Physiological Mechanism Research Of Bangia Fuscopurpurea And Bangia Atropurpurea In Response To Salinity Stress

Bangia has been widely applied in food,medicine,scientific research and other fields now base on its delicious tests and highly nutitional value.So the ecnomic value of Bangia is increasing.In this study,we used Bangia fuscopurpurea and Bangia atropurpurea as experimental materials to measure physiological and biochemical indexes under different stress conditions by chorophyll II fluorescence,photosynthetic oxygen evolution measurements,Non-invasive micro-test technology and LC-MS.And then,through analysis these indexes,we can deeply understand which antioxidant physical response during salinity stress of Bangia.It also provides a certain theoretical basis for some problems that arise in the development of Bangia cultivation.The experimental results are as follows:The F_v/F_mdeclined rapidly when B.fuscopurpurea in salinity lower than natural seawater,or B.atropurpurea in salinity higher than freshwater,and the decrease was positively related to the level of stress.The F_v/F_mof B.fuscopurpurea was significantly inhibited of S4 and S5.There was no significant difference among different hyposalinity stressed-groups of B.fuscopurpurea.The F_v/F_mof B.atropurpurea under hypersalinity stress was significantly lower than the control group since the first day,and recovered to the control level after 6-7d of hypersalinity treatment.Salinity stress had significantly effects on P_nof the both Bangia species.In general,R_ddecreased at the early stage and then rapidly recovered to the control level on the 1st day.There was no significant difference between the different lower salinity stress groups of B.fuscopurpurea after 3st day.And the P_nof hypersalinity continued of the B.atropurpurea was even reduced to a negative value.The change of R_din the early stage was consistent with F_v/F_m,firstly it decreased,and then quickly returned to the control level.R_dof the hyposalinity stressed B.fuscopurpurea groups was significantly lower than control.As the hypersalinity continued,R_dof the stressed B.atropurpurea increased and became significantly higher than control.After 3d,the F_v/F_mof B.fuscopurpurea decreased significantly under the treatment of 200-500?mol/L Na₃VO₄.F_v/F_mof B.atropurpurea was lower than the control during 1-6h under Na₃VO₄treatment,and then recovered to normal level in 12h treatment.Then,it decreased linearly with Na₃VO₄concentration increasing.With the treatment of salinities and Na₃VO₄simultaneously,there was no significantly different between control group and stress groups in the early stage.F_v/F_mof B.fuscopurpureawas dropped obviously in every salinity with 500?mol/L after 3 or 4d;But 200?mol/L of Na₃VO₄had a significantly inhibitory effect on S2 and S3.Na₃VO₄from 50 to 200?mol/L could promote the F_v/F_min S5,the higher concentration,the more obvious effect.At the end of the experiment,Na₃VO₄had significant inhibition on F_v/F_min S2-S4 groups.But in S1 group,only 500?mol/L decreased significantly.When B.fuscopurpurea in salinity lower than natural seawater or the B.atropurpurea in salinity higher than freshwater,P_ndecreased significantly with the treatment of 500?mol/L Na₃VO₄,it increased at 1st day,and then decreased significantly in each group,similar to the F_v/F_mresults.In early stage,P_nof B.fuscopurpurea of hyposalinity treatment was higher than control group.Groups of moderately lower salinity stress were gradually equivalent to the control group in late stage,only S5 group was significantly lower than the control.In late stage of B.atropurpurea experiment,P_nof S2 and S4 group even exceeded the control.R_dof all groups was at the same level in early stage?6h?;With the extension of stress time,R_dof both B.fuscopurpurea and B.atropurpurea increased as the stress becamestronger,which was more obvious in B.atropurpurea.The results revealed that Bangia responded quickly to salinity stress.The enhancement of R_dand regulation of plasma membrane-H⁺-ATPase may play an important role in Bangia