Study On The Early Development Of Three Macroalgae Species

Studies on the early development of sporelings from carpospores of Gracilaria asiatica Chang et Xia and Chrysymenia wrightii (Harvey) Yamada was conducted indoors under controlled culture conditions. The normal development process of carpospores of two red seaweeds were comprised of three stages: division stage, basal disc stage and sporeling stage, which were in accord with the typical development characteristics of common red seaweeds. The coalescence of basal discs were both found, and the number of coalescenced basal discs was higher in C. wrightii than in G. asiatica.Besides normal development of sporelings, a new developmental phenomenon of filamentous frond was both observed for two red seaweeds. It was composed of one or two rows of cells, and took place from the outmost brim of the basal disc. During the early disc stage of germinated carpospores, one or two filamentous fronds formed on about 10% basal discs. Lately more filamentous fronds appeared from the brims of up to 80% basal discs. Meanwhile one or more upright fronds protuberated on the basal discs. Generally, filamentous fronds exhibited in self-existence or co-existence forms with the normal young sporelings on the same basal disc, and single cell detached from filamentous fronds developed into a new filamentous frond. This new phenomenon exhibited a unique differentiated pathway during the early development of G. asiatica and C. wrightii, which would be potential for the application in artificial sporelings nursery.Temperature (10, 15, 20, 25℃) and irridance variations (8 and 36μmol photons m-2 s-1) significantly influenced the germination rate of carpospores and the diameter of discs of C. wrightii, 15～25℃under 36μmol photons m-2 s-1 were the feasible conditions for germination of carpospores, the maximum growth of discs occurred 25℃and 36μmol photons m-2 s-1, 10℃and 8μmol photons m-2 s-1 were unfavourable for the germination of carpospores and the growth of discs.Morphology and culture studies on germlings of Sargassum thunbergii (Mertens et Roth) Kuntze were also carried out under controlled laboratory conditions. The results showed that temperature variations (10, 15, 20, 25℃) under 88μmol photons m-2 s-1significantly influenced the growth rate within the first week of the experiment, although this effect became less obvious after eight weeks, especially under temperatures of 15 and 20℃. Variation in germling growth was highly significant under different levels of irradiance (9, 18, 44, 88μmol photons m-2 s-1) at 25℃. Growth of germlings cultured under blue light was lower than in white light.