Cytochemical localization of ATPase and sub-cellular variation in mesophyll cell of Cyclocarya paliurus seedlings under iso-osmotic stress and calcium regulation

The ultrastructural distribution and active location of ATPase and the ultrastructural variations were investigated in mesophyll cells of Cyclocarya paliurus seedlings after iso-osmotic salt/water treatments in combination with calcium regulation. C. paliurus seed- lings were treated with five groups （control, 85 mM NaCl, 85 mM NaCl＋ 12 mM Ca（NO3）2, PEG iso-osmotic to 85 mM NaCl and PEG iso-osmotic to 85 mM NaCl＋12 mM Ca（NO））2） in a hydroponic system in a phytotron. Results show that under normal growth conditions the ATPase activity was low and the enzyme was primarily located on the nucleus. After 12 days of iso-osmotic salt/water treatments, ATPase activity on the tonoptast increased. Osmiophilic globules for iso-osmotic water treatment were greater than that for iso-osmotie salt treatments. The ATPase activity increased and was mostly transferred onto the nucleus for calcium regulation treatment under iso- osmotic salt/water stresses, and the osmiophilic globules significantly decreased under iso-osmotic water stress with calcium regulation. The ATPase located on the nucleus indicated that the degree of salt/drought damage that seedlings suffered was slighter, while the amount of the enzyme located on the tonoplast showed that the degree of salt/drought damage there was more serious. After 4 and 20 days of iso- osmotic treatments, the injury suffered by the leaf ultrastructures of C. paliurus seedlings for iso-osmotic treatment with calcium regula- tion was lower than those without calcium regulation, especially for the iso-osmotic water treatments. Preliminary analysis suggests that the iniury suffered by C. paliurus seedlings was lower for iso-osmotic salt treatments than for iso-osmotic water treatments, while the effect of calcium regulation under iso-osmotic water stress was greater than that of the iso-osmotic salt stress.

Synergistic effects of carbon cycle metabolism and photosynthesis in Chinese cabbage under salt stress

Chinese cabbage(Brassica rapa ssp. pekinensis) has a long cultivation history and is one of the vegetable crops with the largest cultivation area in China. However, salt stress severely damages photosynthesis and hormone metabolism, nutritional balances, and results in ion toxicity in plants. To better understand the mechanisms of salt-induced growth inhibition in Chinese cabbage, RNA-seq and physiological index determination were conducted to explore the impacts of salt stress on carbon cycle metabolism and photosynthesis in Chinese cabbage. Here, we found that the number of thylakoids and grana lamellae and the content of starch granules and chlorophyll in the leaves of Chinese cabbage under salt stress showed a time-dependent response, first increasing and then decreasing. Chinese cabbage increased the transcript levels of genes related to the photosynthetic apparatus and carbon metabolism under salt stress, probably in an attempt to alleviate damage to the photosynthetic system and enhance CO_(2) fixation and energy metabolism. The transcription of genes related to starch and sucrose synthesis and degradation were also enhanced;this might have been an attempt to maintain intracellular osmotic pressure by increasing soluble sugar concentrations. Soluble sugars could also be used as potential reactive oxygen species(ROS) scavengers, in concert with peroxidase(POD)enzymes, to eliminate ROS that accumulate during metabolic processes. Our study characterizes the synergistic response network of carbon metabolism and photosynthesis under salt stress.

Genome-Wide Exploration of the Grape GLR Gene Family and Differential Responses of VvGLR3.1 and VvGLR3.2 to Low Temperature and Salt Stress

Grapes,one of the oldest tree species globally,are rich in vitamins.However,environmental conditions such as low temperature and soil salinization significantly affect grape yield and quality.The glutamate receptor(GLR)family,comprising highly conserved ligand-gated ion channels,regulates plant growth and development in response to stress.In this study,11 members of the VvGLR gene family in grapes were identified using whole-genome sequence analysis.Bioinformatic methods were employed to analyze the basic physical and chemical properties,phylogenetic trees,conserved domains,motifs,expression patterns,and evolutionary relationships.Phylogenetic and collinear analyses revealed that the VvGLRs were divided into three subgroups,showing the high conservation of the grape GLR family.These members exhibited 2 glutamate receptor binding regions(GABAb and GluR)and 3-4 transmembrane regions(M1,M2,M3,and M4).Real-time quantitative PCR analysis demonstrated the sensitivity of all VvGLRs to low temperature and salt stress.Subsequent localization studies in Nicotiana tabacum verified that VvGLR3.1 and VvGLR3.2 proteins were located on the cell membrane and cell nucleus.Additionally,yeast transformation experiments confirmed the functionality of VvGLR3.1 and VvGLR3.2 in response to low temperature and salt stress.Thesefindings highlight the significant role of the GLR family,a highly conserved group of ion channels,in enhancing grape stress resistance.This study offers new insights into the grape GLR gene family,providing fundamental knowledge for further functional analysis and breeding of stress-resistant grapevines.

