Abstract
Cichorium intybus L. (cv. Bea) root explants grown in continuous light had a higher fresh weight, lignin and chlorophyll content than explants grown in darkness. Intermediary values were found when the light conditions were switched after 6 days. Peroxidase activities (EC 1.11.1.7) were measured in the apoplastic fluid with guaiacol, indoleacetic acid (IAA) and syringaldazine as substrates. There was an inverse relationship between specific IAA oxidase activity and explant growth. Specific syringaldazine oxidase activity (SSO) correlated with the lignin content. Analysis by isoelectric focusing (IEF) showed that the apoplastic fluid contained both cationic and anionic peroxidase isoforms, whose expression differed according to culture conditions. Isoform isoelectric point (pI) 7.0 was only detectable when the explants were cultured for 12 days in darkness. When explants were grown for the first 6 days in light, SSO and lignin content were high and the isoforms pI 4.0, 6.6, 7.6 and 8.1 were highly expressed. Conversely, when the first 6 days were in darkness, specific IAA oxidase activity was high and the isoforms pI 4.5, 6.7 and 6.8. were most strongly expressed. The isoperoxidases pI 7.8 and 7.9 were strongly expressed when the explants were cultured for at least 6 days in darkness.
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