盐与碱胁迫对燕麦离子平衡和有机酸含量的影响

以燕麦品种‘白燕2号’为材料,试验分别设置0、50、100、150、200 mmol/L盐胁迫(NaCl∶Na₂SO₄=5∶1)和碱胁迫(NaHCO₃∶Na₂CO₃=5∶1)处理的温室内盆栽试验,观测燕麦植株生长速率、植株含水率、叶片离子含量及叶片各类有机酸含量,分析不同盐胁迫、碱胁迫对燕麦离子平衡的影响,并比较燕麦对两类胁迫的适应性差异。结果显示：(1)燕麦植株生长速率和植株含水率在低浓度(50和100 mmol/L)盐胁迫下均升高,而高浓度(150和200 mmol/L)盐胁迫下则降低;燕麦植株生长速率和植株含水率均随碱胁迫浓度增加而降低;在相同胁迫浓度下,碱胁迫对植株生长率、植株含水率的影响大于盐胁迫。(2)燕麦叶片K⁺、Ca²⁺、Mg²⁺、H₃PO^-₄、NO^-₃ 含量均随盐、碱浓度升高而降低,而Na⁺、Cl^-、SO^2-₄含量在盐、碱胁迫下均大幅上升;200 mmol/L盐、碱胁迫下,Na⁺ 含量分别较对照增加367.15%和518.41%,Cl^- 含量分别较对照增加785.07%和52.59%,SO^2-₄ 分别较对照增加142.01%和52.86%。(3)200 mmol/L盐、碱胁迫下,有机酸分别较对照增加74.52%和1 232.34%;碱胁迫及高浓度盐胁迫下燕麦叶片的柠檬酸、乌头酸、琥珀酸和苹果酸含量均高于对照,且乌头酸是燕麦响应盐胁迫、碱胁迫的主要有机酸成分,柠檬酸和琥珀酸略有变化,而甲酸、乙酸、乳酸、苹果酸、草酸含量均相对较低。研究表明,碱胁迫对燕麦植株生长速率、植株含水率、叶片离子含量及叶片各类有机酸含量的影响大于盐胁迫;盐胁迫与碱胁迫均引起燕麦叶片阳离子(Na⁺)大量积累,而K⁺、Ca²⁺、Mg²⁺、H₃PO^-₄及NO^-₃吸收受阻;燕麦叶片在盐胁迫下主要通过积累Cl^-调节叶片离子平衡,而碱胁迫下主要通过积累有机酸来调节离子平衡;有机酸是燕麦叶片响应碱胁迫的特异代谢物,其中乌头酸是其有机酸的主要成分。     

渗透胁迫和离子毒害对转Bt基因棉幼苗生长及离子分布的影响

研究了渗透和盐胁迫处理对转Bt基因抗虫棉(Gossypium hirsutum) 99B种子的萌发和幼苗生长的影响,以及幼苗不同器官离子吸收和分配的差异。结果表明:渗透和盐胁迫均对转Bt基因抗虫棉幼苗的生长有抑制作用,其中PEG的抑制作用最强,而3种盐的抑制程度以CaCl₂>NaCl>Na₂SO₄,且在Na⁺含量相同时,Cl^-的毒害大于SO₄^2-。渗透胁迫下使根、茎和叶中的Na⁺和Cl^-含量提高,K⁺、Ca²⁺、SO₄^2-含量和K⁺/Na⁺、Ca²⁺/Na⁺和SO₄^2-/Cl^-比值降低,且地上部的变化幅度大于地下部的,其中以PEG的影响最为显著,其次是CaCl₂,Na₂SO₄处理最弱。这些说明,转Bt基因抗虫棉99B的耐盐性较弱。     

