis, and roots to absorb water. So weeds will die.