Pith elongation in chicory (Cichorium intybus L.) heads: influence of light breaks and daminozide

During production of Belgian endive, the stem (pith, core) can elongate in the center of the chicory head. Pith formation in the chicory head is respo nsible for down-grading the product, lowering its market value. Two treatme nts influencing pith elongation were studied. White-light-breaks of differe nt durations were applied at different periods during hydroponic forcing. F our light breaks each of 5 min white light spread evenly over 12 h per day halved relative pith length without influencing chicory head length and wit h limited greening of the leaf tissue. Application of the gibberellin biosy nthesis inhibitor daminozide in the nutrient solution caused a reduction in relative pith length, but also reduced chicory head elongation. Although t hese treatments are not usable in practise, they are very interesting to st udy the possible interaction between phytochrome and gibberellin metabolism in the control of chicory stem elongation. (C) 1999 Elsevier Science B.V. All nights reserved.