Nutrient availability is predicted to affect primary and secondary metabolic processes in plants. Increases in soil nutrients are predicted to be associated with changes in biomass and chemical defense in many plants, with the direction of the changes determined by plant life history characteristics and the structure of defensive chemicals. Using the neotropical shrub Piper imperiale in a controlled experiment, we examined the effects of 10 levels of fertilizer addition on photosynthetic capacity, plant growth, and plant defense.
Results/Conclusions We found that fertilizer was associated with increased photosynthetic capacity but had no affect on the concentration of three imide secondary metabolites in the leaves of this neotropical shrub. Although variation in secondary metabolite production is substantial in natural populations and in the greenhouse, these results and the results of a series of field experiments that showed no effect of soil moisture, soil fertility, soil type, herbivory, and light availability on imide content lead to the conclusion that variation in secondary metabolite concentration is predominantly affected by plant genotype
