盐胁迫对不同生境盐地碱蓬光合及离子积累的影响

为了探讨盐地碱蓬(Suaeda salsa)适应不同生境的生理机制, 研究了盐处理(1、200和600 mmol·L^-1 NaCl)对盐碱地和潮间带两种生境盐地碱蓬地上部分及根系有机干重、叶片叶绿素含量及光合放氧速率、叶片和根中离子积累的影响。结果表明: 200 mmol·L^-1 NaCl对两种生境盐地碱蓬地上部分及根系的有机干重无显著影响, 说明两种生境盐地碱蓬均具有较强的抗盐性; NaCl处理显著降低了两种生境盐地碱蓬叶片的光合放氧速率; 各浓度NaCl处理下, 盐碱地生境盐地碱蓬叶片的光合放氧速率均高于潮间带生境的, 潮间带生境盐地碱蓬叶片中叶绿素a与叶绿素b的比值均高于盐碱地生境的; 各浓度NaCl处理下, 潮间带生境盐地碱蓬叶片中的Cl^-含量均低于盐碱地生境的; 与叶片中情况相反, 高盐处理下, 潮间带生境盐地碱蓬根中的Cl^-含量均高于盐碱地生境的。说明与盐碱地生境盐地碱蓬相比, 潮间带生境盐地碱蓬的根系可能对Cl^-具有较强的积累或限制其向地上部分运输的能力, 这些特征可能是盐地碱蓬适应不同生境的结果。     

8种盐生植物种子萌发特征与NaCl盐度的关系

耐盐植物的选育是盐渍土地生物改良的关键。通过对13个NaCl盐度梯度下,真盐生植物囊果碱蓬、盐地碱蓬、高碱蓬、盐角草、盐爪爪,泌盐植物大叶补血草、耳叶补血草、黄花补血草8种盐生植物的萌发试验,测定其种子发芽率、发芽势、发芽指数和相对盐害率等指标,研究不同NaCl盐度胁迫对其萌发特性的影响。结果表明：低盐度（50 mmol/L）能促进8种盐生植物的萌发;随着盐度的上升,盐角草、盐地碱蓬、囊果碱蓬、高碱蓬表现出较强的萌发耐盐性,发芽势和发芽指数优于其他植物;盐角草的萌发耐盐性最佳,在1000 mmol/L盐度下萌发率仍能达到54.0%。进一步通过S型生长曲线和线性模型分析得出,8种植物为对抗逆境大致分为"快速型"和"缓慢型"两种萌发策略;随盐度的升高,初始萌发时间和萌发高峰时间均不同程度的向后推迟。盐度≤200 mmol/L时,囊果碱蓬的萌发占据优势,其萌发速率大于其他植物,且差异显著;中盐度400 mmol/L左右时,盐地碱蓬和盐角草萌发最快,二者无显著差异;盐度≥600 mmol/L时,盐角草萌发速率较快,相比其他植物差异显著。泌盐植物的萌发耐盐适宜浓度和耐盐极限浓度均低于真盐生植物。8种植物均有作为氯化物为主盐渍土地区生物改良材料的潜力。     

真盐生植物囊果碱蓬(Suaeda physophora)脱水种子子叶叶绿素特征及其对植物萌发阶段适应盐渍环境的生态意义

本研究观察到囊果碱蓬(Suaeda physophora)脱水种子子叶含有深绿色色素, 分别在645和663 nm波长下测定了脱水种子子叶和黑暗中在去离子水半浸没12 h的种子子叶内色素含量及其在400~700 nm波长范围内的光谱吸收特征曲线, 并与囊果碱蓬真叶内的叶绿素光吸收特征曲线进行比较, 结果显示这种色素是叶绿素, 其光吸收特征曲线与真叶叶绿素的几乎完全相同, 表明这种叶绿素具有和真叶叶绿素相近的生理功能. 通过光合能力测定发现, 囊果碱蓬脱水种子吸水6 h后就能进行光合放氧. 用电子显微镜观测了在去离子水和700 mmol/L NaCl溶液中处理1天和10天的囊果碱蓬种子的叶绿体形态, 同时对胚根细胞质膜的受损伤程度进行了组织化学染色观测, 并以同为黎科、且脱水种子子叶中也存在叶绿体的旱生植物白梭梭(Haloxylon persicum)为对照进行同步观测. 结果表明, 相对于非盐生植物白梭梭, 高盐度下囊果碱蓬种子的子叶叶绿体结构、胚根细胞质膜均保持完好, 表现出很强的抗盐能力. 黑暗条件下囊果碱蓬种子在去离子水和700 mmol/L NaCl溶液中的萌发过程是渐进式的, 72~84 h才能达到萌发高峰; 但是在700 mmol/L NaCl溶液中浸泡10天而未萌发的种子移到去离子水中以后的恢复萌发则是爆发式的, 在24 h之内即达到萌发高峰, 并且这些种子具有光合能力. 因此可以推断, 高浓度的盐分对于真盐生植物囊果碱蓬的快速恢复萌发具有激发效应, 这种特性保证了种子在自然条件下能够在早春短暂的、适宜的土壤低盐分条件下迅速萌发; 干燥种子子叶中保留的具有完整结构的叶绿体则可通过光合作用保证萌发了的幼苗迅速生长, 建立种群.     

