Studies On Techniques Of Sargassum Fusiforme Egg Preservation And Its Response To Salt Stress

With the shortage of wild resources of Sargassum fusiforme and the increasing market demand,large-scale artificial cultivation of S.fusiforme has become an inevitable trend,and it also brings many production problems.In order to achieve the preservation of superior strains of S.fusiforme and cross-regional transport culture,and to assess the effects of seawater salinity changes on the growth of S.fusiforme seedlings.In this study,S.fusiforme fertilized eggs were used and preserved by using two preservation schemes,low and ultra-low temperature.The analysis of different cryoprotectants was optimized to obtain better cryopreservation methods and cryoprotectants.At the same time,the photosynthetic response characteristics of S.fusiforme seedlings to different seawater salinity gradient stresses were studied,which provided technical support and theoretical reference for artificial breeding of S.fusiforme.The main findings are as follows:1?The best effect of cryoprotectant is:seawater+0.01M HEPES+10%DMSO.At 4?,low temperature inhibited and slowed down the generation of pseudotrophs in S.fusiforme fertilized eggs,while S.fusiforme fertilized eggs were not suitable for prolonged refrigeration at4?.The survival rate and mortality rate of S.fusiforme fertilized eggs increased substantially after 24 h of refrigeration,and the Rhizoid rate of S.fusiforme fertilized eggs reached its maximum.When the refrigerated time reached 72 h,the mortality rate of S.fusiforme fertilized eggs reached 90%after 48 hours of culture.When the conventional freezing procedures is used to save S.fusiforme fertilized eggs,reagent??seawater+0.01M HEPES+10%DMSO?and reagent??seawater+0.01M HEPES+10%DMSO+10%Sorbitol?have better preservation effect on S.fusiforme fertilized eggs.After 7 days of resuscitation,the survival rate reaches about 15%;The vitrification preserves the S.fusiforme fertilized eggs,and the reagent?is more effective in preserving S.fusiforme fertilized eggs,the survival rate of S.fusiforme fertilized eggs can reach 20%after 7 days of resuscitation.At the same time,cryopreservation of ultra-low temperature is inevitable to freeze damage of S.fusiforme fertilized eggs.The growth and development of S.fusiforme fertilized eggs preserved by vitrification is better than conventional freezing procedures.2?Photosynthesis of S.fusiforme was significantly affected by excessive low-and high-salinity stress.Specifically,at salinity of 20‰,the photosynthesis of S.fusiforme seedlings was slightly affected,which indicating low salinity tolerance in S.fusiforme seedlings.However,the very low salinity level?15‰?significantly depressed algal photosynthesis.At high salinity of 45‰,S.fusiforme seedlinds were damaged by high salt stress,its photosynthetic activity and utilization of inorganic carbon were significantly inhibited.While the effects of salt stress were different during prolonged culture.In a short time treatments,the seedlings photosynthesis was less affected,and itse pigment contents?Chl-a,Chl-c,Car?,photoelectron transfer rate(r ETR_max),and light energy utilization efficiency?F_v/F_m?exhibited changes of decreasing followed by increase.In prolonged culture,excessive low-?15‰?or high-salinity?45‰?significantly inhibited algal photosynthesis,meaning notable decreasing of its r ETR_max,effective photochemical efficiency???,the maximum photosynthetic rate?P_m?,and V_max.Moreover,excessive high salinity stressed the photosynthesis process of S.fusiforme seedlings by hindering the synthesis of its photosynthetic pigments.The above results indicate that the S.fusiforme fertilized eggs are relatively fragile,and the reagent?used for cryopreservation is better as a cryoprotective substrate for preservation.The freezing damage should be considered to the S.fusiforme fertilized eggs;The storage of S.fusiforme fertilized eggs at 4?should be controlled within 24 h,and the ultra-low temperature storage should use the vitrification for cryopreservation.;It indicated that,the strategies for preventing low-and high-salinity stress on S.fusiforme seedlings should be practically performed when the salinity levels extremely changed,to avoid the severe stress of prolonged salinity change on the seedlings.