The impact of plant genetic variation and water stress on plant–herbivore interactions.

Plant genotype, water stress and their interaction are among the factors contributing to the susceptibility of plants to herbivory. The plant's nitrogen concentration, a critical and often limiting nutrient, differs with plant genotype and water stress. Still, few studies have investigated the impact of the interaction between genotype and water stress on herbivory and plant nitrogen.We established a common garden in Duluth, MN, of tall goldenrod, Solidago altissima, collected from a local Minnesota site to analyse the effects of goldenrod genotype and water stress on leaf nitrogen and the preference and performance of the chrysanthemum lace bug, Corythucha marmorata.Lace bugs had oviposition, nymph and adult preferences among host plant genotypes, water treatments and among genotype and water treatment combinations. Nymph and adult survival and adult mass varied significantly due to plant genotype, water treatment, the interaction between plant and water treatment and the interaction of treatment with lace bug density. Oviposition preference and offspring performance were significantly positively related.Leaf nitrogen increased with the increasing severity of the water limitation in the absence of lace bugs. However, in the presence of lace bugs, there was no difference in nitrogen among water treatments.We hypothesize that lace bugs reduce leaf nitrogen concentration to a lower threshold and then move between plants until nitrogen concentration equalises among all plants. [ABSTRACT FROM AUTHOR]