DEVELOPMENT OF CALLUS-LIKE STRUCTURES AND PLANT-REGENERATION IN THALLUS SEGMENTS OF GRATELOUPIA-FILIFORMIS KUTZING (RHODOPHYTA)

Callus-like structures (CLS) were observed to develop from sectioned t issues of the thallus segments of Grateloupia filiformis Kutzing maint ained in Von Stosch enriched-seawater culture medium. Three types were observed: dark CLS originated from pigmented cortical cells, clear CL S and loose clear CLS both originated from colorless medullary cells. Dark and clear CLS developed from segments exposed to light while loos e clear CLS developed in darkness. Frequencies of different types of C LS varied according to the origin of the segments (apical, median and basal zones of primary branches). In order to assess the potential for plant regeneration, all CLS were isolated from the original segment a nd cultured under light. The potential for plant regeneration depends on the type of CLS and on the origin of the segments. The loose clear CLS and the CLS from apical segments produced the largest number of re generated plantlets. Cultures of CLS might be an effective system for micropropagation in G. filiformis and light seems to be an important f actor involved in mechanisms of plant regeneration.