黄河口湿地柽柳灌丛土壤盐渍化特征

为探究黄河三角洲湿地柽柳灌丛下土壤的盐渍化特征，在黄河三角洲国家级自然保护区(37°35''-12''N，118°33''-119°20''E)黄河入海口附近，根据长势基本一致的原则分别在碱蓬群落、柽柳群落和芦苇群落各选3株柽柳，采集柽柳灌丛下土壤样品，分析土壤盐分和盐碱化参数的空间分布以及距基茎不同距离处研究对象(土壤总盐(TS)、电导率(EC)、pH、交换性钠百分率(ESP))和环境因子(Na⁺、K⁺、Ca²⁺、Mg²⁺、Cl^-、HCO₃^-、SO^2-₄)之间的关系。结果表明：(1)研究区土壤为弱碱化盐土，离子含量由高到低依次为Cl^->Na⁺>SO^2-₄ >Ca²⁺>Mg²⁺>HCO^-₃>K⁺。除pH在土壤表层数值最低外，表层土壤TS、EC、ESP和盐分离子大于深层土壤，显示表聚性。(2)土壤盐分和盐碱化参数空间分布总体为：在柽柳基茎周围形成"盐谷"、"碱谷"效应， Na⁺、Mg²⁺、Cl^-表现为"盐谷"，K⁺ 、SO^2-₄ 、Ca²⁺ 表现为"盐岛"。(3)在整个土壤剖面中，与TS、EC相关性最强的阴阳离子为Mg²⁺、Cl^-，从灌丛中心到灌丛间裸地Ca²⁺、SO^2-₄与TS、EC的相关性逐渐减弱，Mg²⁺、Cl^-与TS、EC的相关性逐渐增强。Ca²⁺和SO^2-₄与pH表现为较强的负相关性；与ESP相关性最强的阴离子为HCO^-₃，与之相关性最强的阳离子为Na⁺和K⁺，并且Na⁺和K⁺与ESP的相关性表现出从灌丛中心向外逐渐增强。(4)土壤盐渍化主要受控于Na⁺，从灌丛下到灌丛间裸地Cl^-对盐渍化程度的影响逐渐增加，SO^2-₄的影响逐渐降低。     

不同耐盐植物根际土壤盐分的动态变化

以甘肃秦王川引大灌区盐渍化土壤为研究背景,用盆栽根袋法对4种耐盐植物根际和非根际土壤pH和盐分离子的动态变化进行了分析比较。结果表明:4种待测植物随着培养时间的延长土壤pH和EC值呈降低趋势。新疆大叶(Medicago Sativa L.cv.Xinjiangdaye)、向日葵(Helianthus annuus)和霸王(Zygophyllum xanthoxylum)生长90 d后根际土壤pH明显低于非根际,而裸麦(Hordeum vulgare var. vulgare)根际较非根际pH差异不大。霸王和新疆大叶根际土壤EC值较非根际高,而裸麦和向日葵的根际与非根际差异不大。4种供试植物根际K⁺均出现亏缺,Ca²⁺、Na⁺、Mg²⁺、SO^2-₄和Cl^-在新疆大叶、霸王和向日葵3种植物根际均出现富集,对于裸麦:Ca²⁺、Mg²⁺和SO^2-₄ 3种离子在植物根际富集,而Cl^-和Na⁺在根际亏缺。随着待测植物培养时间的增加Na⁺/K⁺、Na⁺/Ca²⁺和Na⁺/Mg²⁺ 这3个比值呈降低趋势,说明Na⁺相对于K⁺、Ca²⁺和Mg²⁺的含量降低,生物措施对Na⁺的移除效果较显著。     

荒漠盐生植物根际系统盐分分布特征

利用盐土和棉田土,采用水平根垫法对4种不同类型的荒漠盐生植物进行栽培实验,应用冰冻薄层切片法对距根表不同距离的土壤进行分层取样,并测定不同层次土壤中pH、总盐、Cl^-、SO₄^2-、Na⁺、K⁺、Ca²⁺和Mg²⁺的含量。结果表明: 在盐土中,距根表不同距离的土壤中,pH值呈有规律的梯度分布,即根际微区pH值较土体下降,且距根表越近,pH值越低;而在棉田土中却没有显著变化;总盐在根际出现较大的亏缺区,最大亏缺率位于距根表0～4 mm处;在盐土中,除芦苇外,其余3种盐生植物的根际土中Cl^-、SO₄^2-、Na⁺、K⁺、和Mg²⁺的含量在根际有明显的富集;在棉田土中,除K⁺外,这些离子在根际也有富集,但富集程度比盐土低,K⁺表现亏缺,而Ca²⁺却是富集的;4种植物尤其是稀盐盐生植物和泌盐盐生植物,地上部分的主要盐离子（如Cl^-、Na⁺、Ca²⁺和K⁺）含量比地下部分高,在根际富集程度最高的Cl^-和Na⁺,在植株的地上部分也增加的最多。     