Tomato Key Sucrose Metabolizing Enzyme Activities and Gene Expression Under NaCl and PEG Iso-Osmotic Stresses

Changes in sucrose metabolism in response to salt （NaC1） and water （polyethylene glycol, PEG6000） iso-osmotic stresses were measured in tomato cultivar Liaoyuan Duoli （Solanum lycopersicum L.） and the objective was to provide a new evidence for the relationship between salt and osmotic stresses. The carbohydrate contents, as well as sucrose metabolizing enzymes activities and transcript levels were determined. The results indicated that soluble sugar and hexoses accumulated to higher levels and the contents of sucrose and starch were lower in mature fruit under the two stress treatments. Salt and water stresses can enhance the invertase and sucrose synthase activities of tomato fruit in a long period of time （45-60 days after anthesis）, and elevate the expression of soluble acid invertase mRNA. It showed that two different stresses could also regulate the soluble acid invertase activity by controlling its gene expression. The activity of sucrose synthase was linked to the changes in soluble sugar levels but not with transcript levels. The effects of salt and water stress treatments on sucrose phosphate synthase activities were weak.

Nitrogen application regulates antioxidant capacity and flavonoid metabolism,especially quercetin,in grape seedlings under salt stress

Salt stress is a typical abiotic stress in plants that causes slow growth,stunting,and reduced yield and fruit quality.Fertilization is necessary to ensure proper crop growth.However,the effect of fertilization on salt tolerance in grapevine is unclear.In this study,we investigated the effect of nitrogen fertilizer(0.01 and 0.1 mol L^(-1)NH_(4)NO_(3))application on the salt(200 mmol L^(-1)NaCl)tolerance of grapevine based on physiological indices,and transcriptomic and metabolomic analyses.The results revealed that 0.01 mol L^(-1)NH_(4)NO_(3) supplementation significantly reduced the accumulation of superoxide anion(O_(2)^(-)·),enhanced the activities of superoxide dismutase(SOD)and peroxidase(POD),and improved the levels of ascorbic acid(AsA)and glutathione(GSH)in grape leaves compared to salt treatment alone.Specifically,joint transcriptome and metabolome analyses showed that the differentially expressed genes(DEGs)and differentially accumulated metabolites(DAMs)were significantly enriched in the flavonoid biosynthesis pathway(ko00941)and the flavone and flavonol biosynthesis pathway(ko00944).In particular,the relative content of quercetin(C00389)was markedly regulated by salt and nitrogen.Further analysis revealed that exogenous foliar application of quercetin improved the SOD and POD activities,increased the AsA and GSH contents,and reduced the H_(2)O_(2) and O_(2)^(-)·contents.Meanwhile,10 hub DEGs,which had high Pearson correlations(R^(2)>0.9)with quercetin,were repressed by nitrogen.In conclusion,all the results indicated that moderate nitrogen and quercetin application under salt stress enhanced the antioxidant system defense response,thus providing a new perspective for improving salt tolerance in grapes.

Mixed-Oligosaccharides Promote Seedling Growth of Direct-Seeded Rice under Salt and Alkaline Stress

Rice direct seeding technology is an appealing alternative to traditional transplanting because it conserves labor and irrigation resources.Nevertheless,there are two main issues,salt stress and alkaline stress,which contribute to poor emergence and seedling growth,thereby preventing the widespread adoption and application of this technique in the Ningxia Region of China.Therefore,to determine whether germination can be promoted by mixed-oligosaccharide(KP)priming(in which seeds are soaked in a KP solution before sowing)under salt and alkaline stress,a proteomics study was performed.KP-priming significantly mitigated abiotic stress,such as salt and alkaline stress,by inhibiting root elongation,ultimately improving seedling establishment.By comparing the proteomics analyses,we found that energy metabolic pathway was a vital factor in KP-priming,which explains the alleviation of salt and alkaline stress.Key proteins involved in starch mobilization,pyruvate mobilization,and ATP synthesis,were up-regulated by KP-priming,significantly blocking salt and alkaline-triggered starch accumulation while enhancing pyruvate metabolism.KP-priming also up-regulated ATP synthase to improve energy efficiency,thereby improving ATP production.In addition,it enhanced antioxidant enzymatic activities and reduced the accumulation of reactive oxygen species.All of these factors contributed to a better understanding of the energy regulatory pathway enhanced by KP-priming,which mediated the promotion of growth under salt and alkaline conditions.Thus,this study demonstrated that KP-priming can improve rice seed germination under salt and alkaline stress by altering energy metabolism.

