硅提高黄瓜幼苗抗盐能力的生理机制研究

为了明确硅提高黄瓜幼苗抗盐能力的机制,该试验采用水培方法,以黄瓜品种‘津优一号’为材料,对幼苗进行中度盐胁迫,研究在盐胁迫下硅对黄瓜幼苗生长、光合特性、渗透调节物质和离子吸收的影响。结果显示:(1)正常条件下,硅对黄瓜幼苗生长及相关生理指标无明显影响;单独盐处理降低了幼苗叶片叶绿素含量、光合速率、气孔导度、蒸腾速率和叶片含水量,导致幼苗生长受抑。(2)盐胁迫下加硅显著提高了幼苗光合速率和叶片含水量,增加了生物量的积累;在盐胁迫初期,硅加盐处理黄瓜叶片渗透势略低于单独盐处理,此后均高于单独盐处理;硅加盐处理显著提高了叶片可溶性糖含量,尤其是蔗糖含量,而降低了其脯氨酸含量,但对可溶性蛋白含量无显著影响。(3)盐胁迫下黄瓜植株Na+含量大幅上升,K+含量下降,K+/Na+比大幅降低;硅加盐处理降低了黄瓜叶片中Na+含量,提高了K+含量和K+/Na+比。研究表明,盐胁迫条件下,硅能通过减轻叶片离子毒害和增加水分吸收,改善叶片水分状况,从而维持较高的光合能力,提高其抗盐能力;而渗透调节只在盐胁迫初期有轻微缓解作用,不是硅提高黄瓜幼苗抗盐性的主要途径。     

盐分胁迫下两个苋菜品种对镉及主要渗透调节物质累积的差异

采用重金属Cd平均含量为2.28 mg·kg-1的污灌菜园土,在外源Na Cl处理下进行盆栽试验,研究花红圆叶苋菜(BRLA)和红柳叶苋菜(ARW)对Cd及主要渗透调节物质吸收和积累的品种间差异。结果显示:随盐胁迫增强,两品种根、叶Cd和Na+含量较对照显著增加(P0.05),且品种ARW的Cd累积量高于品种BRLA。与ARW相比,BRLA根可贮存更多的Na+以减少向叶转运,在0.4%盐处理时BRLA叶K+/Na+比值降幅为39.2%,而ARW达56.9%。盐分促进BRLA根、叶Mg2+含量增加,而ARW根Mg2+则低于对照。盐胁迫后,两品种根、叶脯氨酸含量显著高于对照(P0.05),且BRLA表现较强的脯氨酸合成能力。两品种根、叶总游离氨基酸与可溶性蛋白含量随盐胁迫强度增大呈相反的变化。盐分促进了两品种根部可溶性糖积累。综上,BRLA比ARW具有较低Cd累积性,表现较好的耐盐性,具备较强的渗透响应能力,可为筛选和培育既耐盐又低累积Cd的农作物提供科学参考。     

