CHELATED IRON AND GAMETOGENESIS IN MACROCYSTIS

Stekoll, M. S. Juneau Center for Fisheries and Ocean Sciences, University of Alaska, Juneau, AK 99801 USA Gametophytes of Macrocystis can be vegetatively propagated indefinitely in the laboratory in media that lacked chelated iron. When clones of vegetatively propagated female gametophytes of Macrocystis pyrifera (L.) C. Ag. were exposed to varying levels of chelated iron in both enriched natural and artificial seawater, low levels of chelated iron (1-5 micromoles/liter) stimulated the onset of gametogenesis as measured by egg production. In contrast higher iron concentrations strongly inhibited egg production. Gametophyte growth as measured by the increase in cell number was not affected by iron concentration in the medium. At all iron concentrations there was a tendency for the larger gametophytic fragments to become fertile earlier. The results suggest that iron may play a critical role in the development of Macrocystis gametophytes.