Indirect defense strategy

Other aspects of implementing indirect volatile defenses, as recently discussed in several excellent reviews [17, 94, 95], will include the assessment of timing and synergy of volatile emissions with direct defense responses of the herbivore-damaged plant, especially if indirect defense strategies will be integrated with toxin-based pest control strategies. 

Pohnert G (2004) Chemical defense strategies of marine organisms. In Schulz S (ed) Chemistry of pheromones and other semiochemicals, vol 1. Springer, Berlin, pp 179-219 Pohnert G (2005) Diatom/copepod interactions in plankton the indirect chemical defense of unicellular algae. ChemBioChem 6 946-959... 

This additional lag time likely reduces the economic benefits of induction of indirect defenses relative to those of direct defense. Plants may have developed various strategies to minimize the lag time of indirect defense induction. Maintaining some baseline nectar production in undamaged plants could be such a strategy. By accommodating at least a few natural enemies, the indirect defense can begin to operate quickly once the plant is attacked. 

Figure 9.1. Different defense strategies of Nicotiana plants that evolved in response to herbivore attack. Besides a specialized germination-behavior that efficiently reduces the over-all number of potential herbivores, Nicotiana plants evolved the inducible nicotine synthesis as a direct defense and the inducible emission of volatiles to attract parasitoids of the herbivore as an indirect defense. A specialized defense mechanism is triggered in response to attack by the herbivore Mctduca sexta, adapted to Nicotiana plants. Attack results in an ethylene burst, which down regulates nicotine accumulation and results in a fundamental transcriptional re-organization within the plant.

A remarkable indirect strategy for chemical defense is found in embryos of the shrimp Palaemon macrodactylusy which are resistant to infection by the pathogenic fungus Lagenidium callinectesy a known pathogen of many crustaceans. This resistance is caused by bacteria on the surface of the embryos... 

These findings could point to new strategies needed in designing new antioxidant indole derivatives with superior capacity that could have an indirect beneficial effect on the human antioxidant defense system. 

The efforts for more efficient food production to feed the increasing human population require new and efficient, envirormientally sustainable and poUinator-friendly pest control strategies in crop plant protection. Terpenoids produced by crop plants or their companion plants could be one important tool to advance to that direction. Applications that minimize the harm for the environment and risk of development of resistant pest populations are needed. The principles of terpenoid-based natural indirect herbivore defense should be assessed more thoroughly to steer plant breeding to better include these properties in future cultivars. 

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