EFFECTS OF LIGHT AND NUTRIENTS ON TOMATO PLANT COMPENSATION FOR HERBIVORY BY MANDUCA-SEXTA (LEPIDOPTERA, SPHINGIDAE)

This preliminary study examined how two resources (light and nutrients ) influence the ability of tomato plants to show growth compensation f or defoliation by the tobacco hornworm (Manduca sexta). Growth rate an d biomass of plants grown under high and low levels of light and nutri ents, and exposed to 4 levels of defoliation by Manduca sexta were mea sured. Nutrients affected plant growth rate much more strongly than di d light. Light and nutrients, however, each influenced how herbivory a ffected plant growth. Defoliation significantly decreased growth rate only under conditions of low light and high nutrients. Biomass, on the other hand, was low under all resource treatments except high levels of both light and nutrients, and defoliation significantly decreased b iomass only under high levels of both resources. Thus, plants appeared to compensate for damage, in terms of biomass, only under conditions of either low light and/or low nutrients.