Exogenous application of plant hormones in the field alters aboveground plant–insect responses and belowground nutrient availability, but does not lead to differences in plant–soil feedbacks

Robin Heinen*, Katja Steinauer, Jonathan R. De Long, Renske Jongen, Arjen Biere, Jeffrey A. Harvey, T. Martijn Bezemer

*Corresponding author for this work

    Research output: Contribution to JournalArticleAcademicpeer-review

    Abstract

    Plant–soil feedbacks of plants that are exposed to herbivory have been shown to differ from those of plants that are not exposed to herbivores. Likely, this process is mediated by jasmonic acid (JA) and salicylic acid (SA) defense pathways, which are induced by aboveground herbivory. Furthermore, exogenous application of these phytohormones to plants alters belowground communities, but whether this changes plant–soil feedbacks in natural systems is unknown. We applied exogenous sprays of JA and SA individually and in combination to field plots in a restored grassland. Control plots were sprayed with demineralized water. After three repeated application rounds, we transplanted seedlings of the plant–soil feedback model plant Jacobaea vulgaris as phytometer plants to test the effects of potential phytohormone-mediated changes in the soil, on plant performance during the response phase. We further measured how exogenous application of phytohormones altered plant-related ecosystem characteristics (plot-level); soil chemistry, plot productivity, insect communities and predation. Biomass of the phytometer plants only co-varied with plot productivity, but was not influenced by phytohormone applications. However, we did observe compound-specific effects of SA application on insect communities, most notably on parasitoid attraction, and of JA application on soil nitrogen levels. Although we did not find effects on plant–soil feedbacks, the effects of exogenous application of phytohormones did alter other ecosystem-level processes related to soil nutrient cycling, which may lead to legacy effects in the longer term. Furthermore, exogenous application of phytohormones led to altered attraction of specific insect groups.

    Original languageEnglish
    Pages (from-to)559-570
    Number of pages12
    JournalArthropod-Plant Interactions
    Volume14
    Issue number5
    Early online date17 Aug 2020
    DOIs
    Publication statusPublished - Oct 2020

    Funding

    We thank Roel Wagenaar and Ciska Raaijmakers for valuable discussions on phytohormone preparation and Simon Vandenbrande for help during the initial setup of field plots. This work was funded by the Netherlands Organization for Scientific Research (NWO VICI Grant 865.14.006). This is publication number 7018 of the Netherlands Institute of Ecology (NIOO-KNAW).

    FundersFunder number
    NIOO-KNAW
    Netherlands Institute of Ecology
    Netherlands Organization for Scientific Research
    Nederlandse Organisatie voor Wetenschappelijk Onderzoek865.14.006

      Keywords

      • Field experiment
      • Herbivory
      • Insect communities
      • Jasmonic acid
      • Plant–soil feedback
      • Salicylic acid

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