Effects Of Environmental Factors On The Growth Biochemical Components And Nitrogen Absorpion Of Sargassum Horneri

In recent years,with the increasingly frequent human activities and the massive discharge of industrial waste water,the marine ecological environment has been deteriorated severely,and the seaweed farm has experienced a large area decline and the natural resources of Sargassum horneri have been declining.The economic value and ecological value of Sargassum horneri continue to be developed,leading to the shortage of Sargassum horneri.In addition,as a kind of large algae,Sargassum horneri has a biological purification effect on eutrophication water,which can alleviate the environmental problems such as eutrophication and red tide.Therefore,it is urgent to carry out the research on the cultivation of Sargassum horneri.In this paper,by studying appropriate environmental conditions of different growth stages of Sargassum horneri,the optimum salinity of accumulation of biochemical components and the absorption of nitrogen under the stress of nutrients deficiency,aimed at providing theoretical guidance for artificial breeding and ecological applications of Sargassum horneri.The main findings as follows:1.We evaluated the growth and pigment content of receptacles of Sargassum horneri in different environments.The results showed that?1?The highest RGR of length were observed in receptacles cultured under100?mol/?m²·s?,20-25?,salinity 25‰and N/P 50:1.When the N/P ratio was 1:1,it was beneficial to the widening of the receptacles.?2?The highest pigment content were observed in receptacles cultured under15-20?and salinity 30‰-35‰,and the higher temperature?such as25??is not conducive to the accumulation of pigment.When the light intensity was 50?mol/?m²·s?,the content of photosynthetic pigment was the highest,and the weaker light contributed to the accumulation of pigment in Sargassum horneri.When concentration of nitrogen was at8mg/L and the ratio of nitrogen to phosphorus was 1:1,the receptacles had more pigment.When the concentration of phosphorus is at 0.4mg/L,the higher concentration of nitrogen,the more the pigment accumulated.Culture media that was rich in nitrogen or phosphorus had a beneficial effect on the accumulation of pigment.2.Using NaNO₃ and KH₂PO₄ as the sources of nitrogen and phosphorus,the effects of different concentrations and ratios of nitrogen and phosphorus on the growth of Sargassum horneri seedlings were studied.The results showed that the effects of nitrogen and phosphorus on the growth of Sargassum horneri seedlings were significant?P<0.01?.And RGR was the highest when the concentrations of nitrogen and phosphorus were 8mg/L and 0.4mg/L respectively.The interaction had no significant effect?P>0.05?.And nitrogen with different mass concentrations was the main effect?P<0.01?.Different N/P ratio had significant effect?P<0.01?.When the N/P ratio was 10:1,the specific growth rate of Sargassum horneri seedlings was the highest.3.By measuring the growth and biochemical properties of Sargassum horneri at different salinities,I found that Sargassum horneri grew well in the salinity range of 25‰-30‰,which was significantly different from other groups?P<0.05?.When the salinity was 35‰,the soluble protein content was the highest?1.3mg/g?.When the salinity was below or above 35‰,the content of soluble protein both were decreased.When the salinity was 30‰,the contents of chlorophyll a and chlorophyll c were the highest.The content of carotenoid was the highest at 35‰and no significant difference with 30‰and 40‰?P>0.05?.When the salinity was 30‰,the soluble sugar in Sargassum horneri was accumulated in a large amount,and the content reached 3.163mg/g,which was four times higher than that group of 0‰.The analysis of the trends of growth and biochemical composition showed that there was a critical salinity value.Greater or less than the critical salinity value,the growth and biochemical composition would show a downward trend.4.After nutrition restriction stress for 10 days,evaluating the absorption rate of NH₄-N and NO₃-N of Sargassum horneri among the three days which was restored to nutrition.After subject to the nutrients deficiency,Sargassum horneri showed a strong ability of NH₄-N uptake.On the first day of the recovery of nutrition culture,the uptake rate of NH₄-N of the starved group was the highest at 14.94?mol/?g·h?,which was significantly different from the control group and the fed group.The difference between the control group and the treatment group decreased gradually,and the absorption rate of each group tended to be same on the third day.But the absorption rate of NO₃-N of each group was relatively small,up to 6.15?mol/?g·h?.When nitrogen sources included NH₄-N and NO₃-N,Sargassum horneri preferentially absorbed NH₄-N.The growth rate measured after the experiment confirmed the phenomenon of over-compensatory growth in Sargassum horneri.