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A Study On Physiological And Molecular Response Mechanisms Of Reaumiria Soongorica Seeds At Germination Stage Under Salt Stress

Posted on:2020-07-14Degree:MasterType:Thesis
Country:ChinaCandidate:X W LiuFull Text:PDF
GTID:2370330605966713Subject:Biochemistry and Molecular Biology
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Salt stress is one of the abiotic stresses that seriously affect the growth,development,yield and quality of agricultural and forestry plants.Salt tolerance of plants is diverse,plant species are different,and their salt tolerance mechanisms are also different.Compared with glycophytes,halophytes have evolved special salt tolerance response mechanism in the long-term interaction with saline-alkali soils.Reaumuria soongorica is a salt-secreting plant of Tamarix family.It has strong salt tolerance.It is a pioneer tree species for ecological restoration of saline-alkali land and an ideal material for analyzing salt tolerance mechanism of plants.Seed germination is a key stage in plant life history and a key link in difficult sites such as phytoremediation of saline and alkali.At present,the research on Reaumuria soongorica mostly focuses on the growth and physiological response of seedlings under salt stress,but seldom focuses on the mechanism of salt tolerance during the germination stage of Reaumuria soongorica seeds.In this study,Reaumuria soongorica seeds were used as experimental materials to explore the effects of different concentrations of Na Cl(0,50,100,200,300,400 m M)on the germination of Reaumuria soongorica seeds and their physiological responses to growth after germination.Salt tolerance during germination was evaluated to determine the optimum concentration of Na Cl for germination(L)and threshold concentration for germination(M).Based on this concentration,transcriptome sequencing was used to explore Reaumuria soongorica.In response to transcription level under stress,differentially expressed genes were screened and provide sequence information and gene resources for subsequent research.The main results are as follows:(1)Appropriate low salt concentration treatment promoted seed germination and growth after germination,while high salt concentration inhibited seed growth.Compared with the control,the germination rate of Reaumuria soongorica treated with 50 m M increased,and the root length and plant height increased significantly.With the increase of concentration,thegermination time of Reaumuria soongorica delayed,the germination rate decreased,the salt damage rate increased,and the contents of Malondialdehyde(MDA)and proline(Pro)in Reaumuria soongorica increased significantly,and the activities of peroxidase(POD)and superoxide dismutase(SOD)increased in varying degrees,but root length and plant height decreased significantly.When the salt concentration increased to 400 m M,it could not germinate,but still remained the germination vigor.Using the relative germination rate and the plant length decreased to 50% of those in the control as a standard,the germination salt tolerance threshold was 273 m M and the optimum salt concentration was 45.78 m M.and the growth salt tolerance threshold was 388.19 mmol/L and the optimum one was 50.59 m M respectively.(2)Nine samples of Reaumuria soongorica seed under germination stage were sequenced by transcriptome,and 72.54 Gbp of clean reads were obtained.292881 transcripts and 238532 unigenes were obtained by splicing.Among them,134684 unigenes were successfully annotated in at least one database,accounting for 56.46% of the total unigenes.Only 16054 unigenes were successfully annotated in all databases.Among these successful annotated databases,the NR database has the highest annotation success rate,with 115757(48.52%)unigenes.Successful annotated species are mainly Beta vulgaris,Vitis vinifera,Theobroma cacacao,Nelumbo nucifera,Jatropha curcas and so on.210,2273 and 2888 differentially expressed genes(DEGs)were screened out in Lvs C,Mvs C,Mvs L,respectively,of which 116 were up-regulated and 94 were down-regulated in Lvs C,1781 were up-regulated and 492 were down-regulated in Mvs C,2165 were up-regulated and 723 were down-regulated in Mvs L.In KEGG the up-regulated genes were mainly concentrated in ribosome,carbon metabolism,cytochrome P450 metabolism,glutathione metabolism and other pathways;down-regulated genes were mainly concentrated in sucrose and starch metabolism,endoplasmic reticulum protein processing and other processes.In conclusion,the optimum and threshold concentration of seed germination stage were determined through experiments.By analyzing the physiological response characteristics of seeds during germination under salt stress and combining with transcriptome data ofgermination stage under salt stress,the results showed that Reaumuria soongorica seeds could enhance their salt tolerance and germination rate by enhancing their respiration and antioxidant capacity,thus enhancing their natural regeneration ability under salt stress.This study revealed the physiological regulation characteristics of red sand seed germination under salt rib stress,and provided basic data and data support for further study of salt tolerance mechanism of Reaumuria soongorica.
Keywords/Search Tags:Reaumuria soongorica, seed germination, salt tolerance evaluation, transcriptome analysis
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