Document: STE-3-43-11

Effects of soil nutrient and water interactions on the growth and chemistry of the silky willow (Salix sericea), and performance of a leaf beetle herbivore (Plagiodera versicolora).

LOWER, S.S.* and C.M.ORIANS

Tufts University, Medford, MA 02155 ¹

Abstract:
Soil nutrient and water availability can both affect the expression of plant traits that, in turn, may determine the growth and survival of the insects that feed on them, but there are few studies addressing how these two abiotic factors interact (N*W interaction). Our objective was to investigate how a combination of nutrients and water availability affects silky willow (Salix sericea) growth and chemical traits, and the growth of the imported leaf beetle (Plagiodera versicolora). We planted 20 cm cuttings derived from the same genotype in pots and applied 3 levels of water availability (dry, intermediate, flooded) and 2 nutrient treatments (high, low) in a complete factorial design. We measured plant growth and chemical traits (including leaf expansion rate, shoot mass, foliar water content and foliar phenolic glycosides), and larval development time and pupal weight. The addition of nutrients increased shoot mass, leaf expansion rate and leaf water content. There was an N*W interaction on plant growth; growth was dramatically increased at high nutrients and intermediate water. There was also a significant N*W interaction for the phenolic glycoside 2'-cinnamoylsalicortin. In general, nutrient addition decreased the concentration of 2'-cinnamoylsalicortin, but the effect was particularly pronounced under dry conditions. Both nutrients and water had a marginally significant effect on the pupal weight of female beetles. Nutrient addition resulted in increased pupal weight of females, and pupae in the dry treatment weighed more than pupae in the intermediate treatment. There was a significant N*W interaction for male development time. The development time of male larvae was short in the high-N treatment under dry and intermediate water conditions, but it was longer under flooded conditions. Our results suggest that N*W interactions affect plant growth, chemical traits and insect performance.

Keywords: Nutrient-water interaction, plant-herbivore interaction, plant resource availability

This abstract is being presented at: 3:30 PM in session:
PLANT-ANIMAL INTERACTIONS