Salt Stress Effect on the Growth and Physiological Characteristics of Three New Varieties of Lagerstroemia indica

The effects of different concentrations of NaCI （0, 0.10%, 0.25%, 0.40%, 0.55%, 0.70%） on the growth and physiological characteristics of three new varieties of Lagerstroemia indica were studied by pot experiment in the plastic greenhouses. The results showed that under different NaCI concentrations, the relative height in- crement and the relative diameter increment of L. indica were restrained obviously; the contents of chlorophyll a, chlorophyll b, carotenoid and GSH decreased with in- crease of NaCI concentration; and the content of MDA increased with increase of NaCI concentration. Through the determination and comparison of physiological in- dexes, and analysis of correlativity, NaCI tolerance of the three new L. indica vari- eties ranked as L. indica ＇Pink Velour＇〉L. indica ＇Dynamite＇〉L. indica ＇Red Rock- et＇. This is consistent with the results of the morphological characteristics after Na- CI stress.

Effects of 1-aminobenzotriazole on the growth and physiological characteristics of Tamarix chinensis cuttings under salt stress

vegetation restoration is a main ecological remediation technology for greening saline and alkaline soils.The objectives of this study were to determine the effect of1-aminobenzotriazole(ABT-1) on the growth and physiology of Tamarix chinensis under salt stress and to determine a suitable ABT-1 concentration and soil salinity(Sc) for propagating T.chihehsis-cuttings.Cuttings were soaked in water and ABT-1 solutions at three concentrations(50,100,and 200 mg L^(-1)) and propagated in pots containing four soil salinity levels,mild(0.3%),moderate(0.6%),and severe(0.9% and 1.2%),and compared with a control.The cuttings were measured to determine growth indices and physiological and biochemical indices(e.g.,chlorophyll content,superoxide dismutase activity,peroxidase activity,and malondialdehyde content).ABT-1 was effective in improving survival,growth,and physiological processes of cuttings under salt stress.However,there was a threshold effect when using ABT-1 to facilitate propagation under salt stress.ABT-1 effects were insignificant when applied at low concentrations(<100 mg L^(-1)).At a high concentration(> 100 mg L^(-1)),ABT-1 limited growth and physiological activities.Under a salt stress level(Sc ≤0.9%),ABT applied at a 100 mg L^(-1)concentration increased chlorophyll content and superoxide dismutase and peroxidase activities in the leaves and reduced malondialdehyde accumulation and membrane lipid peroxidation effects.As a result,ABT-1 enhanced the resistance of T.chinensis to salt stress.However,under high salt stress(>0.9%) and ABT-1 concentration(> 100 mg L^(-1)),the physiological regulatory ability of T.chinensis seedlings weakened.T.chinensis grew well at a salt stress ≤0.9% and ABT ≤100 mg L^(-1) and exhibited relatively high physiological regulatory ability and high salt adaptability.

Effects of Exogenous Vc on Seed Germination and Physiological Properties of Oil Sunflower(Helianthus annuus) under Salt Stress

[Objective] This study aimed to provide the theoretical and technical basis for alleviating salt damages in production practice of oil sunflower （Helianthus annuus）. [Method] Seeds of oil sunflower were used as experimental materials and treated with 120 mmol/L NaCI solution and 0-200 mg/L Vc solution during the germina- tion process, to investigate the effects of exogenous Vc on seed germination and physiological properties of oil sunflower under salt stress. [Result] Under salt stress, with the increase of Vc concentration, germination potential and germination rate of oil sunflower seeds, superoxide dismutase （SOD） and peroxidase （POD） activities and proline （Pro） content of oil sunflower seedlings increased first and then declined, which reached the maixmum in 80 mg/L Vc treatment, 120 mg/L Vc treatment and 80 mg/L Vc treatment, respectively; malondialdehyde （MDA） content of oil sunflower seedlings declined first and then increased, which reached the minimum in 160 mg/L Vc treatment. [Conclusion] To varying degrees, Vc could improve germination potential and germination rate of oil sunflower seeds and promote seedling growth under salt stress, thus alleviating the damages of salt stress to seed germination and seedling growth of oil sunflower.