Melatonin Alleviates Abscisic Acid Deficiency Inhibition on Photosynthesis and Antioxidant Systems in Rice under Salt Stress

Melatonin and abscisic acid,as major plant hormones,play important roles in the physiological and biochemical activities of crops,but the interaction between the two under salt stress is not yet clear.This study investigated the endogenous levels of melatonin and abscisic acid in rice by using exogenous melatonin,abscisic acid,and their synthetic inhibitors,and examined their interactions under salt stress.The research results indicate that melatonin and abscisic acid can improve rice salt tolerance.Melatonin alleviated the salt sensitivity caused by abscisic acid deficiency,increased antioxidant enzyme activity and antioxidant content in rice treated with abscisic acid synth-esis inhibitors,and reduced total reactive oxygen species content and thiobarbituric acid reactive substance accu-mulation.Melatonin also increased the activity of key photosynthetic enzymes and the content of photosynthetic pigments,maintaining the parameters of photosynthetic gas exchange and chlorophyllfluorescence.In summary,melatonin alleviated the effects of abscisic acid deficiency on photosynthesis and antioxidant systems in rice and improved salt tolerance.This study is beneficial for expanding the understanding of melatonin regulation of crop salt tolerance.

EuSHT Acts as a Hub Gene Involved in the Biosynthesis of 6-Hydroxyluteolin and Quercetin Induced by Salt Stress in Eucommia ulmoides

Salt stress inhibits plant growth and affects the biosynthesis of its secondary metabolites.Flavonoids are natural compounds that possess many important biological activities,playing a significant role in the medicinal activity of Eucommia ulmoides(E.ulmoides).To investigate the mechanism by which salt stress affects the biosynthesis of flavonoids in E.ulmoides,a comprehensive analysis of metabolomics and transcriptomics was conducted.The results indicated that salt stress led to the wilting and darkening of E.ulmoides leaves,accompanied by a decrease in chlorophyll levels,and significantly induced malondialdehyde(MDA)and relative electrical conductivity.During salt stress,most metabolites in the flavonoid biosynthesis pathway of E.ulmoides were upregulated,indicating that flavonoid biosynthesis is likely the main induced pathway under salt stress.Among them,secondary metabolites such as 6-Hydroxyluteolin and Quercetin are likely key metabolites induced by salt stress.The correlation analysis of transcriptomics and metabolomics revealed that EuSHT is a hub gene induced by salt stress,promoting the production of flavonoids such as 6-Hydroxyluteolin.The co-expression network showed a strong positive correlation between EuSHT and the biosynthesis of 6-Hydroxyluteolin and Quercetin,while it exhibited a negative correlation with Catechin biosynthesis.The branches leading to Luteolin and Dihydroquercetin are likely the main pathways for flavonoid compound biosynthesis in the plant stress response during salt stress.The results of this study provided a preliminary mechanism of secondary metabolites such as flavonoids in the medicinal plant E.ulmoides induced by salt stress and provided new theoretical support for discussing the mechanism of plant stress response.It also provided useful information for subsequent exploration of resistance genes in E.ulmoides.

Different Approaches to Reduce Salinity in Salt-Affected Soils and Enhancing Salt Stress Tolerance in Plants

