Department of Entomology, University of California, Riverside Riverside, CA-92521, USA.
The effects of pollution on plant defensive chemistry can profoundly impact not only plant suitability for insects, but also suitability for human consumption. Even plants genetically engineered for insect control will be deleteriously affected by increasing pollution. Two examples will be presented. Acidic fogs of the type found near urban centers have been found to increase the levels of the carcinogenic and mutagenic linear furanocoumarins by 540% in leaves and 440% in petioles of commercial celery. Concentrations of these compounds in test plants were 7.5 times higher than the amount known to produce contact dermatitis. In the second example, we measured the effect of elevated CO2 on the expression of bacterial toxins in genetically engineered cotton. At 900 µl/l, the level of CO2 expected within the next few decades, plants grew rapidly and became stressed for nitrogen. Such plants expressed significantly less toxin. This deficit could be nearly overcome by over-fertilization. The potential effects of these results for insect population dynamics, overuse of nitrogen fertilizer, and gene transfer to wild plant genotypes will be discussed.