Defence and Regrowth, Alternative Plant Strategies in the Struggle against Herbivores

Differences in intensity or frequency of defoliation between species do not necessarily imply differences in ultimate effect: survival or growth. Several species appear to be very successful to overcome a high defoliation pressure because of their regrowth capacity. The hypothesis is formulated that defence mechanisms and regrowth capacity are alternatives. Given a limited amount of energy and nutrients available in the struggle against herbivores, there should be a trade off between these two mechanisms. Observations on the intensity of herbivory, experiments on regrowth capacity and on storage of reserves in roots agree with the predictions based on this hypothesis. Herbivory theory is discussed and it is concluded that a short population longevity and/or a short life cycle may be one of the ways to reduce the effect of herbivory. Differences in shoot/root ratio are discussed in this context.