Assessing the Benefits and Costs of the Hydrogen Cyanide Antiherbivore Defense in Trifolium repens

Hind Emad Fadoul; Lucas J Albano; Matthew E Bergman; Michael A Phillips; Marc T J Johnson

doi:10.3390/plants12061213

Assessing the Benefits and Costs of the Hydrogen Cyanide Antiherbivore Defense in Trifolium repens

Plants (Basel). 2023 Mar 7;12(6):1213. doi: 10.3390/plants12061213.

Authors

Hind Emad Fadoul¹, Lucas J Albano^{1

2}, Matthew E Bergman^{1

3}, Michael A Phillips^{1

3}, Marc T J Johnson^{1

2}

Affiliations

¹ Department of Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada.
² Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada.
³ Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada.

Abstract

Understanding the evolution of plant defenses against herbivores requires identifying the benefits and costs of defense. Here, we tested the hypothesis that the benefits and costs of hydrogen cyanide (HCN) defense against herbivory on white clover (Trifolium repens) are temperature dependent. We first tested how temperature affected HCN production in vitro, and then examined how temperature influenced the efficacy of HCN defense of T. repens against a generalist slug (Deroceras reticulatum) herbivore using no-choice and choice feeding trial assays. To understand how temperature affected the costs of defense, plants were exposed to freezing, and HCN production, photosynthetic activity, and ATP concentration were quantified. HCN production increased linearly from 5 °C to 50 °C, and cyanogenic plants experienced reduced herbivory compared to acyanogenic plants only at warmer temperatures when fed upon by young slugs. Freezing temperatures induced cyanogenesis in T. repens and decreased chlorophyll fluorescence. Cyanogenic plants experienced lower ATP levels than acyanogenic plants due to freezing. Our study provides evidence that the benefits of HCN defense against herbivores are temperature dependent, and freezing may inhibit ATP production in cyanogenic plants, but the physiological performance of all plants recovered quickly following short-term freezing. These results contribute to understanding how varying environments alter the benefits and costs of defense in a model system for the study of plant chemical defenses against herbivores.

Keywords: autotoxicity; cyanogenesis; freezing tolerance; plant defense; plant-herbivore; trade-off.

Grants and funding

M.E.B. and L.J.A. were supported by NSERC CGS-D awards. M.A.P. was funded by an NSERC Discovery Grant and a CFI John Evans Leaders Fund. M.J. was funded by a Canada Research Chair, NSERC Steacie Fellowship, and NSERC Discovery Grant.