ABSTRACT
Plants respond to biotic or abiotic stress with a wide range of mechanisms that involve the production of multiple natural products, also known as secondary metabolites, having diverse roles and biological activities. Phytoalexins are secondary metabolites produced de novo by plants in response to stress, including microbial attack, intense heat, or UV radiation (Bailey and Manseld, 1982). That is, phytoalexins are not present in naturally healthy plant tissues but their primary precursors are recruited into the phytoalexin biosynthetic pathway upon elicitation by an exogenous stimulus. The ecological signicance and defensive roles of phytoalexins have been widely demonstrated in various plant families and are not the subject of this review, as several general reviews dealing with these aspects have appeared over the past 20 years. In contrast to phytoalexins, phytoanticipins are constitutive antimicrobial metabolites whose concentration may increase when the plant is under stress (VanEtten et al., 1994).