Effects of salt stress on rice growth, development characteristics, and the regulating ways： A review

Rice （Oryza safiva L.） is highly susceptible to the rhizosphere salinity than other cereals. High sensitivity has been ob- served, mainly at vegetative and reproductive stages in rice. It is the duty of plant physiologists to comprehend the growth, development, and physiological processes of rice plants under stress. This paper includes the overview of rice growth and developmental processes influenced by salt stress and the regulation pathways involved in these processes. It also includes the promising salt tolerance strategies, i.e., genetic modification techniques, agronomic practices to improve rice growth, yield; and role of phytohormones and their management, especially inhibition of ethylene biosynthesis by using inhibitors 1-methylcyclopropene （1-MCP）. Rice cultivation may be a first choice for improvement of salt tolerance through plant growth regulators and improved cultivation techniques. This study will significantly improve the understanding toward low rice grain yield and poor rice resistance under salt stress and will also stream scientific knowledge for effective utilization of salt affected soils by using different regulating ways.

Preliminary Study on the Adaptability of Cucumis hystrix Chakr. under Aluminum Salt Stress

[Objective] The study was carried out to research the adaptability of Cucumis hystrix Chakr.under aluminum salt stress.[Method] Using Cucumis hystrix Chakr.and three cultivated cucumbers as tested materials,the change of physiological indexes including POD activity,SOD activity,electrolyte leakage and the content of malondialdehyde（MDA）,proline（Pro）content and soluble sugar were studied.[Result] The POD activity,SOD activity,proline content and soluble sugar content of Cucumis hystrix were higher than these of cultivated cucumbers,while electrolyte leakage and MDA content were lower,and it showed that Cucumis hystrix had better adaptability under aluminum salt stress.[Conclusion] Our study could lay a foundation for the improvement of cultivated cucumber by using the excellent characteristics of Cucumis hystrix.

Effects of Different Arbuscular Mycorrhizal Fungi on Physiology of Viola prionantha under Salt Stress

Arbuscular mycorrhizal(AM)fungi distribute widely in natural habits and play a variety of ecological functions.In order to test the physiological response to salt stress mediated by different AM fungi,Viola prionantha was selected as the host,the dominant AM fungus in the rhizosphere of V.philippica growing in Songnen saline-alkali grassland,Rhizophagus irregularis,and their mixtures were used as inoculants,and NaCl stress was applied after the roots were colonized.The results showed that V.philippica could be colonized by AM fungi in the field and the colonization rate ranged from 73.33%to 96.67%,and Claroideoglomus etunicatum was identified as the dominant AM fungi species in the rhizosphere of V.philippica by morphology combined with sequencing for AM fungal AML1/AML2 target.Inoculation with both the species resulted in the formation of mycorrhizal symbiosis(the colonization rate was more than 70%)and AM fungi significantly enhanced plants’tolerance to salt stress of varying magnitude.Higher activity of antioxidant enzymes and augmented levels of proline and other osmoregulators were observed in AM plants.The content of MDA in CK was higher than that in the inoculations with the stress of 100,200,and 250 mM.All indices except soluble protein content and MDA content were significantly correlated with AM fungal colonization indices.The analysis for different AM fungal effects showed that the mixtures and R.irregularis worked even better than C.etunicatum.These results will provide theoretical support for the exploration and screening of salt-tolerant AM fungi species and also for the application of AM-ornamental plants in saline-alkali urban greening.

G-protein β subunit AGB1 positively regulates salt stress tolerance in Arabidopsis

