Systemic effects on oxidative enzymes in Phaseolus vulgaris leaves that have been wounded by the grasshopper Melanoplus differentialis (Thomas) or have had a foliar application of jasmonic acid

Fifteen-day-old intact primary leaves of Phaseolus vulgaris were either treated with 1 mM (-)-jasmonic acid (JA) or were wounded by fourth instar grasshoppers. Changes in protein content and the oxidative enzymatic activity of lipoxygenase-3 (lox-3), polyphenol oxidase (ppo), and peroxidase (pod) in both the trifoliate and primary leaves of the wounded plant were measured at 0, 24, 48, and 72 h using spectrophotometric methods. Results indicated that both JA treatment (at a higher rate) and wounding significantly enhanced total protein content in primary leaves at 24 and 48 h and induced systemic protein synthesis in trifoliate leaves up to 48 h. Insect wounding in primary leaves generally induced significant ppo, pod, and lox-3 activity throughout the 72 h, peaking at levels of 227% at 48 h, 56% at 72 h, and 37% at 24 h, respectively, compared to the control. In the trifoliate leaves of insect-wounded primary leaves, high systemic lox, ppo, and pod activity was sustained throughout the 72 h. In primary leaves treated with JA, lox and ppo generally maintained high activity up to 48 h. The pod activity, however, was suppressed throughout the 72 h. In the trifoliate leaves of JA-treated primary leaves, high lox activity was consistently retained throughout the 72 h, high ppo activity was maintained up to 48 h, and high pod activity was observed up to 24 h. In general, the effects of JA treatment and grasshopper wounding on enhanced protein synthesis and enzyme activity at the point of injury and on trifoliate leaves indicate that when wounded, signals are systemically mobilized.