Salt stress is one of the most harmful environmental stresses in recent times and represents a significant threat to food security. Soil salinization is caused by spontaneous natural processes of mineral dissolution and human activities such as inappropriate irrigation practices. Natural geological progressions like weathering of rocks, arid climate, and higher evaporation, as well as anthropogenic activities, including the use of brackish water for irrigation, and poor tillage operations, are the foremost causes of soil salinization. Typical characteristics of saline soils are salt stress, high pH, and lack of organic carbon, as well as low availability of nutrients. Disruption of precipitation patterns as well as high average annual temperatures due to climate change additionally negatively affects the process of soil salinization. Productivity and ability to support crop growth are reduced on saline soil. Salinity-induced stress reduces plant growth by modulating the antioxidative system and nutrient orchestration. The aim of this work is to show that the mentioned problems can be alleviated in several ways such as the addition of biochar, exogenous application of several elicitors, seed priming, etc. Research has shown that the addition of biochar can significantly improve the recovery of saline soil. The addition of biochar has no significant effect on soil pH, while the cation exchange capacity of the soil increased by 17%, and the electrical conductivity of the saturated paste extract decreased by 13.2% (depends on the initial salinity and the type of biochar raw material). Moreover, biochar enriched with silicon increases the resistance of bananas to salt stress. In addition, exogenous application of several elicitors helps plants to alleviate stress by inducing stress-related physicochemical and molecular changes (selenium, sulfur, silicon, salicylic acid). Finally, seed priming showed positive effects on metabolomics, proteomics and growth of plants subjected to abiotic stress. Priming usually involves immersing the seed in a solution for a period of time to induce physiological and metabolic progression prior to germination.

Genome-Wide Identification of ALDH Gene Family under Salt and Drought Stress in Phaseolus vulgaris

Background:Aldehyde dehydrogenase(ALDH)genes constitute an important family of supergenes that play key roles in synthesizing various biomolecules and maintaining cellular homeostasis by catalyzing the oxidation of aldehyde products.With climate change increasing the exposure of plants to abiotic stresses such as salt and drought,ALDH genes have been identified as important contributors to stress tolerance.In particular,they help to reduce stress-induced lipid peroxidation.Objectives:This study aims to identify and characterize members of the ALDH supergene family in Phaseolus vulgaris through a genome-wide bioinformatic analysis and investigate their role in response to abiotic stressors such as drought and salt stress.Methods:Genome-wide identification of 26 ALDH genes in P.vulgaris was performed using bioinformatics tools.The identified ALDH proteins were ana-lyzed for molecular weight,amino acid number,and exon number.Phylogenetic analysis was performed to clas-sify P.vulgaris,Arabidopsis thaliana,and Glycine max ALDH proteins into different groups.Strong links between these genes and functions related to growth,development,stress responses,and hormone signaling were identified by cis-element analysis in promoter regions.In silico expression,analysis was performed to assess gene expression levels in different plant tissues.Results:RT-qPCR results showed that the expression of ALDH genes was signif-icantly altered under drought and salt stress in beans.This study provides a comprehensive characterization of the ALDH supergene family in P.vulgaris,highlighting their potential role in abiotic stress tolerance.Conclusion:Thesefindings provide a basis for future research on the functional roles of ALDH genes in enhancing plant resis-tance to environmental stressors.

Study on Salinity Tolerance of Tomatoes during Seed Germination under Different Salt Stress Conditions

[Objective] The aim of this study was to provide the theoretical basis for screening and utilizing salt-tolerant tomato varieties as well as for cultivating salt-resistance.[Method] Salinity tolerance of tomato during seed germination under simple salt sodium chloride and double salt calcium nitrate or sodium chloride stress were studied by Petri dish culturing.[Result] As the two kinds salt concentration increased,the germination regularity,the germination rate,the germination index and the growing vigor index of tomato seedlings decreased,but the germination losing rate increased.When salt concentration was from 0.2% to 0.4%,there was little difference among all indexes under two kinds of salt stress.However,when salt concentration was from 0.6% to 1.0%,the difference among all indexes under two kinds of salt stress was significant.[Conclusion] Salinity tolerance of tomato seeds under double salt calcium nitrate or sodium chloride stress was higher than that under simple salt sodium chloride stress.

Effects of Salt Stress on Fatty Acid Composition of Thylakoid Membrane of Two Rice Cultivars Differing in Salt Tolerance

[Objective] The aim of the study is to understand the changes of fatty acid composition of rice thylakoid membrane under salt stress.[Method] Under salt stress of different concentrations of NaCl,rice seedlings of Pokkali and Peta with six leaves and one central leaf were used as experimental materials to extract the fatty acid from their thylakoid membranes,and gas chromatograph(1890)was used to analyze fatty acid composition.[Result] Fatty acid component 14∶0,18∶0,16∶1(3t),18∶1 in both the two experimental materials showed little variations in the first four days of salt stress,whereafter they increased slightly;while the fatty acid component 16∶0 and level of saturation of fatty acid(LSFA)showed the similar variation trend in the first four days of treatment compared to those of the fatty acid components mentioned above,whereafter they rose in Pokkali and presented an opposite variation trend in Peta;fatty acid component 18∶3 and level of unsaturation of fatty acid(LUFA)reduced all the time under stress condition,and the reducing amplitude in 100 mmol/L NaCl treatment group was smaller than that of 100 mmol/L NaCl treatment group,and in Pokkali was smaller than that in Peta under specific conditions.Meanwhile,level of saturation of fatty acid in both experimental materials increased,and the rising amplitude in Peta was smaller than that of Pokkali.[Conclusion] With regard to LUFA,Pokkali is endowed with more salt tolerance than Peta.