The heterotrimeric GTP-binding proteins（G-proteins） in eukaryotes consisted of α, β and γ subunits and are important in molecular signaling by interacting with G-protein-coupled receptors（GPCR）, on which to transduce signaling into the cytoplast through appropriate downstream effectors. However, downstream effectors regulated by the G-proteins in plants are currently not well defined. In this study, the transcripts of AGB1, a G protein β subunit gene in Arabidopsis were found to be down-regulated by cold and heat, but up-regulated by high salt stress treatment. AGB1 mutant（agb1-2） was more sensitive to high salt stress than wild-type（WT）. Compared with WT, the cotyledon greening rates, fresh weight, root length, seedling germination rates and survival rates decreased more rapidly in agb1-2 along with increasing concentrations of Na Cl in normal（MS） medium. Physiological characteristic analysis showed that compared to WT, the contents of chlorophyll, relative proline accumulation and peroxidase（POD） were reduced, whereas the malonaldehyde（MDA） content and concentration ratio of Na＋/K＋ were increased in agb1-2 under salt stress condition. Further studies on the expression of several stress inducible genes associated with above physiological processes were investigated, and the results revealed that the expressions of genes related to proline biosynthesis, oxidative stress response, Na＋ homeostasis, stress- and ABAresponses were lower in agb1-2 than in WT, suggesting that those genes are possible downstream genes of AGB1 and that their changed expression plays an important role in determining phenotypic and physiologic traits in agb1-2. Taken together, these findings indicate that AGB1 positively regulates salt tolerance in Arabidopsis through its modulation of genes transcription related to proline biosynthesis, oxidative stress, ion homeostasis, stress- and ABA-responses.

Salt Stress Effects on Germination, Plant Growth and Accumulation of Metabolites in Five Leguminous Plants

The investigation was conducted to determine physiological criteria of early selection for salt tolerant leguminous plants. Plants were subjected to 5 levels of salt stress at the roots （0, 50, 100,150 and 200 mM NaCI）. Results showed that sodium chloride had an underrating effect on growth of stems and seed germination of the species studied. The germination rates of seeds of Glycine max and Phaseolus vulgaris （sensitive glyeophytes） were affected from 3 g/L of NaCl, with critical thresholds at 9 and 12 g/L respectively. In contrast, critical thresholds with Mucunapoggei （facultative halophyte）, Vigna unguiculata （moderately tolerant glycophyte） and P. adenanthus （natural halophyte） was found to be above 21 g/L. The reduction of stems growth rate were not significant in P. adenanthus whereas in M. poggei and V. unguiculata this inhibition was observed just when nutritive solutions were enriched with 200 mM. The lipid contents were reduced in all the species under salt stress, whereas proteins and proline contents in the leaves were substantially increased in tolerant species （M. poggei, P. adenanthus and V. unguiculata）. In contrast, proteins and leaf proline contents were negatively affected by salt concentration to G. max and P. vulgaris. Seed germination, proteins and proline could be used as physiological criteria of early selection for salt tolerant leguminous plants.

Effect of Lead Stress on Growth Characteristics and Physiological Indexes of Alternanthera philoxeroides

[Objective] The paper aimed to discuss effects of different concentrations of lead stress on Alternanthera philoxeroides growth and physiological indices,to explore phytoremediation methods for removal of lead pollution. [Method] A. philoxeroides in water culture was treated with different concentration of lead,and then,its external injury was observed,its growth and physiological indexes were measured. [Result] A. philoxeroides biomass and chlorophyll content decreased; conductivity and malonaldehyde （MDA ） content were increased; the SOD,POD and CAT activities showed a trend of first increase and then decrease with increase in concentration of lead stress. [Conclusion] With increase in lead concentration,the cell membrane permeability increased and MDA had a higher accumulation,antioxidant enzymes activity decreased,the normal oxidative metabolism of A. philoxeroides was severely affected,leading it to wilt.

