ABSTRACT
Conifers are an ancient, yet successful, group of plants, well adapted to harsh environmental conditions. Conifers possess unique physical and chemical defenses that help them overcome fungal and insect attacks. Oleoresin, a major component of this defense is a complex mixture of terpenoids, mainly composed of volatile monoterpenes (turpentine) and nonvolatile resin acids (rosin). These water-insoluble toxic phytochemicals are biosynthesized and stored in specialized anatomical structures. This chapter discusses the biochemical mechanisms by which constitutive and induced oleoresin are formed. In many conifers, the levels of monoterpenes and diterpenoid resin acids present in wounds are higher than in control (nonwounded) tissues and, in many instances, fungal infection causes further accumulation of oleoresin compared with aseptic wounds. To test the hypothesis that ethylene is involved in monoterpene biosynthesis in grand fir, and to further assess individual tree-to-tree variation in this response, grand fir saplings were either wounded, or wounded and treated with ethrel, a chemical that releases ethylene.