Ornithine Pathway in Proline Biosynthesis Activated by Salt Stress in Barley Seedlings

C-14-glutamate and C-14-arginine were spreaded on leaves of six-day old barley (Hordeum vulgare L.) seedlings that were treated with NaCl 200 mmol/L. The result showed that the pathway of arginine-->ornithine-->proline existed in the six-day old barley seedlings and was provoked remarkably by NaCl treatment. After seven days, proline accumulation contributed via the arginine-->ornithine-->proline pathway was 1.0 - 1.5 folds of that via the glutamate-->proline pathway. The activation of arginine-->ornithine-->proline pathway by salt stress in the salt-tolerant cultivar 'Jian 4' was 1.7 - 2.0 folds of that in the salt-sensitive cultivar 'KP 7', which suggested that the activation of arginine-->ornithine-->proline pathway in barley seedlings played an important role in improving salt tolerance of plants.

Cloning and Differential Gene Expression of Two Catalases in Suaeda salsa in Response to Salt Stress

Two different cDNA clones (Sscat1 and Sscat2) encoding catalase, the primary important H2O2-scavenging enzyme, were isolated from a AZap-cDNA library constructed from a 400 mmol/L NaCl-treated library of Suaeda salsa ( L.) Pall aerial tissue. Sscat1 (1.7 kb) contains a full open reading frame of 492 amino acids and Sscat2 (1.1 kb) is a partial clone. BLAST analysis indicates that the two clones share 71.9% identity in nucleotide sequence and 75% identity in deduced amino acid sequence within the last 287 amino acid residues of Sscat1. Southern blotting analysis showed that Sscat1 is multicopy in S. salsa genome, while Sscat2 is a single copy gene. Northern blotting analysis showed a rapid increase in the steady-level of both genes in roots after 48 It salt treatment, but only Sscat1 was induced in salinity treated leaves. Time-course analysis carried out in leaves confirmed that Sscat1 was induced by salt stress, in contrast to Sscat2. These implied that the expression of Sscat1 and Sscat2 genes are differentially regulated in S. salsa. The activity of total catalase is dramatically increased in response to salt stress.

Mechanism of the Effect of Polyamines on the Activity of Tonoplasts of Barley Roots Under Salt Stress

The seeds of barley Hordeum vulgare L. cv. Jian 4) were soaked with 0.1 mmol/L putrescine (Put) and 0.5 mmol/L spermidine (Spd), and then the seedlings were treated with 200 mmol/L NaCl. The growth rate (GR), dry matter accumulation, distribution of ions, the amount of polyamines (PAs) bound to tonoplast proteins as well as lipid composition and the activity of tonoplast vesicles isolated from roots were investigated. The results showed that soaking with Put or Spd could retard salt injury, promote GR and dry matter accumulation, and increase K+/Na+ in the roots. Compared with NaCl_treated plants, phospholipid content in root tonoplast rose by soaking with Put and Spd, while the level of galactose in lipids was decreased. Moreover, the ratio in noncovalently conjugated PA contents of (Spd+PAx (an unknown PA)) to (Put+Dap (diaminopropane)), and the total contents of covalently and noncovalently conjugated PAs were all increased. Statistical analysis indicated that the ratio of (Spd+PAx) to (Put+Dap) was significantly and positively correlated with the activities of membrane associated enzymes H+_ATPase and H+_PPase.

