| Desiccation tolerance is a strategy of survival strategy on their response to adverse environments,and the bryophyte was most plants species of organism that retain nutrient dehydration.But,in sensitive plants,their are dehydration that was retained in propagules.The process of dehydration tolerance of vegetative tissue is extremely complication while closely related to the surrounding environment,physiological structure and self-metabolism property.In the past experience,they may be center on an material component.As in recent year,the concept of omics has permeated into various research fields of biology,such as genomics,metabolomics,and proteomics,which have deepened the essential mechanism of our tolerance to plant dehydration.In this,as base on metabolomics,meanwhile combined with morphological and physiological changes,so we will established a model that could to comprehensive explains the dehydration tolerance of mosses.In this metabolomics model,to explain the relationship between dehydration tolerance and ecological adaptability,thereby to reveal the causes of the narrow distribution of the Dolichomitriopsis diversiformis and enhancing the theoretical understanding of the application of rocky desertification in the treatment of bryophyta species.The research results listed are as follows:1.in order to P.acutum as a comparison material,we are studied the water balance between rapid dehydration and rehydration.The results showed that the bryophytes were Both below 0.05 g H2O/g DW in D120,At this time,the water content of the D.diversiformis was only 0.7% comparison with control,and that of the P.acutum was 1.3%.so the capacity of water retention of P.acutum is greater than twice of D.diversiformis.2.The relative amounts of chlorophyll(SPAD)values of the leaves of P.acutum and D.diversiformis under normal conditions were 5.6 and 6.2,respectively,but on D120,their quickly dropped to lowest is 1.4 and 1.5,respectively.The SPAD values of the two species basically recovered on R60 were 5.5 and 5.5,respectively.Therefore,both of them belong to the homoiochlorophyllous resuscitation plants that dehydration degradation and rehydration resynthesis.in addition,the SPAD values of P.acutum upon D.diversiformis,overal,protective of PS?of P.acutum was better during dehydration/rehydration.3.In the study of photosynthetic fluorescence characteristics,the ETR-PAR(photoresponse curve)was decreased from 1327 ?mol·m-1·s-1 of normal group to 159 ?mol·m-1·s-1 of D30 during dehydration,and after D30 have not been light intensity response detected.Fv/Fm showed that the value was lowest than the control group when D120,0.3577.but R120,it was only 0.557,which failed to reach the control state.Y(II)also showed that the decrease from the 0.627 of control group to 0.0083 at the D120 level and 0.316 at the time of the R120 level,while failed to return to the control level,indicating that the photosynthetic system may be damaged irreversibly.4.the results analysis of xanthophylls cycle componen showed that the V /(A + Z)(violaxanthin /(Zeaxanthin + antheraxanthin)ratio represents response capacity of the plant.At the time of D60,V/A+Z dropped to the lowest value of 0.465.At D120,the tip of the D.diversiformis rose to 0.7086.as show that the peroxidation reaction beyond the limits and cannot withstand when abiotic stresses,and resulting in loss of Xanthophyll cycle capacity.5.In the degree of unsaturation,we was show that 17 kinds of fatty acids in the normal group,and 24 species detected at D120,which were mainly unsaturated fatty acids.However,the degree of unsaturation fatty acids of D.diversiformis was lower than the P.acutum,meanwhile both bryophytes were D120 is mainly some polyunsaturated fatty acids,such as linoleic acid,linolenic acid,etc.In adding to,the degree of unsaturation of D.diversiformis was rise at D120,while the membrane lipids were damaged.6.The ratio of unsaturated fatty acids in D.diversiformis of D200 was much lower than P.acutum,and In addition,the content of MDA in D120 was also higher than P.acutum,such has been proved that the cell membranes of D.diversiformis of the leaves are more susceptible to dehydration stress.7.Our results showed that there were significant metabolic changes in 84 components during of dehydration and rehydration after comparing the metabolomics and metabolomics databases.KEGG metabolic pathway analysis showed that the start of 50 types of metabolic pathways,and the amino acid,carbohydrate and fat metabolism is mainly.Finally,the analysis showed that the D.diversiformis dominant was mainly based on two metabolic pathways: energy dissipation and cell membrane protection.Based on the above findings,we believe that D.diversiformis is an intermediate between dehydration-tolerant and dehydration-sensitive plant.First of all,the redundant energy of D.diversiformis cannot be dissipated during dehydration,result in be destructed of xanthophyll cycle,and PSII is irreversibly damaged,while failure to repair in late.Second,the degree of unsaturation were change because of severe dehydration,It means that membrane lipids are damaged that severe affect protection of the dehydration process and repair of later stages.Finally,metabolomic profiling demonstrated that the metabolites component of D.diversiformis was singleness and these has not stable metabolic protection layer.The ability to retain water descend when undergo drought(dehydration),while the rapid loss of water,and the entry of water will be Irreversible damage to cell membranes and other intracellular tissues.Therefor,we are consider that the failure of the water's physiological ecosystem to form a synergistic and overall protection and repair system during the dehydration process is critical factors of its narrow distribution.In addition,desiccation tolerance critical factor is that dehydration process requires the initiated of a variety of metabolic pathways,a reversible photosynthetic system,and a reversible membrane lipid protective layer to ensure that the water physio-ecosystem is effective enough to form an effective protective mechanism,only If the stable restoration can survive the stress environment in the later period. |
PDF Full Text Request