Studies On Sexual Reproduction And Photosynthesis Of Hizikia Fusiformis

Hizikia fusiformis (Harvey) Okamura (Sargassaceae,Phaeophyta) is an important economicbrown seaweed, being used as a healthy foodstuff, medical herb and marine vegetable in China,Japan and Korea. However, complete artificial seedling of Hizikia fusiformis has not yet beendeveloped. This experiment aimed to examine the effect of photoperiods on sexual reproduction,and different environment conditions on the physiologycal and biochemical characteristics ofHizikia fusiformis.The results showed that compared to the short light period, the long light period (L:D 15h:9h)has positive effects on the evolution of eggs, and fertilization success and the development ofzygotes. We proposed that incubating the parental mature Hizikia fusiformis under longerphotoperiod would be of benefit to the artificial seedlings via sexual reproduction. The results ofzygotes cultured in different environment conditions showed that low light intensity and 20℃had positive effect on zygotes growth and development. The experiment with zygotes beingtreated with different UV showed that zygotes had ability of resisting UVR.Thalli of Hizikia fusiformis were grown under different supplies of CO₂ and N. The resultsshowed that for the algae cultured under non-N-enriched seawater, elevated CO₂ concentrationhad nonsignificant effects on growth and biochemical traits. However, for the algae culturedunder N-enriched seawater, elevated CO₂ depressed the growth and photosynthesis, theconcentrations of soluble protein and soluble carbohydrate were also decreased. It was suggestedthat increased N supply together with the reduced pH resulted from the elevated CO₂concentration might lead to the accumulation of NO₂^-, which had toxic effect on Hizikiafusiformis. The results of the pxperiment with different tissues of Hizikia fusiformis whenemersed showed that photosynthesis of Hizikia fusiformis had ability of against slight water lose,but under the condition of severe water lost, photosynthesis of receptacles was significantlyinhibited, and it could hardly recover when re-subemersed.