A. Are these herbivory mechanisms always effective?

1. Generally herbivory is non-lethal unless a plant is pre-stressed or just making it. Studies of oak forests indicate that no more than 8-12% of the vegetation is consumed at any one time.
However the question enters here, would these plants be only experiencing limited herbivory if the compounds we will be discussing did not exist... studies of island populations which have lost their defense arsenal are threatened when herbivores are introduced.

2. The toll we visualize depends on the response of the plant:
Compensation by the plant by: