Phenolic compounds and oxidative metabolism in green bean plants under nitrogen toxicity

The objective of the present work was to determine the effect of nitrogen t oxicity on the metabolism of phenolic compounds and of oxidative stress in Phaseolus vulgaris L. cv. Strike. The nitrogen was applied to the nutrient solution as NH4NO3 at 5.4, 10.8, 16.2, 21.6 and 27 mM. The results indicate that the application of 27 mM N can be defined as toxic, as it drastically depressed growth of the green bean plants in our experiment. In addition, the abiotic stress from the application of this N dosage inhibited the enzy mes polyphenol oxidase, peroxidase and catalase, and stimulated phenylalani ne ammonia-lyase and superoxide dismutase activities. The result was foliar accumulation of phenolic compounds and hydrogen peroxide (H2O2). The accum ulation of H2O2 also apparently caused a reduction in biomass production.