Effects of Antimony Stress on Photosynthetic Characteristics of Vegetable Leaves

[Objective] This study aimed to investigate the effects of different concen- trations of antimony and modifier calcium magnesium phosphate on photosynthetic characteristics of edible amaranth, flowering Chinese cabbage, spinach and flowering Chinese cabbage. [Method] By outdoor potting simulation experiment, soil matrixes containing 10.00, 20.00, 50.00, 70.00 and 100.00 mg/kg antimony （Sb3＋） were pre- pared; soil without antimony was used as control （CK）. Each pot was loaded with 0.10 kg/kg vegetable special fertilizer, mixed evenly, and divided into two shares： one share was supplemented with 1.75 g/kg modifier calcium magnesium phosphate and mixed evenly; the other share contained no calcium magnesium phosphate. Af- ter the generation of three true leaves, seedlings with uniform growth were trans- planted into the prepared soil matrixes, eights seedlings per pot. Vegetable seedlings were watered regularly to maintain 70% of field capacity. After 45 d, veg- etable plants were harvested and washed clean with distilled water for measurement of indicators of photosynthetic characteristics. [Result] With the increase of antimony concentration, relative chlorophyll content （SPAD value） and net photosynthetic rate of four vegetable species increased first and then declined, while stomatal conduc- tance of vegetable leaves was linearly reduced. [Conclusion] Appropriately adding modifier calcium magnesium phosphate can effectively improve the photosynthetic characteristics of four vegetable species and reduce the toxic effects of heavy metal antimony on vegetables.

Salt tolerance in rice:Physiological responses and molecular mechanisms

Crop yield loss due to soil salinization is an increasing threat to agriculture worldwide.Salt stress drastically affects the growth,development,and grain productivity of rice(Oryza sativa L.),and the improvement of rice tolerance to salt stress is a desirable approach for meeting increasing food demand.The main contributors to salt toxicity at a global scale are Na^(+)and Cl^(-)ions,which affect up to 50%of irrigated soils.Plant responses to salt stress occur at the organismic,cellular,and molecular levels and are pleiotropic,involving(1)maintenance of ionic homeostasis,(2)osmotic adjustment,(3)ROS scavenging,and(4)nutritional balance.In this review,we discuss recent research progress on these four aspects of plant physiological response,with particular attention to hormonal and gene expression regulation and salt tolerance signaling pathways in rice.The information summarized here will be useful for accelerating the breeding of salt-tolerant rice.

GmGPDH12,a mitochondrial FAD-GPDH from soybean, increases salt and osmotic stress resistance by modulating redox state and respiration

In plants,glycerol-3-phosphate dehydrogenase(GPDH)catalyzes the interconversion of glycerol-3-phosphate(G3P)and dihydroxyacetone phosphate(DHAP)coupled to the reduction/oxidation of the nicotinamide adenine dinucleotide(NADH)pool,and plays a central role in glycerolipid metabolism and stress response.Previous studies have focused mainly on the NAD+-dependent GPDH isoforms,neglecting the role of flavin adenine dinucleotide(FAD)-dependent GPDHs.We isolated and characterized three mitochondrialtargeted FAD-GPDHs in soybean,of which one isoform(GmGPDH12)showed a significant transcriptional response to NaCl and mannitol treatments,suggesting the existence of a major FAD-GPDH isoform acting in soybean responses to salt and osmotic stress.An enzyme kinetic assay showed that the purified GmGPDH12 protein possessed the capacity to oxidize G3P to DHAP in the presence of FAD.Overexpression and RNA interference of GmGPDH12 in soybean hairy roots resulted in elevated tolerance and sensitivity to salt and osmotic stress,respectively.G3P contents were significantly lower in GmGPDH12-overexpressing hair roots and higher in knockdown hair roots,indicating that GmGPDH12 was essential for G3P catabolism.A significant perturbation in redox status of NADH,ascorbic acid(ASA)and glutathione(GSH)pools was observed in GmGPDH12-knockdown plants under stress conditions.The impaired redox balance was manifested by higher reactive oxygen species generation and consequent cell damage or death;however,overexpressing plants showed the opposite results for these traits.GmGPDH12 overexpression contributed to maintaining constant respiration rates under salt or osmotic stress by regulating mRNA levels of key mitochondrial respiratory enzymes.This study provides new evidence for the roles of mitochondria-localized GmGPDH12 in conferring resistance to salt or osmotic stress by maintaining cellular redox homeostasis,protecting cells and respiration from oxidative injury.

