| Soil salinization is recognized as a global problem and it is also a hot research topic in modern soil ecology.At present,it is known that about 20%of irrigated soils around the world are affected by salinity and show a deteriorating gradually year by year,which seriously threatens land utilization and crop yields.China's salinized land is widely distributed in large area with many types and it is concentrated distribution in North China Plain,Northeast Plain,Northwest China and coastal area.Salt and alkali damage has resulted in a large number of low-yielding fields and peasants poverty,so that large-scale use of soil resources difficult to reduce the comprehensive agricultural productivity,seriously affecting the development of agricultural production and peasants living standards.Saline-alkali stress reduces soil osmotic potential,unbalances ions,disrupts physiological processes,inhibits plant growth,reduces crop quality and yield,and in severe areas can even lead to plant death.Therefore,understanding the element content of plants under saline-alkali stress and analyzing the element distribution law of plants to salinity-alkalinity stress can improve plant's salt-tolerance ability,increase crop yield,alleviate the pressure of arable land in our country and promote the sustainable development of agriculture.In the domestic research,there are many researches on the physiological and biochemical reactions of plants under saline-alkali stress and exogenous regulation,but there were relatively few researches on differences of elements and metabolites of plants under saline-alkali stress.In this paper,taking the southeastern grassland of Hulunbeir as the research object,the community types of Hulunbeir grassland were investigated,and the element distribution characteristics of different parts of the main communities were studied.The distribution differences of mineral elements,primary metabolism and phenolic metabolism between Suaeda salsa and puccinellia tenuiflora under saline-alkali environment were further studied in order to apply the comprehensive analysis of ion group and metabolic group.The metabolism-ion regulation network of plants in saline-alkali soil was constructed in order to excavate the grass germplasm resources and functional metabolites with strong saline-alkali ecological adaptability,and to provide support for the development and utilization of grass germplasm resources.First of all,through the investigation of the community structure of the grassland in the southeast of Hulunbeir,it is found that there are five community types:(1)the xerophytic weed community is dominated by Leymus chinensis,and the species diversity of this community is relatively higher;(2)Achnatherum splendens community is dominated by Achnatherum splendens,Achnatherum splendens had the absolute predominance.(3)Suaeda salsa is dominated by severe saline-alkali community,and the diversity is very low.(4)Reed dominated the transition community from wet to xerophytic.(5)the main community is Iris.The abundance and diversity of species in saline-alkali land are very low,and there are no more than 10 species or even less than 3 species in the area.Suaeda salsa community and puccinellia tenuiflora community are pioneer communities growing in harsh saline-alkalinity environment.In this experiment,the main dominant species of Suaeda salsa community were Suaeda salsa,Chenopodium salsa and Polygonum sibiricum.The main dominant species of puccinellia tenuiflora community:puccinellia tenuiflora,alkali dandelion,Carex chinensis,salted plantain as the research object,comprehensive and comprehensive analysis of mineral elements in Suaeda salsa community and star grass community in various tissue parts(root,stem,The distribution in leaves).We found that the tolerance of Suaeda salsa community to saline-alkali was better than that of puccinellia tenuiflora community,and the absorption and accumulation of K,Ca,Na and Mg were also higher than that of star grass community.By comparing the contents of soil mineral elements between the two communities,it was found that there were significant differences in K,Na,Mg,Zn,Ni and B between puccinellia tenuiflora community and Suaeda salsa community,but there was no significant difference in other mineral elements.The results showed that the main elements causing the differences between the two communities were K,Na,Mg,Zn,Ni and B.Because of the remarkable saline-alkali resistance of Suaeda salsa and puccinellia tenuiflora,the main constructive species of puccinellia tenuiflora community and the main constructive species of Suaeda salsa community were studied.ICP-OES,GC-MS and LC-MS were used to