DYNAMICS OF NITROGEN-COMPOUNDS IN THE CHICORY (CICHORIUM-INTYBUS L) TUBERISED TAP ROOT DURING THE GROWING-SEASON AND COLD-STORAGE PERIOD

Witloof chicory plants growing in the field were supplied with various amounts of nitrogen fertilizer as NH4NO3. Differences in N content of the root and biomass accumulation between N fertilized and non-fertilized plants appeared during the later stages of growth, between 80 and 190 days after sowing. Although the nitrogen content of the roots increased with increasing N supply the content of protein-N remained constant. The enhancement in N content of the roots was accounted for by the increase in amino acid content. About 85 % of the newly stored nitrogen was incorporated into amino acids and especially into arginine. The increase in the N content of the roots was associated with an increase in the dry matter (fructans) accumulation in the roots during the later stages of growth. After harvest, at the beginning of the cold-treatment period, proline content of the root was enhanced. After 2 months of cold-treatment protein hydrolysis took place in the root, leading to enhancement of amino acids and especially glutamine content.