莳萝蒿适应盐渍环境的Na~+区域化方式和生理特征

莳萝蒿是广泛分布在我国北方的一种特殊类型的菊科盐生植物,阐明莳萝蒿特殊的耐盐机制和生理特征有助于丰富植物抗盐性研究的内容。用0、100、200、300、400 mmol/L Na Cl处理莳萝蒿7 d后,比较莳萝蒿盐处理植株与对照植株在生长和生理方面的差异,并详细分析了Na+在莳萝蒿体内的积累水平和区域化方式。结果显示:莳萝蒿虽然能够耐受400 mmol/L Na Cl,但盐处理显著抑制了莳萝蒿的生长,整株鲜重随着盐处理浓度的升高逐渐减小。在水分生理方面,随着盐处理浓度的升高,莳萝蒿叶片细胞的渗透调节能力逐渐增强,其叶片肉质化程度却呈逐渐降低的趋势。分析盐处理对光合作用的影响发现,盐处理后莳萝蒿叶片光合速率与气孔导度显著下降,而其PSⅡ光化学活性并未受到抑制,叶绿素含量甚至逐渐增大,说明盐处理后莳萝蒿叶片光合速率的降低主要是由于气孔因素造成的,而不是由于光合结构被破坏。莳萝蒿体内的Na+含量随着盐处理浓度的升高显著增加,400 mmol/L Na Cl条件下叶、茎、根中的Na+含量分别高达321.4、242.1和182.3μmol/g鲜重;莳萝蒿体内的Na+70%以上积累在叶片内,而叶片内98%左右的Na+积累在叶片原生质体中,叶片原生质体中的Na+平均浓度是质外体1.2—1.8倍,推测其叶片细胞内存在着有效的Na+区域化机制。盐处理后莳萝蒿叶片液泡膜V-H+-ATPase的质子泵活性比对照增加了30%—50%,液泡膜Na+/H+逆向转运活性则增加至对照的4—7倍,进一步证实莳萝蒿叶片具有较强的液泡Na+区域化能力。随着盐处理浓度的升高,Na+在叶片中的分布比例相对减少,V-H+-ATPase的质子泵活性和Na+/H+逆向转运活性增幅也减缓。这种Na+区域化能力使莳萝蒿获得了较强的耐盐性,有效保护了其光系统,降低了细胞汁液渗透势。但是盐处理后这种耐盐方式并不能阻止莳萝蒿叶片肉质化程度和光合活性下降,莳萝蒿生长仍然受盐抑制,说明Na+区域化是莳萝蒿适应盐渍环境的必要条件而非充分条件。     

外源硝酸钙对黄瓜幼苗盐胁迫伤害的缓解作用

采用营养液水培法,以较耐盐黄瓜品种'新泰密刺'为试材,研究了叶面喷施硝酸钙对盐胁迫(NaCl 65 mmol·L-1)下黄瓜幼苗生长、叶绿素含量、膜脂过氧化产物丙二醛(MDA)、脯氨酸及不同部位离子含量的影响.结果表明,叶面喷施硝酸钙能够显著提高盐胁迫下黄瓜幼苗的干鲜重、相对含水量和叶片叶绿素含量,显著减少MDA及渗透调节物质脯氨酸的积累;同时可显著降低盐胁迫下黄瓜幼苗体内Na+和Cl-含量,提高K+、Ca2+含量和 K+/Na+、Ca2+/Na+.可见,外源硝酸钙能缓解盐胁迫下黄瓜幼苗的失水程度和光合色素的下降幅度,保护膜的完整性,调节离子选择性吸收,从而减轻盐胁迫伤害,促进黄瓜植株生长.     

盐生植物海马齿耐盐的生理特性

以盐生植物海马齿为研究材料,分别用淡水、1/4海水、1/2海水、全海水浇灌15 d和30 d,研究盐生植物耐盐的生理特性和机理。海马齿植物在低于1/2的海水浇灌时,植物生长旺盛,主要表现为叶片增大和变厚,地上部分生物量增加;而全海水抑制了植物的生长。在盐胁迫下,海马齿植物中Na+的含量叶中最高,茎中含量次之,根中含量最低。长时间盐胁迫时,海马齿植物根、茎、叶中的相对含水量与淡水浇灌相比,变化不大,叶中略有增加;而脯氨酸含量显著增加,且可溶性糖的含量也比淡水浇灌的高。由此推测:海马齿植物主要以有机小分子作为渗透调节物质来维持细胞渗透压,在其耐盐中起着重要的作用。土壤中Na+的毒害,并没有减少土壤中可被植物利用的可交换K+,反而使其增加,说明海马齿植物根部对Na+的吸收能力和Na+/K+交换能力非常强。海马齿植物耐盐性强,还表现为能阻止盐胁迫对植物细胞原生质膜的氧化损伤,不破坏植物叶片内叶绿素的合成,能基本维持植物茎、叶中K+和根、茎中Mg2+的相对稳定。     