NaCl胁迫对2种表型盐地碱蓬种子萌发的渗透效应和离子效应研究

采用高低2个浓度的NaCl、LiCl及等渗甘露醇溶液处理紫红色表型(紫色型)和绿色表型(绿色型)盐地碱蓬种子,通过测定它们的种子萌发率、吸胀速率和胚内离子含量,研究NaCl胁迫对2种表型种子萌发的离子效应和渗透效应.结果表明:(1)2种表型盐地碱蓬种子萌发率在高浓度(300 mmol/L)和低浓度(100 mmol/L)NaCl处理下均显著降低,紫色型种子萌发率在低浓度下显著低于绿色型,而在高浓度下却显著高于绿色型;绿色型种子萌发率在高浓度(30 mmol/L)和低浓度(10 mmol/L)LiCl处理下均未受到显著影响,但紫色型种子萌发率却均极显著降低;2种表型盐地碱蓬种子萌发率在低浓度等渗甘露醇处理下均极显著低于低浓度NaCl处理,而高浓度等渗甘露醇处理却均与高浓度NaCl处理无显著差异.(2)2表型种盐地碱蓬种子的吸胀速率在低浓度NaCl处理下没有受到显著影响,但高浓度NaCl处理及与之等渗的高浓度甘露醇处理下都显著降低,而且紫色型种子的吸胀速率在等渗甘露醇处理时显著高于绿色型.(3)2种表型盐地碱蓬种子胚中的Na 含量和Na /K 在对照和低浓度NaCl处理下无显著差异,但紫色型种子胚中的Na 、K 含量在高浓度NaCl处理时都显著高于对照,且K 含量增加的幅度远大于Na 含量,导致紫色型种子胚中的Na /K 显著低于绿色型.研究发现,盐地碱蓬种子萌发在低浓度NaCl胁迫下主要受离子效应抑制,而高浓度NaCl胁迫下则主要受渗透效应抑制,紫色型种子萌发率在高浓度NaCl胁迫下高于绿色型的原因之一是前者能维持更低的Na /K 比.     

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。     

KCl和NaCl处理对盐生植物碱蓬幼苗生长和水分代谢的影响

研究了用不同浓度KCl和等浓度NaCl处理的盐生植物碱蓬幼苗水分代谢的变化.结果表明,NaCl处理显著促进碱蓬生长,根吸水增加,含水量高于对照.而相同浓度KCl处理却严重抑制碱蓬生长,含水量显著下降,400 mmol/L的 KCl处理后6 d,地上部分发生萎蔫,尔后死亡.KCl处理伤害碱蓬的原因之一是抑制根系吸水,而对蒸腾速率无显著影响,即水分吸收速率与蒸腾速率比值下降,植株缺水引起伤害.     

NaCl胁迫对3种荒漠植物幼苗叶绿素荧光参数的影响

以生长在荒漠地区的典型盐生植物囊果碱蓬(Suaeda physophora Pall.)、旱生植物梭梭[Haloxylon am-modendron(C.A.Mey.)Bunge]和超旱生植物白梭梭(Haloxylon persicum Bunge ex Boiss.et Buhsee)的幼苗为实验材料,研究了它们在不同NaCl浓度处理下的叶绿素荧光参数变化特征.结果表明:在NaCI胁迫下,同期囊果碱蓬的PSⅡ潜在活性(Fv/Fo)和最大光化学量子产量(Fv/Fm)降低幅度较小,而梭梭和白梭梭则有较明显降低,而且囊果碱蓬显著高于后两者;同期光合量子产量(Yield)和表观光合电子传递速率(ETR)均以囊果碱蓬最大并显著高于其余2种植物,而梭梭与白梭梭之间无显著差异.囊果碱蓬和梭梭的Yield和ETR并不随NaCl浓度的增加而降低;同一植物的荧光参数在各浓度盐处理间无显著差异.在本实验条件下,NaCl胁迫并未使囊果碱蓬的PSⅡ受到明显损伤,其仍能够较正常地吸收光能进行光合作用,对盐分胁迫有较强的忍耐能力;适度的盐渍对囊果碱蓬和梭梭幼苗的生长是有益的;盐胁迫效应主要表现为种间差异,而非处理间差异;叶绿素荧光技术可以有效应用于耐盐植物筛选.     

