Cotton volatiles synthesized and released distal to the site of insect damage

Cotton plants (Gossypium hirsutum) damaged by herbivorous insects release volatile compounds that act as chemical signals to attract natural enemies of the herbivore to the damaged plant. Feeding by beet armyworm larvae (Spodoptera exigua) on the lower leaves of cotton plants triggers the systemic release of six readily detectable terpenes and hexenyl acetate, a product of the lipoxygenase pathway. Labelling with ¹³CO₂ established that the terpenes released systemically after herbivore damage are synthesized de novo at or near the site of emission. Hexenyl acetate rapidly incorporated ¹³C into the acetate but not into the hexenyl moiety within our pulse labelling interval. Thus, activation of the lipoxygenase pathway in undamaged leaves of insect damaged plants is indicated.