Applying the limiting resource model to plant tolerance of apical meristem damage.

Apical meristem damage (AMD) is a common result of herbivory. AMD can have dramatically variable effects on plant architecture and fitness, ranging from a total loss of reproductive capacity to overcompensation. We explored the influence of environmental stresses and meristem limitation on tolerance of AMD by applying the limiting resource model (LRM) of plant tolerance to 17 previously published studies and a new empirical study on Solidago altissima. In the S. altissima experiment, AMD released axillary meristems from apical dominance, and fertilizer addition enabled plants to take full advantage of the lateral branches. AMD caused a 58% reduction in seed production in nutrient-stressed plants but only a 6% reduction in seed production in fertilized plants. In 12 of the 18 studies reviewed, tolerance was greater in the high-resource (or low-competition) treatment; in two, tolerance was greater in the low-resource treatment; and in four, resource level did not affect tolerance of AMD. The results of 15 studies (83%) were consistent with LRM predictions. Overcompensation was observed in six studies, and it occurred only in the high-resource treatments in five of these studies, as would be expected from applying the LRM.