Induced production of extrafloral nectar in intact lima bean plants in response to volatiles from spider mite-infested conspecific plants as a possible indirect defense against spider mites

Abstract

We found that intact lima bean plants increased the secretion of extrafloral nectar (EFN) after exposure to Tetranychus urticae-induced plant volatiles. Predatory mites, Phytoseiulus persimilis, dispersed more slowly from an exposed intact plant than from a control plant (plant exposed to volatiles from intact conspecific). The predators also dispersed more slowly from those plants that were provided with extra EFN than from untreated plants. We further show that EFN was a potential alternative food source for P. persimilis. From these results, we concluded that increased EFN was involved in the slow dispersal of P. persimilis from the plants exposed to herbivore-induced plant volatiles. Our data suggest that the increase of EFN in an HIPV-exposed intact plant could be an induced indirect defense against spider mites.

Within-plant signaling by volatiles leads to induction and priming of an indirect plant defense in nature

“…Can VOCs serve as a means of within-plant signaling? Because earlier studies showed that VOCs induce and prime EFN secretion in undamaged lima beans (31,33,34) we focused on EFN secretion, which was quantified in all experiments 24 h after starting the induction of the emitter leaves as amounts of soluble solids per leaf dry weight.…”

Chemical Defence and Toxins of Plants

“…159 This increased attractiveness was explained by the fact that uninfested lima bean leaves that were exposed to volatiles from infested conspecific leaves could adsorb the volatiles and re-emit them. 161 Choh et al 136 further reported that HIPV-exposed intact plants produced more EFN compared to control plants (plants exposed to volatiles from intact plants). It remains unanswered how the mechanisms involved in the production of components of EFN differ between infested plants and HIPV-exposed plants.…”

“…The components of EFN have been reported in several plant species. For example, Choh et al 136 reported EFN of lima bean plants contained fructose, glucose, and sucrose as major sugars. Interestingly, T. urticae-infested lima bean plants contained smaller amounts of sucrose and larger amounts of fructose in EFN than uninfested plants.…”

Duration of Priming of Two Indirect Plant Defenses

“…4 For exposure of plants to HIPVs, we used a 60 x 60 x 60 cm cage with two 30 x 30 cm windows on opposite sides of the cage. 12 As odor sources, we used eight plants that had been infested with 60 adult T. urticae females per plant for 1 day. Eight uninfested plants were used as control odor sources.…”