抄録
It is reported that long-day conditions induce receptacle formation of Sargassum
horneri grown in a laboratory-culture system. In this study, we
examined inductive effects of experimental day length on wild thalli of a
field population in receptacle formation. Materials (apical 5 cm segments of
plants) were sampled in a population with reproductive season in spring, and
every month from October to January when the population was in the rapid
vegetative growth stage. The segments were cultured under 4 photoperiod
regimes (8:16h, 10:14h, 12:12h and 14:10h L:D), 100 μmol photons m-2
s-1, 18-20 °C for 4 weeks and observed whether receptacles were
formed or not.
October material was young and did not form receptacles under all
photoperiod regimes during the experiment. However, November material formed
receptacles under longer-day conditions, that was 100 % and 50 % in
frequency under 14:10h and 12:12h L:D, respectively. Receptacle formation
of December material was also promoted in longer day length, and
no segments became reproductive under 8:16h L:D. January material formed
receptacles under all photoperiod regimes, which indicated that plants in
January had been already triggered for reproduction in the field. Though
factor (s) triggering re-production of S. horneri in the
field is still unclear, artificial long-day conditions are effective to
induce receptacle formation on wild thalli in the vegetative growth stage.
