Lipid Peroxidation and Plant Tissue Disorders: Introduction to the Workshop

Abstract

Among the lipid peroxidation reactions, the addition of molecular O2 to polyunsaturated fatty acids (PUFAs) is of particular interest in biological systems. The lipoxygenase pathway is the most-studied enzymatic pathway for oxidizing PUFAs, but nonenzymatic reactions have also been characterized. When one considers the significance of lipid peroxidation, it is surprising to discover the many diverse areas that are affected. In fact, whether one considers the process beneficial or detrimental depends on the circumstances. In situations where lipid peroxidation has been implicated in tissue damage, controversy exists over whether it is involved in the primary events causing injury or merely a by-product. Lipid peroxidation is involved with normal developmental processes, including production of flavor and odor volatiles, formation of compounds with growth-regulator-like activities, and senescence. Characteristic flavors and aromas, such as those associated with cucumber (Cucumis sativus L.) and tomato (Lycopersicon esculentum Mill.), are due in part to the presence of various enzymes in the respective lipoxygenase pathways (Gardner, 1989). Although desirable characteristics may be imparted to foods by oxidized lipids, rancidity and other off-flavors can also develop (Perkins, 1989). Induced defenses, including the hypersensitive response associated with resistance to pathogens and herbivore defense involving proteinase inhibitors, rely in part on oxidation of PUFAs (Farmer and Ryan, 1992). These authors proposed that methyl jasmonate, formed from linolenic acid, may serve as a secondary messenger in the lipidbased signaling pathway. A direct role of aldehydes formed from PUFAs in inhibiting fungal growth also has been established (HamiltonKemp et al., 1992).