Do grasses fight back? The case for antiherbivore defences.

In the past, discussion about grass-grazer interactions has tended to centre on whether they represent some sort of mutualism. However, intense grazing pressure is more likely to have selected for the presence of various antiherbivore defences in grasses. Many grasses contain silica, which functions in some cases as a physical defence. Others contain various secondary compounds which have negative effects on both invertebrate and vertebrate herbivores. Much recent evidence suggests that plants with higher levels of these defences deter herbivores more effectively than plants without them.