Résultat de la recherche
Soil salinization effects on volatile signals that mediate the induction of chemical defenses in wild cotton
Plants respond to complex blends of above- and below-ground volatile organic compounds (VOCs) emitted by neighboring plants. These responses often involve priming (i.e., preparation) or induction (i.e., increase) of defenses by “receiver” plants upon exposure to VOCs released by herbivore-damaged neighboring “emitters.” However, recent work has shown that induc- tion of VOC emissions by herbivory is modulated by abiotic factors, potentially affecting plant–plant signaling. We tested the effect of soil salinization on the induction of VOC emissions in wild cotton (Gossypium hirsutum) due to leaf damage and its consequences for the induction of defenses in neighboring plants. To this end, we performed a greenhouse factorial experiment where emitter plants were subjected to augmented soil salinity (vs. ambient salinity) and within each group emitter plants were subsequently exposed to simulated caterpillar damage (mechanical leaf damage treated with Spodoptera frugiperda oral secretion) or no damage (control). After 48 h of exposure, we collected VOCs released by emitter plants and then damaged the receivers and collected their leaves to measure levels of chemical defenses (terpenoid aldehydes of known insecticidal effects). We found an interaction between leaf damage and salinization for two groups of VOCs released by emitters (sesquiterpenes and other aromatic compounds), whereby damaged receivers had higher emissions than control plants under ambient but not salinized soil conditions. We also found that, upon being damaged, receiver plants exposed to damaged emitters exhibited a significantly higher concentration of heliocides (but not gossypol) than control plants. However, salinization did not alter this VOC exposure effect on receiver induced responses to damage. Overall, we show that exposure to induced VOC emissions from damaged plants magnifies the induction of chemical defenses due to leaf damage in neigh- boring individuals and that this is not contingent on the level of soil salinity despite the latter's effect on VOC induction.
Soil salinization disrupts plant–plant signaling effects on extra-floral nectar induction in wild cotton
Plant–plant interactions via volatile organic compounds (VOCs) have received much attention, but how abiotic stresses affect these interactions is poorly understood. We tested the effect of VOCs exposure from damaged conspecifics on the production of extra-floral nectar (EFN) in wild cotton plants (Gossypium hirsutum), a coastal species in northern Yucatan (Mexico), and whether soil salinization affected these responses. We placed plants in mesh cages, and within each cage assigned plants as emitters or receivers. We exposed emitters to either ambient or augmented soil salinity to simulate a salinity shock, and within each group subjected half of the emitters to no damage or artificial leaf damage with caterpillar regurgitant. Damage increased the emission of sesquiterpenes and aromatic compounds under ambient but not under augmented salinity. Cor- respondingly, exposure to VOCs from damaged emitters had effect on receiver EFN induction, but this effect was contingent on salinization. Receivers produced more EFN in response to damage after being exposed to VOCs from damaged emitters when the latter were grown under ambient salinity, but not when they were subjected to salinization. These results suggest complex effects of abiotic factors on VOC-mediated plant interactions.