Variation within flax (Linum usitatissimum) and barley (Hordeum vulgare) in response to allelopathic chemicals Abstract A possible method of manipulating allelopathy would be to develop crop varieties showing an increased tolerance to allelopathic chemicals. We therefore examined four flax (Linum usitatissimum) varieties and two wild Linum species in the presence of p-coumaric acid and four