披针叶黄华试管苗适应盐胁迫的渗透调节机制

以披针叶黄华(Thermopsis lanceolata)试管苗为材料,通过组培方法研究其在0、0.2%、0.4%、0.6%、0.8%和1.0%NaCl和Na2SO4胁迫30d后的生长、有机渗透调节物质和无机渗透调节物质(Na+、K+和Ca2+)含量的变化,以探讨其耐盐性机制。结果显示:(1)随NaCl和Na2SO4胁迫浓度的增加,披针叶黄华试管苗叶片脯氨酸和可溶性糖含量均显著持续增加,且NaCl胁迫下脯氨酸上升的幅度均大于相同浓度Na2SO4胁迫下的增幅,而可溶性糖上升的幅度却小于相同浓度Na2SO4胁迫下的幅度;可溶性蛋白含量随NaCl浓度的增大呈先升高后降低的趋势,但随Na2SO4浓度的增加呈持续上升的趋势。(2)随NaCl和Na2SO4浓度的增加,披针叶黄华试管苗Na+含量呈增加趋势且各处理均显著高于对照,Ca2+含量和叶片K+含量却呈逐渐减少趋势且各处理均显著低于对照,而根系K+含量呈先降后升的趋势;Na2SO4胁迫下披针叶黄华试管苗叶片Na+含量上升幅度以及K+和Ca2+含量下降幅度均明显低于相同浓度NaCl胁迫组;而Na+/K+和Na+/Ca2+比值随NaCl和Na2SO4浓度增加而升高;NaCl胁迫下,叶片Na+/K+和Na+/Ca2+高于相同浓度Na2SO4胁迫下的比值,而根系Na+/K+和Na+/Ca2+却低于相同浓度Na2SO4胁迫下的比值。研究表明,盐胁迫下,披针叶黄华试管苗通过抑制叶片中Na+积累并增加可溶性糖和可溶性蛋白含量,在根系中维持较高K+和Ca2+含量以及较低水平Na+/K+和Na+/Ca2+比,以降低披针叶黄华细胞渗透势来适应盐渍环境;披针叶黄华对NaCl胁迫的调节能力弱于Na2SO4。     

盐胁迫下盐地碱蓬体内无机离子含量分布特点的研究

用不同浓度NaCl溶液处理盐地碱蓬（Suaeda salsa)植株后,测定并比较老叶、幼叶及根部的无机离子含量和对K的选择性,叶片及根部的Na^ 、Cl^-含量随盐度的增加而升高,且累积趋势相似,盐胁迫下根部Na^ 、Cl^-及总离子含量（K^ 、Na^ 、Ca^2 ,NO3^-,Cl^-)明显低于叶片,说明盐地碱蓬地盐胁迫下,以叶片优先积累大量离子（如Na^ ,Cl^-) 为其适应特征。NaCl处理下,叶片的K^ ,Ca^2 含量低于对照,但随盐度的增加保持相对稳定,而根部K^ 含量,K/Na比、对K的选择性则高于叶片,这对盐胁迫下地上部的K^ 亏缺有一定补偿作用。低盐度处理（100mmol/LNaCl)促进NO3^-的吸收,另外随盐度的增加,叶片渗透势下降,渗透调节能力增强,幼叶渗透势低于老叶,但渗透调节能力相同。     

胡杨披针形叶与宽卵形叶的渗透调节能力的差异

以胡杨披针形叶和宽卵形叶作为实验材料,对其组织水平的离子含量及不同类型细胞的离子分布特征、可溶性有机渗透调节物质的含量、液泡膜H+-ATPase的活性进行了测定。结果表明,Na+、Cl-、K+、Ca2+等离子的分布在两种叶片及不同细胞中有差异,主要表现为宽卵形叶中Na+、Cl-的含量分别为披针形叶的111.2%和118.4%,Na/K值和Na/Ca值分别为0.75和1.78,均高于披针形叶的。宽卵形叶的栅栏细胞的Na/K值和Na/Ca值较其维管束鞘细胞的高,而披针形叶的则正相反;宽卵形叶较披针形叶含有较高浓度的可溶性糖和脯氨酸,分别为514和0.751μmol·g-1FW,而甜菜碱的含量较低,为0.703μmol·g-1FW;宽卵形叶的液泡膜H+-ATPase的活性较披针形叶的高15.47%。以上结果表明胡杨宽卵形叶的渗透调节能力较强于披针形叶。本文还对两种叶片对胡杨适应其盐渍化生境的贡献进行了讨论。     