苏干湖湿地土壤全盐含量特征及其与地下水的关联

地下水是内陆盐沼湿地生态水文过程及演变的关键因素,地下水位埋深和水质特征交互作用影响水盐运移过程和表层土壤盐渍化程度。根据2018年8月土壤盐分与地下水特征的监测数据,运用经典统计学、皮尔逊相关性和主成分分析等方法对苏干湖湿地（93°47''53″-94°04''26″E,38°50''07″-38°56''27″N）不同水位下表层0-10 cm土壤全盐含量、地下水水质特征及其间的关系进行定量分析。结果表明：（1）研究区0-10 cm土壤全盐含量的均值为204.41 g/kg,随地下水埋深的增加,土壤全盐含量的均值、变化幅度和变异系数呈先增加后降低的趋势。（2）地下水埋深介于0.17-6 m,pH在7.06-9.56范围,阳离子以Na⁺为主,阴离子以SO₄^2-和Cl^-为主,离子浓度变异系数从强到弱依次为Na⁺ > Mg²⁺ > Ca²⁺ > Cl^- > SO₄^2- > HCO₃^- > K⁺ > CO₃^2-。（3）关联分析表明,在水埋深<1 m、1-2 m的区域表层全盐含量与地下水埋深呈正相关,地下水埋深介于2-3 m和>3 m的区域两者间呈负相关;土壤全盐含量与地下水水质离子Na⁺、Mg²⁺、SO₄^2-、Cl^-间呈极显著正相关,与K⁺、CO₃^2-、HCO₃^-间的相关系数较低且不显著。内陆盐沼湿地表层土壤全盐含量与地下水埋深、地下水水质特征的关联分析,体现了内陆盐沼湿地土壤水盐运移过程的复杂性。     

盐胁迫下构树幼苗各器官中K+、Ca2+、Na+和Cl-含量分布及吸收特征

将当年生构树幼苗置于含有不同浓度（04、1、2、3、4 g·kg^-1）NaCl的土壤中,研究其生物量积累、叶片细胞质膜透性和K⁺、Ca²⁺、Na⁺、Cl^-等离子的吸收、分布及运输,并观察盐害症状.结果表明：构树幼苗的叶片质膜透性随着NaCl浓度的增加和胁迫时间的延长而升高,根冠比随NaCl浓度的升高而增加,大于3 g·kg^-1的土壤盐胁迫对构树叶片的质膜透性及植株的生物量积累影响显著.构树幼苗各器官中Na⁺和Cl^-含量随土壤NaCl浓度升高而显著增加,K⁺和Ca²⁺则随之降低,叶片各离子含量均明显高于根和茎.说明盐胁迫影响根系对K⁺和Ca²⁺的吸收,并抑制了它们向地上部分的选择性运输,使叶和茎的K⁺和Ca²⁺含量下降.构树通过吸收积累Na⁺和Cl^-抵御土壤盐分带来的渗透胁迫,但过量的Na⁺和Cl^-积累会造成单盐毒害.作为抗盐性较高的非盐生植物,构树地上部分的拒盐作用不显著.     

根系盐胁迫对盐生植物和甜土植物的幼苗生长及矿质元素分布的影响

为了解盐胁迫对植物的影响, 研究了根系NaCl 胁迫在温室条件下对盐生植物榄仁(Terminalia catappa)和甜土植物枇杷(Eriobotrya japonica)幼苗生长、矿质元素和灰分含量的影响。结果表明:在根系盐胁迫下, 两种植物幼苗的叶片病斑多分布于中心区, 灰分含量增加, 幼苗的Na⁺-Cl^- 呈极显著的正相关关系, 盐胁迫对两种植物幼苗的5 种矿质元素(Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^-)含量影响不大, 但它们在植物中的分布发生了变化。可见, 盐生植物和甜土植物抗盐性的区别是量上的不同, 没有质的差别。     

