Natural Products from Trifolium repens

Freeze-induced cyanide toxicity does not maintain the cyanogenesis polymorphism in white clover (Trifolium repens).[Pubmed: 30080261]

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.

A neglected alliance in battles against parasitic plants: arbuscular mycorrhizal and rhizobial symbioses alleviate damage to a legume host by root hemiparasitic Pedicularis species.[Pubmed: 30078224]

Despite their ubiquitous distribution and significant ecological roles, soil microorganisms have long been neglected in investigations addressing parasitic plant-host interactions. Because nutrient deprivation is a primary cause of host damage by parasitic plants, we hypothesized that beneficial soil microorganisms conferring nutrient benefits to parasitized hosts may play important roles in alleviating damage. We conducted a pot cultivation experiment to test the inoculation effect of an arbuscular mycorrhizal fungus (Glomus mosseae), a rhizobium (Rhizobium leguminosarum) and their interactive effects, on alleviation of damage to a legume host (Trifolium repens) by two root hemiparasitic plants with different nutrient requirements (N-demanding Pedicularis rex and P-demanding P. tricolor). Strong interactive effects between inoculation regimes and hemiparasite identity were observed. The relative benefits of microbial inoculation were related to hemiparasite nutrient requirements. Dual inoculation with the rhizobium strongly enhanced promotional arbuscular mycorrhizal effects on hosts parasitized by P. rex, but reduced the arbuscular mycorrhizal promotion on hosts parasitized by P. tricolor. Our results demonstrate substantial contribution of arbuscular mycorrhizal and rhizobial symbioses to alleviating damage to the legume host by root hemiparasites, and suggest that soil microorganisms are critical factors regulating host-parasite interactions and should be taken into account in future studies.