Physiological Responses of Dendrobium officinale under Exposure to Cold Stress with Two Cultivars

This study aimed to explore the cold tolerance of two cultivars of Dendrobium officinale(MG1,MG2)grown in different regions of China.Under-2℃ incubation,cultivar MG1 remained active after 3 d,and continued to grow after returning to room temperature.However,MG2 could only maintain its activity after 2 d treatment at−2℃,and the seedlings died with the low temperature treatment time.Investigation of the characteristics of the plants grown in the south(Hangzhou)or north(Zhengzhou)of China indicated that the leaves of MG1 also had reduced stomatal density,the highest thickness,and a compact microstructure.The contents of proline and soluble sugars were higher in MG1 than those in MG2.The cultivar MG1 had higher SOD enzyme activity than MG2,while CAT and POD activities in samples from Zhengzhou were higher than those from Hangzhou.The contents of polysaccharides and alkaloids in stems of in MG1 were higher than those in MG2,while the content of flavonoids in the Zhengzhou samples was higher than that in the Hangzhou samples.In addition,plant heights,stem diameters,and chlorophyll content were higher in MG1.Overall,MG1 had better cold resistance than MG2.MG1 is a cold tolerant cultivar with thick leaves and reduced stomatal density,higher contents of soluble sugars,proline,CAT,POD,polysaccharides,flavonoids and alkaloids,which together make it more adaptable to low temperatures.Thus,the cultivar MG1,with its demonstrated cold tolerance,can accordingly be grown on a large scale in cold regions,thereby expanding the available planting area for this important traditional medicinal plant to meet the increasing commercial demand for it.

Effects of NaCl and NaHCO3 Stress on Photosynthesis and Chlorophyll Fluorescence Characteristics of Hemerocallis fulva ‘Golden Doll’

With Hemerocallis fulva‘Golden Doll'as an experimental material,the effects of different concentrations of neutral salt( NaCl) and alkaline salt( NaHCO3) stresses on photosynthesis and chlorophyll fluorescence characteristics in H. fulva seedlings were studied. The results showed that salt stress treatment significantly reduced the photosynthetic capacity of H. fulva. Under the NaCl and NaHCO3 stresses,the photosynthetic characteristics and chlorophyll fluorescence parameters of H. fulva seedlings were basically the same,but the photosynthetic characteristics and chlorophyll fluorescence parameter values of H. fulva seedlings were significantly different under different salt types and salt concentrations. With the extension of days of salt stress and the increase of salt concentration,the initial fluorescence yield( Fo) and non-photochemical quenching coefficient( NPQ) increased;the maximum fluorescence yield( Fm),maximum photochemical efficiency( Fv/Fm),PSII actual photosynthetic quantum yield( Y) and apparent quantum efficiency( AQY) all showed a downward trend;and moreover,with the extension of days of salt stress and the increase of salt concentration,the net photosynthetic rate( Pn) decreased and the intercellular CO2 concentration( Ci) increased. It was speculated that under salt stress,the photosynthetic characteristics of H. fulva leaves were inhibited. On the one hand,the non-stomatal limiting factor,i. e.,the chlorophyll content decreased,which led to the inhibition of photosynthetic characteristics. On the other hand,the decrease in the photosynthetic performance of mesophyll cells led to a decrease in the net photosynthetic rate of H. fulva. The changes of photosynthetic characteristics and chlorophyll fluorescence parameters in H. fulva caused by salt stress were closely related to the types of salts and salt concentration. High salt stress significantly inhibited the photosynthetic capacity of H. fulva‘Golden Doll',and the effect of NaHCO3 on H. fulva seedlings was significantly greater than that of NaCl.

Photosynthetic Physiological Response to Drought Stress of Populus euphratica at Different Ages in Minqin

