Effect of NAA on the development, apoplastic peroxidase activities, and peroxidase isoenzymes in chicory root explants

NAA significantly modified the growth of chicory (Cichorium intybus L. cv. Bea) root explants cultured for 12 d in either light or darkness. It also reduced the chlorophyll and the lignin content, peroxidase (EC 1.11.1.7) activities such as guaiacol peroxidase, auxin oxidase, and syringaldazine peroxidase in light as well as in darkness. There was a positive relationship between specific syringaldazine peroxidase activity and the lignin content, as well as between anionic peroxidases and lignification. Conversely, specific IAA oxidase activity and fresh weight were negatively correlated. NAA enhanced the expression of cationic peroxidase isoenzymes, particularly a peroxidase isoform pI 8.9 (Cicpx), in darkness and in light. This Cicpx was not involved in the lignification process. NAA is suggested as exerting an inhibitory effect on the biosynthetic pathways of tetrapyrrole-containing compounds.