多细胞盐腺离子选择性分泌机理及其成因

为揭示多细胞盐腺对阳离子的选择性分泌机理, 在室内水培条件下, 研究了不同盐分胁迫(NaCl, KCl和NaCl+KCl)对多枝柽柳和短穗柽柳Na⁺, K⁺的分泌和累积, 以及不同盐腺抑制剂(orthovanadate, Ba²⁺, ouabain, tetraethylammonium[TEA]和verapami)对Na⁺和K⁺分泌的抑制及其在体内累积的影响. 结果表明, NaCl处理明显增加了盐腺对Na⁺分泌, 而KCl处理则显著促进K⁺分泌; Na⁺和K⁺的分泌量同累积量的比值表明, Na⁺的比值高于K⁺; 单一盐溶液中添加不同离子成分后, Na⁺和K⁺分泌表现不同: KCl处理中添加NaCl后, K⁺分泌速率显著降低, 但在NaCl处理中添加KCl, Na⁺的分泌则不受影响, 这些结果表明, 柽柳对Na⁺的分泌具有较高的选择性. 此外, 添加盐腺抑制剂后, 柽柳对Na⁺分泌分别受orthovanadate, ouabain, tetraethylammonium[TEA]和verapami的显著抑制, 而K⁺的分泌则分别受ouabain, tetraethylammonium[TEA]和verapami的显著抑制. orthovanadate对Na⁺, K⁺分泌抑制效应的差异, 可能是引起多细胞盐腺分泌Na⁺和K⁺能力不同的主要原因.     

外源H2O2对盐胁迫下小白菜种子萌发和幼苗生理特性的影响

以小白菜"甜脆青"为试材,研究不同浓度（5、10、25、50和100 mmol/L）过氧化氢（H₂O₂）浸种处理对100 mmol/L NaCl胁迫下小白菜（Brassica chinensis L.）种子萌发、幼苗生长及生理特性的影响。结果表明：100 mmol/L NaCl胁迫明显抑制小白菜种子的萌发状况和幼苗生长,发芽势、发芽指数、活力指数及幼苗根和芽长度和鲜重均明显降低,根和芽中CAT的活性及K⁺含量明显受到抑制,渗透调节物质、活性氧和MDA含量显著增加。不同浓度H₂O₂浸种处理提高了NaCl胁迫下小白菜种子发芽势、发芽指数和活力指数,促进小白菜根和芽的生长,增强了NaCl胁迫下根和芽中SOD、CAT和APX的活性及K⁺含量,降低O₂^-·产生速率及H₂O₂和MDA含量,进一步促进脯氨酸和可溶性糖含量的增加,降低体内Na⁺含量。其中以10 mmol/L H₂O₂处理缓解盐胁迫效果最好,明显缓解NaCl胁迫对小白菜种子萌发和幼苗生长的抑制。     

盐地碱蓬二型性种子及其幼苗对盐渍环境的适应性

研究了盐地碱蓬二型性种子中离子含量与刚萌发幼苗耐盐性之间的关系,以及盐分对砂培盐地碱蓬二型性种子的幼苗生长、离子含量及光合特性的影响.棕色种子中离子含量显著高于黑色种子.与对照相比,100和400 mmol/L NaCl对棕色种子幼苗伸长没有抑制作用,却显著抑制黑色种子幼苗的伸长.NaCl处理下棕色种子的幼苗地上部分干重和主茎一级分枝数比黑色种子幼苗高,但二型性种子的幼苗叶片中离子含量、叶绿素含量及光合放氧速率却没有明显差异.上述结果说明盐地碱蓬棕色种子较高的离子含量可能是棕色种子刚萌发幼苗耐盐性较强的重要原因.棕色种子幼苗较高的生物量可能与其较多的分枝数有关.二型种子的这些特征可能决定了其在群落建成中所起到的不同作用.     