[Objectives]This study was conducted to investigate the photosynthetic physiological characteristics of Populus euphratica trees at different forest ages in the desert area of Minqin in response to drought stress.[Methods]With P.euphratica trees of different ages in Minqin as the research object,the water characteristics and photosynthetic physiological indexes(chlorophyll,soluble sugar,POD,SOD and MDA)were compared under different conditions.[Results]On the time gradient,the soil water contents of P.euphratica of different ages decreased continuously with the extension of irrigation stop time,but the decreases were small.Under the same stress treatment,the soil water contents of P.euphratica of different ages increased with the deepening of soil layer,but the differences were not significant(P>0.05).Under normal condition,the chlorophyll contents of P.euphratica at three ages gradually increased with the increase of age.The chlorophyll contents in leaves of P.euphratica at different ages were all lower under normal condition and higher under water stress.The changes of POD and SOD activity in leaves of P.euphratica at different ages under different conditions were basically the same,showing that the enzyme activity was higher under water stress than under normal under.The MDA contents in leaves of the young and middle P.euphratica forests were higher under water stress at 7 and 21 d than under normal condition,and the differences were not significant(P>0.05);and the MDA content in leaves of the mature P.euphratica forest was higher under water stress at 21 and 35 d than under normal condition.Drought stress has a certain effect on the photosynthetic physiological characteristics of P.euphratica.In summary,under drought stress,the chlorophyll content,SOD and POD activity,and MDA molar concentration in the leaves of P.euphratica were basically higher than under normal condition,indicating that P.euphratica could resist drought environment through osmotic adjustment and showed strong drought resistance.[Conclusions]This study provides a theoretical reference for the restoration,protection and reconstruction of natural P.euphratica forests in the desert area of Minqin.

Distinct Morpho-Physiological Responses of Maize to Salinity Stress

Most plants demonstrate wide interactive and complex adaptive morphological, biochemical, and physiological responses when subjected to salinity stress. Salt stress negatively impacts agricultural yields more especially cultivated crops throughout the world. Of interest to this study is maize a salt- sensitive crop that is widely grown worldwide, and receiving most attention due to its significant attributes and ability to serve as a great model for stress response studies. We exposed QN701 maize cultivar, to simulated salinity stress and investigated its morphological and physiological responses. Salinity negatively induced various morphological responses such as the reduction in plant height, number of leaves, shoot and root (length and biomass), and leaf width;however, it significantly increased the leaf area. On the physiological aspect, salt stress decreased the number of stomata, stomatal density, and photosynthesis, while it increased the respiration rate. This study expanded our knowledge of the morphological and physiological responses of maize to salinity stress. Additionally, these findings may serve as a recommendation for salinity breeding programs in maize and related cereal crops.

Effect of Different Rootstocks on the Salt Stress Tolerance in Watermelon Seedlings

The selection of salt-tolerant watermelon rootstocks requires the evaluation of its underlying mechanism. The present study investigated the effect of applying 200 mmol·L-1 NaCl on various physiological and biochemical parameters of Citrullus lanatus ‘Jingxin No.2'(abbreviated as W) seedlings grafted onto W, Cucurbita moschata ‘Quanneng Tiejia'(P1), ‘Kaijia No.1'(P2), and Lagenaria siceraria ‘Hanzhen No.3'(G), which were grown hydroponically. All the measured growth parameters were significantly inhibited by salt stress, with W/P2 exhibiting superior growth. Salt stress increased Na+uptake, which in turn disrupted K+/Na+homeostasis in all grafting combinations. The photosynthetic capacity, chlorophyll concentration, and photochemical efficiency of photosystem II of all grafts significantly decreased with salt stress. However, W grafted onto G and P2 showed higher resistance than W grafted onto W and P1. Electrolyte leakage(EL) superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase activity were significantly affected by both grafting and salt stress. Minimum EL was observed in W/P2, which also exhibited superior antioxidative capacity. Physiological and biochemical assessment indicated that W grafted onto the P2 rootstock displayed the greatest salt tolerance. Plants grafted onto salt-resistant P2 accumulated less Na+and reactive oxygen species(ROS) and exhibited superior growth,photosynthesis, and ROS-scavenging capacity compared to those grafted onto the other rootstocks.

