CALLUS INDUCTION AND THALLUS REGENERATION OF THE RED ALGA MERISTOTHECA-PAPULOSA (RHODOPHYTA, GIGARTINALES)

Suitable medium and culture conditions for callus induction from thall us explants and thallus regeneration in the red alga Meristotheca papu losa (Montagne) J. Agardh were examined. Axenic explants were obtained by treatment of thallus segments in iodine solution followed by an an tibiotic mixture. The highest level of callus induction from axenic ex plants vc as obtained on ASP12NTA medium with 1.5% agar incubated at 2 0 degrees C temperature and a photon flux density of 10 mu mol photons m(-2) s(-1). The callus was induced mainly from the cortical and medu llary tissues at the cut surface and the callus cells were red pigment ed. The callus cells were ellipsoidal or spherical and in the initial stages the cells were uniseriate, with time the callus grew irregularl y. The callus induction rate was influenced by thallus collection time . The explants from thalli collected during December-May showed a high er rate of callus induction than the June-July collections. Addition o f 0.1 mg L(-1) indole-3-acetic acid (IAA) in combination with 0.05 mg L(-1) 6-benzylaminopurine (BAP) was effective in enhancing the callus size, but not the induction rate. Sucrose was most effective carbon co mpound tested, enhancing callus induction rate and size. Glycerol, man nitol and sorbitol showed an inhibitory effect. The excised callus fro m the explant showed sustained growth on subculture. The callus mass f ormed shoots when transferred to aerated PES liquid medium in 2-3 week s. At 20 or 25 degrees C, 40 mu mol photons m(-2) s(-1) were favourabl e for shoot formation. In 3 months these shoots regenerated 4.5 cm lon g thallus.