Terpenes of the Essential Oil from Ipomoea alba Leaf in Response to Herbivore and Mechanical Injuries

Abstract

There is no doubt that the chemical composition of plants, including norvolatile and volatile compounds, is widely affected by abiotic and biotic stress. Plants are able to biosynthesize a variety of secondary metabolites against actions of natural enemies, such as herbivores, fungus, virus and bacteria. The present study revealed that the chemical compositions of leaf essential oils from Ipomoea alba underwent quantitative and qualitative alterations both when infested with the grasshopper Elaeochlora trilineata and mechanically damaged. Grasshopper attack and mechanical wounding induced the biosynthesis of nine volatile compounds in leaves of I. alba: cumene, α-ylangene, β-panasinsene, β-gurjunene aromadendrene, β-funebrene, spirolepechinene, cubenol and sclareolide. The amount of germacrene D (33.2% to 20.4%) decreased when the leaves were mechanically damaged; but when the leaves were attacked by a grasshopper, the germacrene D increased from 33.2% to 39.4%. The results showed that I. alba leaves clearly responded to abiotic and biotic stress and contribute to an understanding of plant responses to stress conditions.