Physiological Response of Space Flight Mutation New Strains of Festuca arundinacea to High Temperature Stress and Comprehensive Evaluation

[Objective] The paper was to understand the physiological response of space flight mutation new strains of Festuca arundinacea to high temperature stress. [Method] The influence of high temperature stress on eco-physiological characteristics of 11 F. arundinacea materials was studied in a pot experiment.Physiological and biochemical indexes,including soluble protein content,superoxide dismutase( SOD),peroxidase( POD) and catalase( CAT) activities,were measured and analyzed once every 4 d for a total of three times. Subordinate function and grey rational analysis were used to comprehensively evaluate the heat resistance of 11 materials. [Result] The soluble protein content decreased with the extension of heat resistance stress,while SOD,POD and CAT activities showed an upward trend. The high temperature resistance of 11 F. arundinacea materials was evaluated by subordinate function method. The resistance order was SP5-85> SP5-60 > SP5-71 > SP5-42 > SP5-94 > SP5-7 > SP5-88 > F. arundinacea cv Shuicheng > SP5-5 > SP5-89 = F. arundinacea cv Qiancao No. 1. The relational order of various heat resistance indexes and heat resistance obtained by grey rational analysis was SOD > CAT > POD > soluble protein content. [Conclusion]The result provides a theoretical basis for stress physiology and stress breeding of cold season grass in southwest region.

Effects on Zinc Stress on Stress-Resistance Physiological and Biochemical Indexes of Jatropha curcas seedlings

Jatropha curcas seedlings were cultured for 21 d under 6 zinc concentrations of 0,25,50,100,200,400 mg/l to study the effects of ZnS O4 stress on the mechanism of resistance to heavy metal stress of J. curcas seedlings. The results showed that with the increase of stress concentration,the content of chlorophyll-a decreased and the activity of POD first increased and then maintained at a certain level or decreased slowly. The contents of soluble sugar,malondialdehyde,soluble protein and free proline increased,and the root activity increased first and then decreased. The relative conductivity of J. curcas seedlings decreased first and then increased,which indicated that the leaves of J. curcas seedlings had some adaptability and self-repairing capability under zinc toxicity stress,but the adaptability and self-repair ability were limited.

外源褪黑素与乙烯交互对盐胁迫下紫花苜蓿幼苗生长和生理特性的影响

为明确外源褪黑素和乙烯在调控植物耐盐性方面的交互作用,以‘中苜一号’紫花苜蓿为试验材料,通过叶面喷施褪黑素、乙烯利和褪黑素+乙烯利的方法,研究外源施加褪黑素和乙烯对盐胁迫下紫花苜蓿幼苗生长和生理特性的影响。结果表明:外源施加一系列浓度的褪黑素处理(0.01、0.02、0.05、0.10 mmol·L^(-1) MT)和乙烯利处理(0.05、0.15、0.25、0.50 mmol·L^(-1) ETH)均对盐胁迫下(250 mmol·L^(-1) NaCl)紫花苜蓿幼苗的生长损伤具有缓解作用,并以0.05 mmol·L^(-1)褪黑素处理和0.15 mmol·L^(-1)乙烯利处理缓解效果最佳,其幼苗株高、叶面积、鲜重、叶绿素含量和类胡萝卜素含量显著增加,相对电导率显著降低。采用以上最佳处理浓度试验发现:与对照组相比,盐胁迫下紫花苜蓿幼苗的生长明显被抑制;与单独盐处理组相比,外源施加激素后紫花苜蓿幼苗长势明显较好,尤其是同时施加褪黑素和乙烯利时,紫花苜蓿幼苗的株高、叶面积和鲜重分别增加了54.1%、76.8%和32.1%,组织含水量和叶绿素含量分别增加了46.2%和47.8%,相对电导率和丙二醛含量分别降低了23.5%和39.7%,过氧化氢和超氧阴离子含量分别减少了42.7%和63.8%,超氧化物歧化酶SOD、过氧化物酶POD、过氧化氢酶CAT和抗坏血酸过氧化物酶APX活性分别增加了54.1%、54.1%、59.1%和62.0%,还原性谷胱甘肽GSH含量增加32.8%,脯氨酸和可溶性糖含量增加了42.2%和27.2%,钾钠离子比值增加了217.5%,植株内源褪黑素和乙烯含量分别增加了60.0%和10.6%。综合分析表明,外源施加褪黑素和乙烯能够显著降低紫花苜蓿膜脂过氧化水平和活性氧积累,增加抗氧化酶活性和渗透调节物质含量,调控植株体内离子平衡,增加幼苗内源激素含量,提高紫花苜蓿幼苗的耐盐性,从而促进盐胁迫下幼苗的生长。