Arsenic Uptake By Sweet Alyssum (Lobularia Maritima): Effects On Plant Metabolism And Larvae Of The Small White Butterfly (Pieris Rapae)

Abstract

Arsenic, once commonly used as a pesticide, is highly toxic to consumers but also can influence plant metabolism and growth. Therefore, soil arsenic can affect plant interactions with antagonist (e.g., herbivores) and mutualists (e.g., pollinators) directly through arsenic toxicity as well as indirectly through induced changes in plant secondary metabolism. To address how arsenic in soil may affect the leaf consumption of sweet alyssum (Lobularia maritima) by larvae of the small white butterfly (Pieris rapae, Lepidoptera: Pieridae), we analyzed plant arsenic uptake and the composition of leaf glucosinolates produced by plants grown under a gradient of realistic arsenic concentrations (0, 10, 25, 50, 100 mg As /kg soil DW). Plant growth rates and biomass were quantified as a function of soil and plant arsenic concentrations to assess plant physiological stress. Pieris performance assays were used to evaluate plant resistance to herbivory. Arsenic exposure reduced plant growth rates (at 100 mg As/kg soil DW) and total aboveground biomass (across all concentrations), with arsenic uptake into aboveground plant tissue closely mirroring the soil arsenic concentration. Arsenic exposure changed glucosinolate composition by increasing the production of one unidentified glucosinolate (at 50 and 100 mg/kg DW), but did not affect total glucosinolates. Glucosinolate production and arsenic tissue concentrations interacted to affect larval performance in a non-linear way. Our findings suggest that soil contamination with arsenic can impact plant fitness and metabolism in multiple ways with potentially significant downstream effects on biotic interactions and community composition.