• defence;
  • herbivore;
  • light;
  • pathogen;
  • resistance;
  • tolerance


  •  Summary 677

  • I. 
    Introduction 678
  • II. 
    Light as an environmental variable 678
  • III. 
    Long-term effects of light on plant–herbivore or plant–pathogen interactions 679
  • IV. 
    Mechanisms of responses to the light environment: the whole-plant perspective 684
  • V. 
    Short-term responses to the light environment: induced defences 686
  • VI. 
    Mechanisms for light-dependent induced defences 688
  • VII. 
    Interpreting interactions between light and defence responses 690
  •  Acknowledgements 693

  •  References 693


Plants frequently suffer attack from herbivores and microbial pathogens, and have evolved a complex array of defence mechanisms to resist defoliation and disease. These include both preformed defences, ranging from structural features to stores of toxic secondary metabolites, and inducible defences, which are activated only after an attack is detected. It is well known that plant defences against pests and pathogens are commonly affected by environmental conditions, but the mechanisms by which responses to the biotic and abiotic environments interact are only poorly understood. In this review, we consider the impact of light on plant defence, in terms of both plant life histories and rapid scale molecular responses to biotic attack. We bring together evidence that illustrates that light not only modulates defence responses via its influence on biochemistry and plant development but, in some cases, is essential for the development of resistance. We suggest that the interaction between the light environment and plant defence is multifaceted, and extends across different temporal and biological scales.