盐胁迫下水稻苗期Na+和K+吸收与分配规律的初步研究

选择苗期耐盐性较强的水稻(Oryza sativa)品种(株系)'AB52'、'02402'和'02435'及敏感品种'日本晴',在网室周转箱内,设置5 000和8 000 mg·L-1NaCl两种盐处理,以清水为对照,研究盐胁迫下苗期水稻植株不同部位Na+和K+的吸收和分配与品种耐盐性的关系.结果表明,盐胁迫下,株高、绿叶干重和绿叶面积下降,绿叶中的水分含量降低,但茎鞘中的水分含量有所上升.5 000 mg·L-1NaCl胁迫处理10 d,耐盐品种所受的生长影响和叶片伤害程度低于敏感品种,但8 000 mg·L-1NaCl胁迫处理下品种间差异变小.盐胁迫下,水稻植株吸收Na+和置换出K+,但不同器官部位中Na+和K+的区域化分布特征明显,各部位的Na+含量由低到高依次为绿叶、根、茎鞘和枯叶.下部老叶能优先积累较多Na+而枯黄;绿叶吸收Na+相对较少,维持较低的Na+水平,同时保持较高且稳定的K+含量;植株茎鞘通过选择性吸收大量Na+和置换出一部分K+到叶片中,保持绿叶较稳定的K+含量和相对较低的Na+含量,维持较高的K+/Na+比,从而使植株少受盐害.敏感品种'日本晴'在盐胁迫下绿叶中的Na+含量相对较高,且5 000 mg·L-1NaCl胁迫下绿叶Na+含量已接近高值,与在8 000 mg·L-1NaCl胁迫下差异不大,而耐盐品种绿叶吸收较少的Na+.另一方面,耐盐品种茎鞘的含K+相对较高,在盐胁迫下能吸收容纳较多的Na+,而绿叶中K+/Na+比较高.可以认为,绿叶的K+/Na+比可作为一个衡量耐盐性的相对指标.     

丛枝菌根真菌Glomus mosseae对盐胁迫下牡丹渗透调节的影响

以采自菏泽牡丹园的牡丹‘凤丹’为材料,采用盆栽方法研究了不同浓度人工海水（0%、8%、16%和24%）胁迫下,接种丛枝菌根（arbuscular mycorrhizal,AM）真菌Glomus mosseae对牡丹渗透调节物质含量的影响,以不接种为对照。结果表明,盐胁迫下接种AM真菌能提高牡丹叶片可溶性糖和可溶性蛋白的含量,增大K＋/Na＋比值,减少叶片脯氨酸含量。结论认为,AM真菌能改善牡丹叶片的渗透调节,增强牡丹耐盐能力,促进了盐胁迫下牡丹幼苗的生长。     

Growth Adaptability and Salt Tolerance Osmoregulation of Aneurolepidium chinense Grown on Saline Grassland

The growth of Aneurolepidium chinense Kitag. grown on different saline soil of a Northeast grassland of China was studied and the K+,Na+proline and citric acid accumulated in plants or their organs were determined . The results showed that A. chinense had a strong adaptability to saline habitat and could grow on soil with a salt content of 0. 088%--1.63%,and pH ranging from 8.3 to 9.8. Sodium,proline and citric acid were accumulated by plants for osmotic adjustment when the salinity and Na+content of the soil increased. A. chinense absorbed Na+ rapidly from the soil and excluded K+ when the soil Na+ concentration was less than 20 μmol/g. Sodium was adsorbed slowly and K+ remained constant in plants when Na+ concentrations of soil were 20–80 μmol/g,and proline and citric acid contents were markedly increased. Sodium and K+ decreased slightly in plant tissue and organic solutes increased when Na+ concentrations exceeded 80 μmol/g in soil. Most K+ was distributed in young leaves which were metabolically active. The major sites of Na+ accumulation were in the roots and older mature leaves;whereas proline and citric acid accumulation occurred primarily in young leaves,mature leaves and stems. Tillering buds had strong ability to absord and accumulate K+,Na+ and Proline.     

