Oxidative and Molecular Responses in Capsicum annuum L. after Hydrogen Peroxide, Salicylic Acid and Chitosan Foliar Applications.

Hydrogen peroxide (H₂O₂) is an important ROS molecule (Reactive oxygen species) that serves as a signal of oxidative stress and activation of signaling cascades as a result of the early response of the plant to biotic stress. This response can also be generated with the application of elicitors, stable molecules that induce the activation of transduction cascades and hormonal pathways, which trigger induced resistance to environmental stress. In this work, we evaluated the endogenous H₂O₂ production caused by salicylic acid (SA), chitosan (QN), and H₂O₂ elicitors in Capsicum annuum L. Hydrogen peroxide production after elicitation, catalase (CAT) and phenylalanine ammonia lyase (PAL) activities, as well as gene expression analysis of cat1, pal, and pathogenesis-related protein 1 (pr1) were determined. Our results displayed that 6.7 and 10 mM SA concentrations, and, 14 and 18 mM H₂O₂ concentrations, induced an endogenous H₂O₂ and gene expression. QN treatments induced the same responses in lesser proportion than the other two elicitors. Endogenous H₂O₂ production monitored during several days, showed results that could be an indicator for determining application opportunity uses in agriculture for maintaining plant alert systems against a stress. [ABSTRACT FROM AUTHOR]