Observations on embryology of zygotes and early development of juvenile sporophytes inSargassum horneri

Abstract

In order to establish artificial seeding techniques of Sargassum horneri,it was observed in this paper the release of eggs,embryology of zygotes,development and growth of juvenile sporophytes,and effect of culture conditions on germlings growth in laboratory culture.The results showed that the eggs released simultaneously from the basal and middle parts of female receptacles,and adhered to the receptacle surface for fertilization and early development.After fertilization,eight nuclei in a newly released egg would rapidly start nuclei fusion to form a larger central nucleus and begin division.The zygote underwent two transverse divisions firstly,and produced a small named original cell which subsequently developed into rhizoids near the one extreme of the germling,meanwhile the other two cells of the germling developed into body of the juvenile sporophyte.After 48 hours,the zygote developed into a multicellular germling with rhizoid buds and began to fall and adhered to the attachment substance.After 15 days of culture,the germlings grew up to 3 mm in the mean length and with 2 leaflets.The higher temperature and longer daylength were of benefit to the growth and leaflet development of germlings.The germlings showed better growth at 21-24 ℃ under 40 μmol photons/(m2.s) and long-day(14L∶10D).