Proline accumulation by tomato leaf tissue in response to salinity

The capacity of tomato leaf tissues to accumulate proline in response to a salt shock (150 mM NaCl) applied to excised shoots, leaves, leaflets or leaf discs was determined and compared to that of whole plants grown at the same salinity. The associated changes in free amino acids, Na+, K+ and Cl- contents were also investigated. In excised organs treated for 80 h, up to 200 mumol g-1 DW of proline were accumulated, whereas the amount of proline in leaf discs did not exceed a value ten-fold lower. In the whole plants subjected to salinity the Na+, Cl- and K+ contents remained low in comparison to that observed in excised organs. Proline and other amino acids increased more slowly in whole plants than in excised shoots. The contribution of roots and vascular tissues to the control of Na+ and Cl- accumulation and to the regulation of proline metabolism are discussed.     

半根和全根干旱对嘎拉苹果组培苗渗透调节物质积累的影响

以1年生苹果组培苗为试验材料,用改良的Hoagland营养液加20％聚乙二醇6000进行半根渗透胁迫（HRS）处理,与全根渗透胁迫（WRS）和只加营养液的对照（CK）进行比较,研究了根系不均匀供水条件下植株的叶片水势、脯氨酸、游离氨基酸、町溶性糖、淀粉等几种有机溶质,以及Na^-、K^-、Mg^2＋、Ca^2＋、Cl^-、SO4^2-、NO3^-等无机离子的含量变化特点。结果表明,HRS与CK之问叶片的日出前水势不存在显著差异,但显著高于WRS。叶片的日出前水势与叶片中脯氨酸和可溶性糖含量之间呈负相关关系,与淀粉含量之问呈正相关关系,与Na^-、K^-、Mg^2＋、Ca^2＋、Cl^-、SO4^2-、NO3^-之间没有相关关系。表明干旱胁迫后苹果幼苗叶片中脯氨酸等有机溶质参与渗透调节作用,无机离子的作用较小。HRS叶片中有机溶质没有大量积累,表明HRS植株整体的水分供应状况良好。     

Ion-specific mechanisms of osmoregulation in bean mesophyll cells

Transient kinetics of net H+, K+, Ca2+, and Cl- fluxes were measured non-invasively, using an ion-selective microelectrode technique, for bean (Vicia faba L.) leaf mesophyll in response to 150 mM mannitol treatment. In a parallel set of experiments, changes in the plasma membrane potential and the total proline content in leaves were monitored. Regardless of the ionic composition of the bath solution, hyperosmotic stress caused a significant increase in the K+ and Cl- uptake into mesophyll cells. At the same time, no significant proline changes were observed for at least 16 h after the onset of stress. Experiments with inhibitors suggested that potassium inward rectifier (KIR) channels, exhibiting mechanosensitive properties and acting as primary receptors of osmotic stress, are likely to be involved. Due to the coupling by membrane potential, changes in K+ and Cl- transport may modify activity of the plasma membrane H+-pump. Such coupling may also be responsible for the mannitol-induced oscillations (period of about 4 min) in net ion fluxes observed in 90% of plants. Calculations show that influx of K+ and Cl- observed in response to hyperosmotic treatment may provide an adequate osmotic adjustment in bean mesophyll, which suggests that the activity of the plasma membrane transporters for these ions should be targeted to improve osmotolerance, at least in this crop.     

Combined effects of long-term salinity and soil drying on growth, water relations, nutrient status and proline accumulation of Sesuvium portulacastrum

The interaction between soil drying and salinity was studied in the perennial halophyte, Sesuvium portulacastrum. Rooted cuttings were individually cultivated for three months in silty-sandy soil under two irrigation modes: 100 and 25% of field capacity (FC). The amount of the evapotranspirated water was replaced by a nutrient solution containing either 0 or 100 mM NaCl. Whole-plant growth, leaf water content, leaf water potential (Psi(w)), and Na+, K+, and proline concentrations in the tissues were measured. When individually applied, both drought and salinity significantly restricted whole-plant growth, with a more marked effect of the former stress. However, the effects of the two stresses were not additive on whole-plant biomass or on leaf expansion. Root growth was more sensitive to salt than to soil drying, the latter being even magnified by the adverse impact of salinity. Leaf water content was significantly reduced following exposure to water-deficit stress, but was less affected in salt-treated plants. When simultaneously submitted to water-deficit stress and salinity, plants displayed higher values of water and potassium use efficiencies, leaf proline and Na+ concentrations, associated with lower leaf water potential (-1.87 MPa), suggesting the ability of S. portulacastrum to use Na+ and proline for osmotic adjustment.     

