THE LIFE-CYCLE OF PORPHYRA TENERA IN VITRO

Abstract

Chemically defined media or enriched seawater support good growth of the Conchocelis and thallus phases of unialgal P. tenera. The Conchocelis phase grows well free in liquid media; a calcareous substrate is unnecessary. The Conchocelis phase was cultured for one year in continuous fluorescent light by transferring free colonies or pieces of filaments every 2 months in new media. Monosporangia formation and release of fertile monospores are induced by short-day conditions (8-11 hours daily). The leafy thallus, derived from monospores, is a short-day plant. A photoperiod of 13 hours daily inhibits growth of young thalli: the thalli bleach, produce big, dark-pigmented cells which produce spores germinating into Conchocelis filaments. Under long-day conditions the thalli while degenerating, can also produce rhizoid-like structures which give rise to Conchocelis filaments. The photoperiod governs, besides growth, the formation of the spores producing the next phase of the life-cycle: short-day for monospores; long-day for carpospores. Under opportune photoperiod conditions the complete life-cycle can be obtained in five months.