Effects on Tritrophic Interactions

Leaf trichomes do not only affect herbivores, but also their natural enemies. This may indirectly affect the intensity of damage caused by herbivores. In theory, the effect on the abundance and effectiveness of natural enemies may be neutral (no effect), negative or positive (Fig. 4.1). If we assume that herbivores are affected negatively by leaf trichomes (Fig 4.1 top graph), a neutral effect on the third trophic level will result in natural enemies having an additive effect on plant damage...

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Brussels sprouts Brassica oleracea - large cabbage white Pieris brassicae - Cotesia glomerata Tobacco Nicotiana tabacum -moth Heliothis virescens Field elm Ulmus minor - elm leaf beetle Xanthogaleruca lutteola - Brussels sprouts plant becomes attractive to C. glomerata 30 minutes after caterpillar infestation, reaches a maximum after 3 hours and then remains constant for at least 14 hours Difference in volatile emission during day and night, influences night-active herbivores Twigs with a low...

Multidimensional space of realized fitness

Multidimensional Space

Fig. 3.4 Model of costs and benefits of induced defense in the multi-dimensional space of environmental conditions. Within this space, each plant genotype has a limited opportunity to realize a certain fitness level. The realized fitness of a genotype with increased resistance to one or more environmental stresses can be restricted under a variety of conditions. Fitness of genotype II (light gray) with increased anti-herbivores defense is lower than that of the less-defended genotype I (dark...

Metabolic Linkage

The difficulties of disentangling the fitness costs of allocating resources to a specific defense trait from the fitness consequences of shifts in allocation resulting from other processes activated during elicitation have already been mentioned. Furthermore, it is not clear whether in isogenic genotypes, disabled in the expression of a specific trait, the resources that are not used for defenses are redirected to be available for growth and reproduction. The resource allocation shifts required...

References

Adler LS, Karban R, Strauss SY (2001) Direct and indirect effects of alkaloids on plant fitness via herbivory and pollination. Ecology 82 2032-2044 Adler LS, Wink M, Distl M, Lentz AJ (2006) Leaf herbivory and nutrients increase nectar alkaloids. Ecol Lett 9 960-967 Agrawal AA (1999) Induced responses to herbivory in wild radish effects on several herbivores and plant fitness. Ecology 80 1713-1723 Agrawal AA (2001) Phenotypic plasticity in the interactions and evolution of species. Science 294...

Jasmonate Performs a Key Role in Systemic Wound Signaling

Despite significant progress in the identification of genes that regulate systemic defense responses, relatively little is known about the specific role of these components in the long-distance signaling pathway. In theory, genes required for the systemic response could play a role in production of the mobile signal, translocation of the signal from damaged to undamaged leaves, signal perception by target cells in distal leaves, or subsequent signaling steps leading to expression of target...

Resistance at the Plant Cuticle

Resistance against herbivores could potentially start at the plant cuticle, the first contact zone between an approaching organism and the plant. Due to its physico-mechanical and chemical properties the cuticle comprises several important physiological and ecological functions. Chemical compounds of or on the cuticle can directly act deterrent or even toxic to herbivores. The physico-mechanical cuticle characteristics influence locomotion and attachment of herbivorous insects but also of...

Induced Indirect Defense

Cuticular lipids can hold important functions in multitrophic interactions, as their major constituents can be chemically very similar between cuticles of plants, herbivores, and their predators. The cuticular lipid components of larvae of Manduca sexta L. Lepidoptera Sphingidae were shown to vary slightly depending on the surface composition of their specific host plants. This diet-related variation influences palatability by predatory ants Espelie and Bernays 1989 and thus indirectly plant...