response to salinity stress.Long-term salinity stress had irreversible harmful effects on the photosynthesis of Bangia.The results of H⁺and Na⁺ion current showed that:1)The control group,B.fuscopurpurea?S1?,H⁺and Na⁺were in the state of efflux,and B.atropurpurea?S5?H⁺inflow,Na⁺outflow.2)Under hyposalinity stresse of B.fuscopurpurea,H⁺and Na⁺efflux both decreased.And S3 group of H⁺flow has a greater degree of change,close to 0;Na⁺flow of S5 group changes more significantly,at 0 fluctuating up and down,S3 group decreased slightly compared with the control group.Under hypersalinity stress,H⁺inflow and Na⁺outflow of B.atropurpurea had a significant decrease in the S3 group,while S5 group has no significant change compared with the control.3)After the Na₃VO₄was added to the control group,the H⁺flow of B.fuscopurpurea changed from outer discharge to the inflow state,and the internal flow of H⁺of B.atropurpurea significantly decreased,both Na⁺efflux flow increased significantly.4)The salinity and Na₃VO₄stress at the same time,compared with the salinity stress alone,the H⁺outflow of B.fuscopurpurea was further inhibited and became inflow,while the Na⁺flow did not change significantly;the B.atropurpurea,H⁺inflow further suppressed,the S1 group even had a tendency to efflux.The Na⁺flow was slightly increased in S3 group,and efflux of the S1 group dropped significantly to around 0.From the above results,it can be seen that after salt stress,the H⁺flow activity was inhibited compared with the control,and the inhibition of H⁺flow was further enhanced by the addition of Na₃VO₄.Under different salinity conditions and Na₃VO₄,the B.fuscopurpurea Na⁺outflow performance is shown as S1 group>S3 group>S5 group?near 0?,that is,the higher the external environment[Na⁺],The greater the cell Na⁺effluent,it means that the cell membrane has always had a good barrier effect on the environmental Na⁺;B.atropurpurea under hypersalinity stress,the Na⁺effluent is S5 group?S1 group>S3 Group,after adding Na₃VO₄,It was S5 group>S3 group>S1 group?near 0 or slightly below 0?,that was,the higher the external environment[Na⁺],the less the amount of cellular Na⁺efflux in the S1 group even a small amount of influx appeared.This shown that the barrier effect of cell membrane on Na⁺was inhibited or other processes are involved.To sum up,after adding Na₃VO₄,the H⁺flow reversed in both types of Bangia,indicating that the regulation of plasma membrane H⁺-ATPase activity affected the H⁺flow.The two types of Bangia have reverse transport Na⁺under high salinity or Bangia has the ability to maintain intracellular Na⁺under low salinity,which provides a physiological basis for B.fuscopurpurea adapt to fresh water and B.atropurpurea adapt to seawater.In this process,there are other regulatory pathways besides plasma membrane H⁺-ATPase,which needs further study.The results of LC-MS showed that.In general,compared with the control group,the Biosynthesis of unsaturated fatty acids under salt stress was extremely significant,which may be related to the composition of the phospholipid bilayer on the cell membrane.When the Bangia under stress,the function of cell membrane was first mobilized.When B.atropurpurea under hypersalinity stress,Biosynthesis of unsaturated fatty acids and metabolic pathways were very significant difference pathways.But in B.fuscopurpurea,S3 group,Phenylalanine,tyrosine and tryptophan biosynthesis,Fatty acid biosynthesis and Oxidative phosphorylation were very significant differences in metabolic pathways;S5 group became Glutathione metabolism,Carbon fixation in photosynthetic organisms and Pyrimidine metabolism.Above,with different levels of salt stress,the difference of Biosynthesis of unsaturated fatty acids pathway was very significant of Bangia fuscopurpurea and B.atropurpurea.While compared with B.fuscopurpurea,the significantly differential metabolic pathways of B.atropurpurea were reduced,and the number of differential metabolites decreased under hypersalinity stress.These results indicated that the B.atropurpurea has strong adaptability to seawater.