American Journal of Botany 92(1): 2126. 2005.
PHENOTYPIC PLASTICITY TO LIGHT COMPETITION AND
HERBIVORY IN CHENOPODIUM ALBUM
NILE S. KURASHIGE AND ANURAG A. AGRAWAL2,3
Department of Botany, University of Toronto, 25 Willcocks St., Toronto, Ontario, M5S 3B2, Canada
Competition and herbivory are ubiquitous environmental challenges that affect most plants. We examined the influence of phenotypic
responses to either competition or herbivory on the subsequent response of the plants to the other factor. The stem-elongation response
of Chenopodium album to light competition attenuated its resistance to caterpillar herbivory in terms of herbivore mortality, but not
in terms of growth of the survivors. Plant responses to herbivory did not affect subsequent responses to light competition. Thus, plants
were largely able to express phenotypic plasticity (a proportional increase in the phenotype) following previous exposure to a different
environmental factor. Although plants were able to express sequential plasticity, the final phenotype expressed was limited by exposure
to previous environmental factors: induced resistance reduced plant height and stem elongation made plants more palatable to herbi-
vores. Phenotypic plasticity in response to competition and herbivory may thus limit the subsequent expression of adaptive phenotypes.
Key words: Chenopodiaceae; Chenopodium album; herbivory, induced plant resistance; phenotypic plasticity; plantinsect inter-
actions; R : FR; shade avoidance; Spodoptera exigua.
Phenotypic plasticity is any change in an organism's phe-
notype induced by the environment (Bradshaw, 1965;
Schlichting and Smith, 2002). A considerable literature has