不同生境盐地碱蓬对氮饥饿的响应

为了探讨不同生境盐地碱蓬对低氮生境的适应机制,测定了盐渍环境下(200 mmol/L Na Cl)不同浓度硝态氮(0.3、5 mmol/L NO~-_3-N)预处理两种生境盐地碱蓬经氮饥饿后的NO~-_3含量、硝酸还原酶(NR)活性、光合特性及生长状况。结果表明,0.3和5 mmol/L NO~-_3-N处理以及进行氮饥饿时,潮间带生境盐地碱蓬叶片NO~-_3含量均高于内陆生境盐地碱蓬。与内陆生境盐地碱蓬相比,氮饥饿后,潮间带生境盐地碱蓬叶绿素含量、NR活性和光合放氧速率下降幅度均小于内陆生境盐地碱蓬,在0.3mmol/L NO~-_3-N预处理进行氮饥饿时趋势更加明显。0.3 mmol/L NO~-_3-N预处理后氮饥饿对潮间带生境盐地碱蓬根冠比没有影响,却降低内陆生境盐地碱蓬根冠比。上述结果表明,低氮条件下潮间带生境盐地碱蓬具有较高的NO~-_3储存能力,在环境持续氮素缺乏时具有较高的NO~-_3-N再利用能力,能更好地维持氮代谢以及光合性能。说明潮间带生境盐地碱蓬能更好地适应低氮生境。     

Effects of salinity and nitrate on production and germination of dimorphic seeds applied both through the mother plant and exogenously during germination in Suaeda salsa

Salinity and nitrogen are two important environmental factors that affect the distribution of halophytes in their natural saline habitats. Seeds of the euhalophyte Suaeda salsa L. were harvested from plants that had been treated with 1 or 500 mm NaCl combined with 0.5 or 5 mm NO₃^?‐N (nitrate) for 115 days in a glasshouse. Germination was evaluated under different concentrations of NaCl and nitrate. Plants exposed to high salinity (500 mm ) and low nitrate (0.5 mm ) tended to produce heavy seeds. Either high salinity (500 mm ) or high nitrate (5 mm ) increased the brown/black seed ratio. The concentrations of Na⁺, K⁺, and Cl^? were higher in brown than in black seeds, and NO₃^? concentrations were higher in black than in brown seeds, regardless of NaCl and nitrate treatments during plant culture. Regardless of NaCl and nitrate concentrations during germination, seeds from plants grown with 0.5 mm nitrate generally germinated more rapidly than seeds from plants grown with 5 mm nitrate, and the difference was greater for black than for brown seeds. Exogenous nitrate during germination enhanced the germination of brown seeds less than that of black seeds. Producing more brown seeds and heavy black or brown seeds appears to be an adaptation of S. suaeda to saline environments. Producing more black seeds, which tend to remain dormant, should reduce competition for nitrogen and appears to be an adaptation to nitrogen‐limited environments. In conclusion, nitrate provided exogenously or by mother plants to black seeds may act as a signal molecule that enhances the germination of black S. suaeda seeds.     

Ecophysiological responses of the euhalophyte Suaeda salsa to the interactive effects of salinity and nitrate availability

Effects of salinity and nitrate nitrogen (NO₃⁻-N) on ion accumulation and chlorophyll fluorescence were monitored for two populations of Suaeda salsa grown from seeds in a greenhouse experiment. One population inhabits the intertidal zone and the other occurs on inland saline soils. Ion contents in soils and in leaves of the two populations were also investigated in field. In the greenhouse, seedlings were exposed to a NaCl concentration of 0.6 and 35.1 ppt, with 0.1 or 5 mM NO₃⁻-N treatments for 20 days. The contents of Na⁺ and Cl⁻ were higher, but NO₃⁻ was lower in soils of the intertidal zone than at the inland site. In the field, ion concentrations and the estimated contribution of these ions to osmotic potential in leaves showed no difference between the two populations, except that the estimated contribution of Na⁺ to osmotic potential in leaves of the intertidal population was lower than that in the inland population. In the greenhouse, in contrast, the concentration of Cl⁻ was lower, but NO₃⁻ concentration and the estimated contribution of NO₃⁻ to osmotic potential were higher, in the leaves of plants from the intertidal zone. Salinity had no effect on the maximal efficiency of PSII photochemistry (Fv/Fm) and the actual PSII efficiency (ΦPSII). The results indicated that S. salsa from the intertidal zone was better able to regulate Cl⁻ to a lower level, and accumulate NO₃⁻ even with low soil NO₃⁻ concentrations. Tolerance of the PSII machinery to high salinity stress may be an important characteristic for the studied species supporting growth in highly saline environments.     