Effect of Exogenous ABA on the Salt Tolerance of Corn Seedlings Under Salt Stress

The exogenous ABA in different concentrations was used to spray Zea mays L. (cv. Luyu 11) seedlings under different salinity. The growth status, osomotic potential and osmotic regulatory activity, the contents of Na+ and K+, soluble sugars and proline were determined at different time after treatment. The results were shown as follows: The exogenous ABA gave an increase in salt resistance and dry weight of corn seedlings under different salinity, this increase was as a result of inhanced osmotic adjustment activity and exclusion of sodium ions from the shoot through the action of exogenous ABA, resulting an accumulation of sodium in the roots. Moreover, the decrease of osmotic potential and the increase of osmotic regulatory activity were for reasons of enhancement of organic osmotors, instead inorganic, e.g. Na+ and K+ osmotors. The mechanism of sodium exclusion from the shoot was also discussed.     

硒对盐胁迫下耐盐常夏石竹生物量和渗透物质含量的影响

培养基中加施适量外源硒能够显著提高能耐盐的常夏石竹生物量,过氧化物酶(POD)活性,K^ ／Na^ 比值,K^ 、Na^ 、叶绿素和游离脯氨酸含量;降低质膜透性和可溶性糖含量;植株叶细胞质膜和液泡膜V-H^ -ATP酶的活性增加。     

High-affinity potassium and sodium transport systems in plants

All living cells have an absolute requirement for K+, which must be taken up from the external medium. In contrast to marine organisms, which live in a medium with an inexhaustible supply of K+, terrestrial life evolved in oligotrophic environments where the low supply of K+ limited the growth of colonizing plants. In these limiting conditions Na+ could substitute for K+ in some cellular functions, but in others it is toxic. In the vacuole, Na+ is not toxic and can undertake osmotic functions, reducing the total K+ requirements and improving growth when the lack of K+ is a limiting factor. Because of these physiological requirements, the terrestrial life of plants depends on high-affinity K+ uptake systems and benefits from high-affinity Na+ uptake systems. In plants, both systems have received extensive attention during recent years and a clear insight of their functions is emerging. Some plant HAK transporters mediate high-affinity K+ uptake in yeast, mimicking K+ uptake in roots, while other members of the same family may be K+ transporters in the tonoplast. In parallel with the HAK transporters, some HKT transporters mediate high-affinity Na+ uptake without cotransporting K+. HKT transporters have two functions: (i) to take up Na+ from the soil solution to reduce K+ requirements when K+ is a limiting factor, and (ii) to reduce Na+ accumulation in leaves by both removing Na+ from the xylem sap and loading Na+ into the phloem sap.     

Isoosmotic regulation of cotton and peanut at saline concentrations of k and na

Peanut (Arachis hypogaea L.) and cotton (Gossypium hirsutum) plants were grown for 4 weeks in saline, isoosmotic rooting substrates with different proportions of K and Na. Isoosmotic media did not affect growth (except at the highest external K concentrations) or estimates of intracellular osmotic pressure in expanding leaves (i.e. osmotic pressure of leaf sap and intracellular osmotic pressure as calculated from pressure-volume curves). In expanded leaves, an increase in the proportion of external K increased sap osmotic pressure. The sum of [K+Na+Cl] in the sap of expanding and expanded leaves accounted for the effect of isoosmotic media on the concentration of osmolytes with high electrical conductance, so the difference between sap osmotic pressure and [K+Na+Cl] accounted for the concetration of osmolytes with low conductance. In expanding leaves, an increase in the proportion of external K increased [K+Na+Cl] and decreased the concentration of osmolytes with low conductance. In expanded leaves, an increase in the proportion of external K increased [K+Na+Cl] to approximately the same extent as sap osmotic pressure. Isoosmotic regulation was apparent in expanding leaves but not evident in expanded leaves. This suggests a turgor homeostat which can influence the concentration of organic solutes in expanding leaves but cannot control the import of inorganic solutes from a rooting medium nor the total production of organic solutes in plants with a low sink:source ratio.