Remarkably, neither did the treatment with foliar herbivory
affect the food consumption and relative growth rate of S. exigua in the bioassay.
However, this treatment did result in a significant change in the distribution of S.
exigua feeding. Plants that had been pre-exposed to foliar herbivory suffered significantly
less damage on their young terminal leaves. While plant growth and foliar
nitrogen levels were not affected by any of the treatments, we did find significant
differences between treatments with respect to the level and distribution of plant
defensive chemicals (terpenoids). Exposure to root herbivores resulted in an increase
in terpenoid levels in both roots as well as in mature and immature foliage. Foliar
damage, on the other hand, resulted in high terpenoid levels in young, terminal leaves
only. Our results show that root-feeding herbivores may change the level and
distribution of plant defenses aboveground. Our data suggest that the reported
interactions between below- and aboveground insect herbivores are mediated by
induced changes in plant secondary chemistry.
only. Our results show that root-feeding herbivores may change the level and
distribution of plant defenses aboveground. Our data suggest that the reported
interactions between below- and aboveground insect herbivores are mediated by
induced changes in plant secondary chemistry.