Differential salt tolerance and similar responses to nitrogen availability in plants grown from dimorphic seeds of Suaeda salsa

Suaeda salsa is an annual halophyte which produces two morphologically distinct types of seeds on the same plant. The main purpose of this study was to investigate growth responses of S. salsa plants to different levels of NaCl and nitrate nitrogen, and its significance from the viewpoint of photosynthetic physiology. In a pot experiment, we sowed seeds belonging to the two morphs into a substrate with three salinity and three nutrient levels. Plants derived from brown seeds grew well at moderate salinity (300 mmol L⁻¹ NaCl). Shoot weight of plants from black seeds gradually decreased with the increase of salinity. Plants derived from both seed morphs had the same growth rates under similar nitrogen levels. Plant growth status was generally related to chlorophyll content and photosynthetic rates. Our study shows that plants grown from the two different seed morphs of S. salsa exhibit different salt tolerance, but have similar responses to nitrate nitrogen. This is the first report on different responses to salinity and nitrogen availability in plants with heteromorphic seeds.     

Effect of salinity on germination,seedling emergence,seedling growth and ion accumulation of a euhalophyte Suaeda salsa in an intertidal zone and on saline inland

The effect of salinity on germination, seedling emergence, seedling growth and ion accumulation of a euhalophyte Suaeda salsa L. in an intertidal zone and on saline inland were investigated. Brown seeds of S. salsa were heavier and better developed than black seeds in both the intertidal zone and on saline inland. The brown seeds/black seeds ratio for S. salsa in the intertidal zone was much higher than that for S. salsa on saline inland. More germinated seeds grew as seedlings under high salinity for S. salsa from the intertidal zone than S. salsa on saline inland; high salinity decreased the shoot length more severely for S. salsa from saline inland than for S. salsa from the intertidal zone; the seedling growth at a range of NaCl, measured either as shoot length or shoot dry weight, for S. salsa from the intertidal zone was lower than that of S. salsa from saline inland. In conclusion, for S. salsa from the intertidal zone there appears to be selection for slower growth and producing more brown seeds. The establishment of populations of S. salsa in different saline environments depends on the responses of seed germination, seedling emergence and seedling growth to salinity. These characteristics may determine the natural distributions of S. salsa populations in different saline environments.     

Effect of salinity on growth, ion accumulation and the roles of ions in osmotic adjustment of two populations of Suaeda salsa

The effect of salinity on growth, ion accumulation and the roles of ions in osmotic adjustment of two populations of Suaeda salsa were investigated. Seeds were collected from an intertidal zone or a saline inland zone in the Yellow River Delta in Shandong province, China. Seedlings were exposed to 10, 100, 200, 400 or 600 mM NaCl for 18 days in a greenhouse. NO₃ ^? concentration in the soil where S. salsa grows in an intertidal zone was much lower than that for the second population, but leaf NO₃ ^? concentration was the same in the two populations under field conditions. When plants were cultured in a greenhouse under natural light conditions, S. salsa from the intertidal zone showed fewer main stem branches and lower relative shoot growth compared to S. salsa from saline inland. Leaf Cl^? concentration of saline inland S. salsa was significantly higher than that of S. salsa from the intertidal zone, while the opposite was true for the concentration of NO₃ ^? in leaves of plants. For S. salsa from the intertidal zone NO₃ ^? contributed more than Cl^? to the osmotic potential, whereas S. salsa from the saline inland exhibited a reverse relationship under saline conditions, indicating that NO₃ ^? plays an important osmotic role in S. salsa from the intertidal zone in high salinity. In conclusion, S. salsa from the intertidal zone may employ superior control of ion uptake and content than S. salsa from the saline inland zone. The two populations of Suaeda salsa presented different ability in chloride exclusion and nitrate accumulation. These characteristics may affect the distributions of S. salsa in natural highly saline environments.     