Effects of Photoinhibition and Its Recovery on Photosynthetic Functions of Winter Wheat Under Salt Stress

Effects of photoinhibition and its recovery on photosynthetic functions of winter wheat (Triticum aestivum L.) under salt stress were studied. The results showed that several parameters associated with PSⅡ functions, e.g. Fv/Fo?Fv/Fm and qP were not influenced by lower salt concentration (200 mmol/L NaCl) while CO 2 assimilation rate decreased significantly. When exposed to higher salt concentration (400 mmol/L NaCl), PSⅡ functions were significantly inhibited which led to the decrease of carbon assimilation. These results suggest that different concentrations of salt stress affected photosynthesis by different modes. Salt stress made photosynthesis more sensitive to strong light and led to more serious photoinhibition. Under lower concentration of salt stress, the Q B-non-reductive PSⅡ reaction centers formed at the beginning of photoinhibition could be effectively used to compose active PSⅡ reaction center (RC) and repair the reversible inactivated PSⅡ RC. Under higher concentration of salt stress, PSⅡ reaction centers were seriously damaged during photoinhibition, the Q B-non-reductive PSⅡ RC could only be partly effective at the early time of photoinhibition, thus led to the accumulation of Q B-non-reductive PSⅡ RC in the course of restoration under dim light.

Changes in Physiological Properties and Respiratory Pathway of the New Lines of Wheat Introduced Exogenous DNA Under Salt Stress

New lines of wheat ( Triticum aestivum L.) was obtained by introducing the DNA of sorghum (Sorghum vulgare Pers.) into wheat cultivar 'Longchun 13'. The changes of respiratory pathway, contents of protein, Na+ and K+ in the leaves and roots of the new lines of wheat under salt stress were determined and compared with the control cultivar, 'Longchun 13'. The decrease of the content of K+ was observed with the increase of NaCl concentrations, but the decrease was more in the control than that in the new lines, and more in roots than in leaves. Content of proline and Na+ in both two wheats lines increased greatly, but the former increased more significantly in the new lines and the latter more significantly in control both in leaves and roots. The operation of the cyanide-resistant pathway of respiration was enhanced at different degrees after salt stress and it increased much more in roots and leaves of the control plant than that in the new lines, but the cytochrome pathway of electron transport was still the main one consistently. The possible significance of these changes was discussed.

Effect of Exogenous GSH on Growth of Barley Seedlings under Salt Stress

The growth of barley (Hordeum vulgare L.) seedling is inhibited by 300 mmol/L NaCl. When 20 mg/L GSH is present in the hydroponic culture solution with NaCl, root length, root and shoot dry weigh, chlorophyll as well as K+ contents are increased, Na+ content is decreased. At the same time the activities of H+-ATPase and H+-PPase associated with tonoplast vesicles isolated from leaves are stimulated, and electrolytic leakage are diminished by exogenous GSH.

Protective Effects of Glycinebetaine on Brassica chinensis Under Salt Stress

Brassica chinensis L. were foliarly applied with glycinebetaine (GB), as this species is unable to synthesis GB and sensitive to osmotic stress such as salt. The exogenous GB was easily absorbed and transported by the leaf of B. chinensis . Its application (0-20 mmol/L) enhanced the plant tolerance to salt stress. The treatment of 15 mmol/L GB significantly decreased the Na + accumulation in leaf and root under NaCl stress. This difference in accumulating Na + and K + is caused by higher selectivity of root absorption. Furthermore, GB increased H +_ATPase activity of root plasma membrane evidently. This result strongly suggested that in root the decreased Na + accumulation was caused by the GB accumulation that enhanced the extrusion of Na + from the cell in some way through plasma membrane transporter, e.g. Na +/H + antiport driven by H +_ATPase. The GB application was also found to stabilize the plasma membrane, to decrease the loss of chlorophyll, and to stimulate the osmosis induced proline response under salt stress.

Effects of Polyamines on Plants under Salt Stress

Salt stress is one of the worldwide abiotic stresses resulting in growth re- duction, chlorosis, wilting, and plant death. These exhibitions might result from men- tal toxicity and osmotic stress induced by salt. The two aspects of stress would af- fect vital metabolic pathways, reactive oxygen species scavenging system, lipid per- oxidation and photosynthetic apparatus. Thus, exploring ways to improve crop pro- ductivity or alleviate harmful effects under salt is one of the major areas of concern. Polyamines are aliphatic nitrogen organic cations which are implicated in a wide range of plant physiological processes such as morphogenesis, flower differentiation and initiation, they also play a role in biotic or abiotic stress responses. At the physiological level, polyamines modify the activities of many enzymes included in salt stress response and can bond to photosynthetic apparatus, thus changing the photosynthetic efficiency. At molecular level, polyamines can modify expressions of the polyamine-related genes directly or indirectly. Significant researches had been done to understand the effects of polyamines on plant salt resistance, but several questions still need to be answered. The present review is focused specifically on the effects of polyamines on physiological and molecular changes in plants under salt stress.