determine and analyze the elements and metabolites in the roots,stems and leaves of Suaeda salsa and puccinellia tenuiflora,and the differences of element distribution and metabolite distribution between the two species were discussed.The following progress has been made in this study:(1)the contents and distribution of 11 elements in roots,stems and leaves of Suaeda salsa community and puccinellia tenuiflora community were comprehensively detected and analyzed by using the established ICP-OES method.Compared with Suaeda salsa,the habitat saline-alkali pressure of puccinellia tenuiflora plants will be less.The leaf,stem and root of puccinellia tenuiflora generally have lower Na enrichment coefficient and the lower Na transport coefficient,so the saline-alkali tolerance is significantly lower than that of Suaeda salsa.However,the enrichment coefficient of other mineral elements K,Ca,Mg,Zn,Cu,Fe and Mn was also significantly lower than that of Suaeda salsa,and the transport coefficient was also lower than that of Suaeda salsa.From the enrichment intensity of tissue parts,Suaeda salsa mineral elements K,Ca,Na:leaves>stems>roots;Mg:leaves>roots>stems.On the other hand,the enrichment degree of elements in each part of star grass was different from that of Suaeda salsa,Ca,Na,Mg:leaves>roots>stems,K:leaves>stems>roots.(2)the roots,stems and leaves of Suaeda salsa and puccinellia tenuiflora were analyzed by GC-MS non-targeting metabonomics technique.Using multivariate statistical analysis,the PLS-DA model was established,and the specificity among the tissues of each species was analyzed.As a result,it was concluded that Suaeda salsa and puccinellia tenuiflora could be clearly distinguished,and the credibility of the model was verified.According to the different importance of 225 compounds in projection(VIP,VIP>1)and P value(P<0.05),51 different metabolites were identified as the main factors to distinguish between tissues(VIP>1,p<0.05).They are divided into sugars,7 amino acids,5 alcohols,18 acids and 10 other compounds.The relative content of most metabolites in Suaeda salsa is higher than that in puccinellia tenuiflora,and these metabolites are mainly accumulated in the leaves and roots of Suaeda salsa.In addition,the relative content of these metabolites in puccinellia tenuiflora root has reached the lowest level in the root of Suaeda salsa.Among them,TCA members fumaric acid and citric acid mainly accumulated in the root,there was no significant difference between them,indicating that a large amount of energy was used to resist saline-alkali stress.(3)the roots,stems and leaves of Suaeda salsa and puccinellia tenuiflora were analyzed by LC-MS non-targeting metabonomics technique.The PLS-DA model was established,and the specificity among the tissues of each species was analyzed.As a result,the tissues of Suaeda salsa and puccinellia tenuiflora could be clearly distinguished,and the credibility of the model was verified.Finally,10 significantly different phenolic compounds were obtained.The abundance of these metabolites in Suaeda salsa and puccinellia tenuiflora are big differences.P-hydroxycinnamic acid,chlorogenic acid,luteolin and quercetin showed very significant accumulation in puccinellia tenuiflora,while p-hydroxybenzoic acid,eugenic acid,cinnamic acid,Gallic acid and protocatechuic acid showed very significant accumulation in Suaeda salsa.It is suggested that Suaeda salsa and puccinellia tenuiflora need to respond positively to salt stress by accumulating different phenolic compounds.In the enrichment analysis of metabolic pathway,we found that high levels of phenolic compounds,such as ferulic acid,genistein,L-phenylalanine,Gallic acid and rutin,were distributed in upper part of Suaeda salsa and puccinellia tenuiflora.However,higher levels of L-phenylalanine,Gallic acid and rutin were distributed in the shoot of Suaeda salsa compared with puccinellia tenuiflora.Therefore,Suaeda salsa and puccinellia tenuiflora are mainly transport more phenolic compounds such as L-phenylalanine,Gallic acid and rutin to the ground to scavenge free radicals,regulate ion homeostasis and alleviate salt stress.Suaeda salsa showed stronger salt tolerance.In the visual analysis of metabolic pathway,it was found that Suaeda salsa was mainly the accumulation of flavonol synthesis pathway,while the accumulation of main flavonoid synthesis pathway of puccinellia tenuiflora showed that the accumulation of phenolic compounds was multifunctional under stress.Suaeda salsa and puccinellia tenuiflora need to synthesize different ways to respond to stress and better adapt to the environment. |
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