| Suaeda salsa(L.)Pall It is a common halophyte and often grows in coastal,salt marsh,desert and other saline-alkali land areas.It is the pioneer species and important ecological restoration species of tidal flat.In this paper,the effects of water and salt conditions on the ecological restoration species Suaeda salina were explored from the two environmental factors of salinity and flooding.The effects of water and salt conditions on Suaeda salsa and its response mechanism to the environment were comprehensively analyzed from three levels of macro phenotype,physiology and biochemistry,and transcriptome regulation.This paper first carried out species identification and genetic diversity analysis of Suaeda plants along the coast of Shanghai.At present,there are relatively few local surveys of Suaeda plants in Shanghai.This paper provides some data support for the protection and utilization of plant resources in Shanghai.The sampling points cover three administrative districts along the coast of Shanghai(Chongming District,Pudong New District and Fengxian District),and a total of 55 samples of Suaeda plants were collected.First,preliminary morphological identification was carried out according to the description in Flora of China.Then the ITS and mat K sequences were verified by using DNA barcode technology at the molecular biological level.The identification results of the two confirmed each other.The samples in this study included two species:Suaeda salsa(L.)Pall.and Suaeda glauca(Bunge)Bunge.The phylogenetic tree constructed based on ITS and mat K sequences supports the sample to be divided into two main branches,and the two tree building methods have high support rates.Therefore,both morphological and molecular biological methods can better identify and distinguish these two species.The degree of differentiation between Suaeda salsa populations in Shanghai is generally low.The gene exchange between populations is non-random and limited.The gene flow plays a homogenization role and dominates the genetic structure.This paper suggests using ITS+mat K or mat K sequence to identify Suaeda,construct NJ phylogenetic tree and analyze its genetic structure.Determination of germination rate and seedling growth index of type II seeds under different salinity and water flooding.It was found that the optimum ratio of water and salt for the germination of brown seeds was(salinity 0,water flooding 4 h),and the optimum ratio of water and salt for the germination of black seeds was(salinity 5,water flooding less than 4 h).Brown seeds of Suaeda salsa in saline soil are greatly affected by salinity,while black seeds are greatly affected by water flooding.In the experiment,it was also found that brown seeds tend to sink when absorbing water and gain weight,while black seeds tend to float upward.In the natural environment,brown seeds are more likely to be planted near their parents,while black seeds are more likely to migrate with tide and surface runoff,thus forming differences in geographical space.Through the determination of chlorophyll content and green fluorescence parameters of seedlings under different salinity and waterlogging treatments,it was found that salinity 10 and 30 promoted the synthesis of Chl a and Chl b in Suaeda salsa leaves,but salinity changes did not change the chlorophyll composition of plants.Chlorophyll has little correlation with the duration of flooding,and its regularity is not strong.It is speculated that Suaeda salsa has the ability to resist adversity,and the salinity and F_v/F_m after flooding treatment can not reach the initial level.It is speculated that the photosynthesis of Suaeda salina is affected by complex environmental factors,and the optimal range of other environmental factors cannot be fully simulated after controlling the variables.Moreover,the experiment period of this study is long,which may be that Suaeda salina has adapted to water and salt factors by regulating plant hormones and photosynthetic enzymes.The determination of SOD,total protein and MDA of seedlings under different salinity and flooding treatments showed that the T-SOD of Suaeda salsa seedlings reached saturation under salinity 20.Under waterlogging treatment,it may be due to shallow pot planting,and low waterlogging time may cause plant drought,resulting in high T-SOD content.The effect of long-term submergence on T-SOD was not significant.TPC plays a regulatory role in plant cells.When salinity stress occurs,the content of TPC increases,compensates for the osmotic potential caused by external salinity,and reduces salt damage to a lower level.From the content of T-SOD and MAD,we can see that the regulatory effect is good.MDA is the final product of plant cell membrane lipid peroxidation,which can reflect the damage of plant biofilm system.The transcriptome sequencing analysis of seedlings under different salinity and flooding treatments showed that the genes encoding sesquiterpene and triterpene biosynthesis of Suaeda salsa seedlings were up-regulated under high salinity conditions,and the mechanism of salinity stress was similar to drought stress,resulting in the physiological drought of plants.The significant up-regulation of genes related to the biosynthesis of cutin,cork and wax,the synthesis of these substances is accompanied by the construction of defense plant tissue,indicating that Suaeda salina has produced an adaptive mechanism to salinity stress.The genes involved in the regulation of flavonoids biosynthesis and beet red pigment biosynthesis have also been enriched,which plays a certain role in plant stress resistance.When flooded for 14 hours,the enrichment of N-glycosylation pathway was the highest,and the biosynthesis of N-sugar was also related to the stress response of plants.MYB transcription factors belong to the super transcription factor family.They are mainly involved in the regulation of plant reproductive development,stress resistance and adaptability,and play an important role in promoting flower formation.Exploring the regulation mode of Suaeda salsa MYB will help to explain the mechanism of adaptation under salinity and flooding stress more deeply. |
