Abstract
PREMISE OF THE STUDY: The maintenance of adaptive polymorphisms within species requires fitness trade-offs reflecting selection for each morph. Cyanogenesis, the ability to produce hydrogen cyanide (HCN) after tissue damage, occurs in >3000 plant species and exists as a discrete polymorphism in white clover. This polymorphism is spatially distributed in recurrent clines, with higher frequencies of cyanogenic plants in warmer climates. The HCN autotoxicity hypothesis proposes that cyanogenic plants are selected against where frosts are common, as freezing liberates HCN and could impair cellular respiration. METHODS: We tested the HCN autotoxicity hypothesis using a freezing chamber to examine survival, tissue damage, and physiological recovery as assessed via chlorophyll fluorescence following mild and severe freezing treatments. We utilized 65 genotypes from a single polymorphic population to eliminate effects of population structure. KEY RESULTS: Cyanogenic plants did not differ from acyanogenic plants in survival, tissue damage, or recovery following freezing. However, plants producing either of the two required cyanogenic precursors had lower survival and tissue damage after freezing than plants lacking both precursors. CONCLUSIONS: These results suggest that freezing-induced HCN toxicity is unlikely to be responsible for the maintenance of the cyanogenesis polymorphism in white clover. However, energetic trade-offs associated with costs of producing the cyanogenic precursors may confer a fitness benefit to acyanogenic plants under stressful climatic conditions. The lack of evidence for HCN toxicity suggests that cyanogenic clover uses physiological mechanisms mediated by β-cyanoalanine synthase and alternative oxidase to maintain cellular function in the presence of HCN.
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Claims 4
Claim · model-written summary
Cyanogenic and acyanogenic plants had similar survival, tissue damage and recovery after freezing.
Verbatim
e0“Cyanogenic plants did not differ from acyanogenic plants in survival, tissue damage, or recovery following freezing”
Claim · model-written summary
Plants producing either cyanogenic precursor had lower survival after freezing than plants lacking both.
Verbatim
e0“plants producing either of the two required cyanogenic precursors had lower survival and tissue damage after freezing than plants lacking both precursors”
Claim · model-written summary
Plants producing either cyanogenic precursor had lower tissue damage after freezing than plants lacking both.
Verbatim
e0“plants producing either of the two required cyanogenic precursors had lower survival and tissue damage after freezing than plants lacking both precursors”
Claim · model-written summary
The results suggest freezing induced hydrogen cyanide toxicity is unlikely to maintain the clover cyanogenesis polymorphism.
- Taxon
- white clover
Trifolium repense0 - Outcome
- maintenance of the cyanogenesis polymorphisme0
- Qualifier
- freezing-induced HCN toxicitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“freezing-induced HCN toxicity is unlikely to be responsible for the maintenance of the cyanogenesis polymorphism in white clover”
The same questions in other papers
cold · pest · Viridiplantae (plants)Results agree
1 paper in the same direction as this paper
- negative
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.