Allelopathic effects of caffeic acid and seven of its derivatives, isolated from leaves of Bellis
perennis L., have been evaluated on seed germination and seedling growth of two coexisting
Mediterranean species (Dactylis hispanica and Aegilops geniculata). The structures of
the metabolites have been elucidated on the basis of their spectroscopic features. Cluster
analysis of biological data pointed out interesting relationships between the chemical
structures of the compounds and their biological effects. The distribution of caffeic acid
derivatives in plant organs, as well as their presence in soil community, has been investigated.
The leaf decomposition seems to justify the presence of caffeic acid derivatives in
the soil.