Resistance induction and priming by plant volatiles
Abstract: Plants can pre-empt enemy attack by monitoring the defensive stage of theirneighbours or of other organs of the same plant. Resistance can be expressed by intact anduninfected plants when these have been exposed to volatiles that are released from infected orinfested neighbours. This phenomenon is now well known from many unrelated plant species.Recent studies demonstrated that these volatiles also play important roles in within-plantsignalling. Lima bean (Phaseolus lunatus) plants that were locally infested released volatiles,which triggered resistance responses in other, yet unaffected parts of the same plant. Differentvolatiles regulated resistance to herbivores and pathogens and volatiles at lower concentrationsprimed rather than fully induced resistance: primed tissues do not express full resistance levelsbut respond faster and stronger once they are attacked. Signalling that is mediated by volatilesadds significantly to the phenotypic plasticity in plant resistance expression and allows plants tosurvive in an ever-changing environment and in the unpredictable presence of its mobile enemies.