Accumulation of ions during seed development under controlled saline conditions of two Suaeda salsa populations is related to their adaptation to saline environments

Controlled conditions were used to investigate the relationship between ion distribution in developing seeds of two Suaeda salsa populations and seed germination and seedling emergence. Seeds were harvested from S. salsa plants that had been treated with 1 or 400 mM NaCl for 122 (saline inland population) or 135 days (intertidal zone population) in a glasshouse. Germination and seedling emergence were evaluated under salinity. In both populations, more ions were accumulated in the pericarps of plants cultured in 400 mM NaCl than in 1 mM NaCl. Pericarps accumulated much higher ion concentrations in the intertidal zone population than in the saline inland population, while the opposite trend occurred for ion accumulation in the embryos. Seeds of plants from the intertidal zone population germinated more rapidly than those from plants of the saline inland population, regardless of the NaCl concentration during seed germination. However, seedling emergence under high salinity was lower with seeds from the intertidal zone population than with seeds from the saline inland population. In conclusion, S. salsa in the intertidal zone employs superior control of ion compartmentalization in the pericarps to tolerate salinity but requires a minimal level of ions in embryos to ensure seedling establishment in highly saline environments. This indicates that euhalophytes require salts during the mature seed stage to maintain seed viability and to ensure seedling emergence and population establishment.     

Ecophysiological responses of the euhalophyte Suaeda salsa to the interactive effects of salinity and nitrate availability

Effects of salinity and nitrate nitrogen (NO₃⁻-N) on ion accumulation and chlorophyll fluorescence were monitored for two populations of Suaeda salsa grown from seeds in a greenhouse experiment. One population inhabits the intertidal zone and the other occurs on inland saline soils. Ion contents in soils and in leaves of the two populations were also investigated in field. In the greenhouse, seedlings were exposed to a NaCl concentration of 0.6 and 35.1 ppt, with 0.1 or 5 mM NO₃⁻-N treatments for 20 days. The contents of Na⁺ and Cl⁻ were higher, but NO₃⁻ was lower in soils of the intertidal zone than at the inland site. In the field, ion concentrations and the estimated contribution of these ions to osmotic potential in leaves showed no difference between the two populations, except that the estimated contribution of Na⁺ to osmotic potential in leaves of the intertidal population was lower than that in the inland population. In the greenhouse, in contrast, the concentration of Cl⁻ was lower, but NO₃⁻ concentration and the estimated contribution of NO₃⁻ to osmotic potential were higher, in the leaves of plants from the intertidal zone. Salinity had no effect on the maximal efficiency of PSII photochemistry (Fv/Fm) and the actual PSII efficiency (ΦPSII). The results indicated that S. salsa from the intertidal zone was better able to regulate Cl⁻ to a lower level, and accumulate NO₃⁻ even with low soil NO₃⁻ concentrations. Tolerance of the PSII machinery to high salinity stress may be an important characteristic for the studied species supporting growth in highly saline environments.     

不同氮处理下速生柳对水体氮的吸收、分配及生理响应

采用水培法,研究了旱柳苗在外源添加不同氮水平(贫氮、中氮、富氮、过氮)的铵态氮(NH+4-N)和硝态氮(NO-3-N)的生长、氮吸收、分配和生理响应。结果表明:一定范围氮浓度的增加能够促进旱柳苗的生长,但过量氮会抑制其生长,且NH+4-N的抑制作用大于NO-3-N;两种氮处理下,旱柳表现出对NH+4-N的吸收偏好,在同一氮水平时,旱柳各部位氮原子百分含量Atom%15N(AT%)、15N吸收量和来自氮源的N%(Ndff%)均为NH+4-N处理大于NO-3-N处理,且随着氮浓度的增加,差异增大,且在旱柳各部位的分布为根﹥茎﹥叶;2种氮素过量和不足均会对旱柳根和叶生理指标产生不同的影响,其中在过氮水平时,NH+4-N和NO-3-N处理下根系活力比对照减少了50.61%和增加了19.53%;在过氮水平时,NH+4-N处理柳树苗根总长、根表面积、根平均直径、根体积和侧根数分别对照下降了30.92%、29.48%、19.44%、27.01%和36.41%,NO-3-N处理柳树苗相应的根系形态指标分别对对照下降了1.66%、5.65%、1.49%、5.06%和25.72%。可见,高浓度NH+4-N对旱柳苗的胁迫影响大于NO-3-N,在应用于水体氮污染修复时可通过改变水体无机氮的比例,削弱其对旱柳的影响,从而提高旱柳对水体氮污染的修复效果。