The Response Of Gracilaria Lemaneiformis To Environmental Stress And Its Preliminary Application In Medicine

Gracilaria lemaneiformis(Gracilaria,Rhodophyta) is one of the important economic seaweeds.Featuring advantages such as rapid growth,high uptake of the nutrients nitrogen(N) and phosphorus(P),Gracilaria lemaneiformis has been suggested to be a promising plant to remediate the ecological environment in eutrophic waters.Besides,G.lemaneiformis has been suggested to be a potential marine drug in assisted treatment for diseases and therefore,has variable applications and market values.In this paper,the response of seaweed G.lemaneiformis to environmental stress was studied in indoor seawater culture system.The impact of environmental factors including changes in temperature,salinity,light intensity,nitrogen,phosphorus, cadmium and dimethly phthalate on the growth of G.lemaneiformis were studied.In addition,the immunomodulatory and antitumour effects of the seaweed extraction were analysed using flow cytometry.The results were summarized as follows:(1) G.lemaneiformis showed high growth rate and normal ultrastructures of both chloroplast and mitochondrion at 22～25℃with 30‰salinity and with light intensity of 2000～2500 lx.Plasmolysis,disordered grana structure with loosen layer of thylakoid and irregular arrangement,vacuoles,blurry mitochondrion cista and inhibited growth of G.lemaneiformis were observed at 30℃with 22‰saltinity and with light intensity of 5000lx.(2) G.lemaneiformis showed increased growth rate with the concentration of N increased from 200μmol/L to 600μmol/L,as well as with the N/P concentrations increased from 50/3.13μmol/L to 400/25μmol/L.The growth rate decreased significantly with＞600μmol/L N or with＞400/25μnol/L N/P.The activity of nitrate reductase was inhibited at the above indicated concentrations.Increased number of swollen,irregularly aligned,ruptured and partly dissolved thylakoids have been observed in some cases.Also,increased volume of chloroplasts,significant accumulations of starch grains in chloroplasts and the reduced mitochondrion were observed.Given these results,a remediation critical point for the growth of G. lemaneiformis under high N or N/P concentrations was proposed.The critical concentration of N was 600μmol/L,and of N/P were 400/25μmol/L.The result also indicated that the seaweed possessed the capability of assimilating nitrogen selectively, and the sequencing of assimilating rate was NH₄⁺-N,NO₃^--N and NO₂^--N.(3) The growth of G lemaneiformis was influenced by changes in concentrations of pollutants and by the changes of exposure time in cadmium(Cd) or dimethly phthalate(DMP) treatment.The activities of enzyme of the seaweed were destroyed and contents of the soluble protein,chlorophyll a and phycoerythrin were decreased when the concentrations of Cd and DMP exceeded 10mg/L,0.2mg/L,respectively.At these concentrations,the ultrastructures of the seaweed cells were severely damaged including the occurring of marked plasmolysis,dissolved crista,disappearing of the chloroplast envelope,disturbed thylakoid and Cd precipitation near the cell wall, which resulted in remarkably inhibited growth of G.lemaneiformis.On the other hand, the Gracilaria has a certain resistance capability against Cd and DMP stress when the concentrations of Cd and DMP were lower than 3.0mg/L,0.1mg/L,respectively.(4) No statistical differences in CD45⁺ CD83⁺ / CD45⁺ and CD45⁺ CD80⁺ / CD45⁺ cell population were observed between BALB/c mice treated with different Gracilaria extraction and the control group(P>0.05).However,dose-dependent increasing in CD45⁺ TGF-β/ CD45⁺ cells was observed with the treatment of the seaweed extraction at different concentrations(R²=0.8145,P＜0.05).The optimized concentration of Gracilaria extraction was 2%.The research indicats the effective components of the seaweed have different immunomodulatory effects and merit further investigation.