caryophyllene and 3-hexenylacetate

Tomato plants respond to herbivory by emitting volatile organic compounds (VOCs), which are released into the surrounding atmosphere. We analyzed the tomato herbivore-induced VOCs and tested the ability of tomato receiver plants to detect tomato donor volatiles by analyzing early responses, including plasma membrane potential (V(m)) variations and cytosolic calcium ([Ca²⁺](cyt)) fluxes. Receiver tomato plants responded within seconds to herbivore-induced VOCs with a strong V(m) depolarization, which was only partly recovered by fluxing receiver plants with clean air. Among emitted volatiles, we identified by GC-MS some green leaf volatiles (GLVs) such as (E)-2-hexenal, (Z)-3-hexenal, (Z)-3-hexenyl acetate, the monoterpene α-pinene, and the sesquiterpene β-caryophyllene. GLVs were found to exert the stronger V(m) depolarization, when compared to α-pinene and β-caryophyllene. Furthermore, V(m) depolarization was found to increase with increasing GLVs concentration. GLVs were also found to induce a strong [Ca²⁺](cyt) increase, particularly when (Z)-3-hexenyl acetate was tested both in solution and with a gas. On the other hand, α-pinene and β-caryophyllene, which also induced a significant V(m) depolarization with respect to controls, did not exert any significant effect on [Ca²⁺](cyt) homeostasis. Our results show for the first time that plant perception of volatile cues (especially GLVs) from the surrounding environment is mediated by early events, occurring within seconds and involving the alteration of the plasma membrane potential and the [Ca²⁺](cyt) flux.

Topics: Acetates; Aldehydes; Animals; Bicyclic Monoterpenes; Calcium; Cell Membrane; Cytosol; Ecosystem; Gas Chromatography-Mass Spectrometry; Herbivory; Host-Parasite Interactions; Membrane Potentials; Monoterpenes; Moths; Plant Leaves; Polycyclic Sesquiterpenes; Sesquiterpenes; Signal Transduction; Solanum lycopersicum; Spodoptera; Time Factors; Volatile Organic Compounds

Natural enemies of herbivorous insects utilize numerous chemical cues to locate and identify their prey. Among these, volatile plant compounds produced after attack by herbivores may play a significant role (hereafter herbivore-induced plant volatiles or HIPVs). One unresolved question is whether the composition of the volatile cue blends induced by different herbivore species differ consistently enough to indicate not only that the plants are damaged by herbivores but also the identity of the herbivore species causing the damage. We studied HIPV production in the undomesticated plant species Datura wrightii in the laboratory when damaged by either of two leaf-chewing herbivore species, Lema daturaphila or Manduca sexta, or when damaged by L. daturaphila and the piercing-sucking bug, Tupiocoris notatus, or both L. daturaphila and T. notatus, for 24 hr. HIPV production was monitored 1 d before induction, the day of induction, and for 7 d after induction. In all experiments, both the quantities and composition of the HIPV blends varied with the time since induction as different components reached peak production at different times after induction. HIPV blends did not differ consistently with the herbivore species causing the damage. For plants damaged by both L. daturaphila and T. notatus, greater amounts of HIPVs were produced than by plants damaged by either species alone, but the amounts did not differ from that predicted as the sum from damage inflicted by each herbivore species independently. The HIPVs of D. wrightii are a general rather than specific indicator of damage by herbivores. Because generalist predators are the most abundant natural enemies in this system, general cues of herbivore damage may be all that are required to facilitate the discovery by predators of plants damaged by any of several suitable prey species.

Topics: Acetates; Alkenes; Animals; Datura; Insecta; Plant Leaves; Polycyclic Sesquiterpenes; Sesquiterpenes; Species Specificity; Terpenes; Time Factors; Volatile Organic Compounds