Morphogenic effect of colchicine in Cichorium intybus L. root explants cultured in vitro.

A simple and efficient protocol for in vitro shoot regeneration from storage root explants of witloof chicory (Cichorium intybus L.) has been used to study the effect of only colchicine at different concentrations, and colchicine in combination with kinetin or 2,4-D or with 2,4-D and kinetin, in comparison with only kinetin and control (no treatment), upon this type of morphogenic event. The results demonstrated a strong stimulatory effect of colchicine at low concentration on shoot regeneration frequency when compared to the number of shoots formed in the control. This effect was comparable to that of kinetin, a growth regulator that induces shoot differentiation. By contrast, the presence of 2,4-D completely inhibited shoot regeneration. Colchicine at high concentration did not induce shoots, and caused the complete death of the explants. A carefully histological analysis of the explants during the in vitro culture period showed the formation of numerous meristematic zones (precursors of adventitious bud and shoot development) in the parenchyma mass; these meristems were present only in the explants subjected to the colchicine and to the other treatments able to stimulate shoot differentiation. Nuclei of different sizes were observed in the explants treated with colchicine at low dose, the largest, probably, polyploids. Polyploid nuclei, in fact, were found in the regenerated plants.