Climate warming and plant biomechanical defences

silicon addition contributes to herbivore suppression in a pasture grass

Scott N. Johnson*, James M.W. Ryalls, Craig V.M. Barton, Mark G. Tjoelker, Ian J. Wright, Ben D. Moore

*Corresponding author for this work

Research output: Contribution to journalArticle

10 Citations (Scopus)
2 Downloads (Pure)

Abstract

Plants, notably the Poaceae, often accumulate large amounts of silicon (Si) from the soil. Si has multiple functional roles, particularly for alleviating abiotic and biotic stresses (e.g., defence against herbivores). Recent evidence suggests that environmental change, including temperature changes, can diminish Si accumulation which could affect functions such as herbivore defence. Using a field warming experiment, we grew a pasture grass (Phalaris aquatica) that was either supplemented or untreated with Si (+Si and −Si, respectively) under ambient and elevated (+2.8°C above ambient) air temperatures. We quantified soil water, plant growth rates, Si accumulation, leaf biomechanical properties and in situ relative growth rates of a herbivorous global insect pest (Helicoverpa armigera). Si supplementation promoted shoot and root biomass by c. 48% and 61%, respectively under ambient temperatures, but these gains were not apparent under warmed conditions. Warmer temperatures reduced Si uptake by −Si plants by c. 17%, potentially due to the lower levels of soil water content in warmed plots. Si supplementation, however, increased Si accumulation in leaves by c. 24% in warmed plots restoring Si levels to those seen under ambient temperatures. Si supplementation enhanced biomechanical properties in the leaves, but this was only statistically significant under ambient temperatures; leaves of +Si plants required 42% more force to fracture and were 30% tougher at the midrib than leaves of −Si plants. The relative growth rates of H. armigera declined by 56% when feeding on +Si plants under ambient temperatures, and while Si supplementation caused a trend towards declining herbivore growth rates under warmer conditions, this was not statistically significant. We conclude that climate warming may mitigate the beneficial effects of Si on Phalaris aquatica in the short term, potentially by reducing Si uptake. While Si uptake can be restored with Si supplementation, Si-enhanced biomechanical defences against a global pest may not be fully restored under warmer temperatures. A plain language summary is available for this article.

Original languageEnglish
Pages (from-to)587-596
Number of pages10
JournalFunctional Ecology
Volume33
Issue number4
Early online date27 Jan 2019
DOIs
Publication statusPublished - Apr 2019

Keywords

  • climate change
  • global warming
  • insect herbivore
  • leaf toughness
  • silica
  • silicon

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