Rot. Mag. ~rokyo 84: 435--437, 1971 Short Communication Some Differences in Nutritional Requirements between Different Generations in Brown Algae, Desmarestia HIRO YUKI NAKAHARA* and MASAKAZU TATEWAKI Institute of Algological Research Faculty of Science, Hokkaido University, Muroran 051 The members of the Desmarestiales have life histories involving the alternation of a macroscopic sporophyte and a microscopic gametophyte with oogamous reproduc- tion (Schreiber, 1932 ; Kornmann, 1962 ; Nakahara and Nakamura, 1971). The morphological differences between the generations may be partly based on differences in their metabolism, but our knowledge of these problems is still insufficient. Recently some kinds of brown algae have been cultured axenically and their nutritional requirements have been studied by several investigators (Boalch, 1961; Pedersen, 1969a, 1.969b). These studies, however, have concerned only one generation of the life cycle. Pure cultures of gametophytes of Desmarestia viridis (Mull.) Lamour, and Desmarestia ligulata (Lightf.) Lamour. were obtained by isolating single zoospores with a micropipette and transferring them to sterilized media. The gametophytes of both species grew well in ASP12 medium of Provasoli (1963) at 14° with a 14-hr photoperiod, but the plants remained sterile. They became fertile and produced sporophytes when transferred to an environment of 10° with a 10-hr photoperiod. At 10° with a 14-hr photoperiod, the pseudo-parenchymatous sporophytes of D. viridis grew well, normally in ASP12. On the other hand, those of D. ligulata did not develop into normal thalli but formed masses tangled with branches and corticating threads. Nearly normal sporophytic thalli were obtained, however, when 20 or 100 mg glucose was added to 100 ml of ASP12 medium. This observation prompted a more extensive study of the morphogenetic effects of organic supplements on plants of Desmarestia. We therefore examined the effects of various carbohydrates and organic acids on the growth of gametophytes and sporophytes of D. viridis and D. ligulata. The responses to glucose, sodium acetate and pyruvic acid were especially interesting, since they were different in the two phases of the life history. The observations are shown in Tables 1 and 2. Such observations may provide clues to metabolic differences controlling their differentiation. This work was supported partly by a grant from the Ministry of Education of Japan. We wish to acknowledge the advice and encouragement given by Professor * Present Address: Department of Fisheries, Faculty of Agriculture, Kyoto University, Maizuru 625. 436 HI. 1VAKAHARA and M. TATEWAKI Vol. 84 Table 1. Effects of organic supplements on growth of gametophyte and sporophyte in D. viridis. Table 2. Effects of organic supplements on growth of gametophyte and sporophyte in D, ligulata. Y. Nakamura, and the help of Professor R.A.. Lewin, Scripps Institution of Oceano- grapy, University of California, in the preparation of this paper. References BOALCH, G.T. 1961. Studies on Ectocarpus in culture. II. Growth and nutrition of a bacteria- free culture. J. Mar. Biol. Ass. UK. 41: 287-304. KORNMANN,P. 1962. Der Lebenszyklus von Desmarestia viridis. Helgol. Wiss. Meeresunters 8(3) : 287--292. NAKAHARA, H. AND Y. NAKAMURA. 1971. The life history of Desmarestia tabacoides Okamura. Bot. Mag. Tokyo 84: 69-75. PEDERSEN, M. 1969a. The demand for iodine and bromine of three marine brown algae grown in bacteria-free culture. Physiol. Plant. 22: 680-685. 1969b. Marine brown algae requiring Vitamin B12. Physiol. Plant. 22: 977-983. PROVASOLI, L. 1963. Growing marine seaweeds. In : Proc. IVth Seaweed Symp., 1961: 9-17 Pergamon Press, New York. SCHREIBER, E. 1932. Uber die Entwicklungsgeschichte and die systematische Stellung der Desmarestiaceen. Zeitschr. Bot. 25: 561-582. Received October 8, 1971 Nutritional Requirements in Desmarestia 437 .