INFOCHEMICALS - THE SEED-FUNGUS-ROOT CONTINUUM - A REVIEW

Chemical signals in the environment may operate at levels of increasin g complexity, corresponding to cells, organs, organisms, groups and co mmunities. The micro-environment of the soil is reviewed with respect to volatiles such as O2, CO2, C2H2 and HCN and the possible role these might have on seeds. Evidence is presented that the infochemicals in fire-derived volatiles are a significant cue in seed germination in ma ny ecosystems, world wide. Some geophytes may also show dormancy-break ing by fire-derived cues. Examples are described of volatile infochemi cals derived from lipid peroxidation during seed ageing, serving as ge rmination cues for pathogenic fungi. Finally, examples of the obligate root parasites Striga and Orobanche are discussed in response to host signalling substances produced by the roots. It is concluded that pra ctical usage of such substances may provide safer agricultural and env ironmental practises.