Alternation of Generations of some Brown Algae in Unialgal and Axenic Cultures

Abstract

SEGI and KIDA, 1957;NAKAHARA and NAKAMuRA, 1973). Apospory of brown algae, the formation of a gametophyte from a vegetative cell of a sporophyte, was reported by KoRNMANN (1956) and NAKAHARA and NAKAMuRA (1973).In the past, drmculties in techniques of culture and of cytological observation have hampered the elucidation of the entire life cycle in culture and the alternation of nuclear phases.Therefore, major observations on the life cycles of brown algae have been made in the early stages of development of zoospores and zygotes.In the last thirty years, however, cultural techniques and equipment have improved and several species have been cultured from generation te generation in the laboratory.The favorable conditions for the growth and maturation have been revealed to some extent.Furthermore, morphological differences between sexual aRd asexual generations may reflect differences in metabolism, but our knowledge of this relationship is still insuffcient.According to KNIGHT (1931), the alternation between the macroscopic and microscopic phases in jEttoca7Pzts may be related to the availability of nitrates and phosphates.HsiAo (1969), studying Fletalonin, reported that the four asexual forms in its life cycle have differentiodiderequirernentsforgrowthanddevelopment.Recentiy,severalseaweedshave been cultured axenically by some investigators to study their nutritional requirements.However, these studies have dealt only with one of the two generations.With the obiect of clarifying the role of the environmental factors in the periodic expression of life forms and the alternation of generations in the brown algae, Icarried out cultural studies of selected species of Ralfsiales, Desmarestiales and Laminariales under the guidance of Prof. Y.