How do plants defend themselves against herbivores?

Plants have evolved various defences to protect themselves from herbivores. Physical defences include thorns, spines, and tough leaves, which deter animals from feeding. Chemical defences, such as toxins or bitter-tasting compounds, make the plant less palatable or even harmful to consume. Some plants, like acacias, form mutualistic relationships with ants, which defend the plant in exchange for shelter or food. Others release volatile chemicals to attract predators of the herbivores. These strategies help plants survive in environments with grazing pressure.