钠盐和氯化物对真盐生植物盐地碱蓬营养生长的影响

200mmol·L~(-1)NaCl显著促进真盐生植物盐地碱蓬(Suaeda salsa)的营养生长,但具体是Na~+、Cl~-还是二者共同起作用尚不清楚。本文分别采用0、200mmol·L~(-1)NaCl以及相同浓度的钠盐(由NaNO_3、NaH_2PO_4、Na_2SO_4组成)、氯化物(由MgCl_2、KCl、CaCl_2、NH_4Cl组成)自种子播种开始处理盐地碱蓬,对植株的生物量、离子含量、光合和荧光等营养生长相关参数进行研究,结果表明:200mmol·L~(-1)NaCl和钠盐处理显著增加盐地碱蓬的株高、分枝数、干鲜重等,其中200mmol·L~(-1)钠盐处理的促进作用最显著;而200mmol·L~(-1)氯化物处理显著抑制了盐地碱蓬的营养生长,植物矮小,黄化严重。进一步研究发现NaCl和钠盐处理显著增加了盐地碱蓬叶片中叶绿素含量,提高了植株净光合速率;而同浓度氯化物处理降低了盐地碱蓬叶片中叶绿素含量,其净光合速率显著下降。以上结果表明:Na~+通过促进光合作用促进稀盐型盐生植物盐地碱蓬的营养生长,而Cl~-有抑制作用。     

NaCl对中华补血草叶片盐腺发育及其泌盐速率的影响

以中华补血草(Limonium sinenseKuntze)为实验材料,研究了不同浓度NaCl处理对其生长、盐腺发育及泌盐速率的影响.结果显示:(1)随着NaCl浓度的升高,植株干重和鲜重均先显著升高后逐渐下降,当NaCl处理浓度为100 mmol/L时,植株干、鲜重达到最大;(2)与对照相比,300 mmol/L NaCl处理下盐腺的分泌细胞及平均直径差异不显著,而在1002、00 mmol/L的NaCl处理下显著增大;(3)随着NaCl浓度的升高,盐腺密度显著升高且叶片上表面盐腺总数明显高于对照,单个盐腺的泌盐速率和叶片整体泌盐速率均显著升高.结果表明,100~200 mmol/L NaCl处理可显著促进中华补血草盐腺的发育及泌盐能力,300 mmol/L以上NaCl处理对盐腺的直径影响不显著,但可显著促进盐腺的泌盐能力.     

真盐生植物盐角草对不同氮形态的响应

盐角草(Salicornia europaea L.)是一种喜盐植物,其最佳生长的实现需要200—400 mmol/L NaCl。为了解盐渍环境下盐角草氮素吸收利用特点,在水培添加200或400 mmol/L NaCl情况下,从生长指标,光合参数,根系体积和活力,硝酸还原酶与谷氨酰胺合成酶活力,蛋白、总氮、硝态氮及铵态氮含量等方面检测了硝态氮、铵态氮和尿素3种氮形态对盐角草生长的影响。研究发现以氮摩尔浓度(mmol/L)计,在0.1—400 mmol/L浓度范围进行测试,盐角草在0.1 mmol/L低氮条件下仍能维持生长,同时,抑制盐角草生长的氮浓度域值较高,其中铵态氮、尿素和硝态氮分别为50、50及400 mmol/L。研究结果表明盐角草吸收利用氮素的能力强,对氮素的浓度耐受范围宽,3种氮形态都可作为氮源满足其生长需要,但有效促进生长的效果存在差异,总体顺序从高到低依次为硝态氮、铵态氮和尿素。研究为揭示盐生植物氮吸收利用特点提供了基础数据,对提高盐生植物生产力,指导沿海滩涂生态建设具有一定的指导意义。     

盐胁迫对柳枝稷苗期生长和生理特性的影响

2010年,在人工气候室中设置了0、50、100、150和200 mmol·L-15种NaCl浓度处理,分析盐胁迫对柳枝稷苗期生长的影响.结果表明:随着NaCl浓度的增加,柳枝稷的生长明显受到抑制,株高降低、叶片变小、光合叶面积减少、净光合速率下降,干物质积累量显著降低,表现出甜土植物的特点.柳枝稷的耐盐能力较强,在200 mmol·L-1NaCl溶液中处理30 d后仍能存活,单株绿叶面积为491.9 cm2,净光合速率为0.93 μmol CO2·m-2·s-1.本试验条件下,以生长量下降50％为标准求得柳枝稷的耐盐阈值为178.6 mmol·L-1.     

外源水杨酸对盐胁迫下大黄种子萌发及幼苗生长的影响

该研究以掌叶大黄、唐古特大黄和药用大黄种子为材料,采用双层滤纸培养法,设置系列浓度NaCl (0、100、150、200、250 mmol/L) 胁迫试验,以及系列浓度水杨酸(SA)溶液(0、50、100、150、200、250 mg/L)拌种和浸种后盐胁迫实验,测定3种大黄种子萌发及幼苗生长指标,揭示外源水杨酸对盐胁迫下大黄种子萌发及幼苗生长的影响。结果显示：(1)随NaCl浓度增大3种大黄种子的发芽率均呈直线下降趋势,且子叶、胚轴、根和苗等生长均受到强烈抑制。(2)在拌种条件下, 200 mmol/L NaCl胁迫下掌叶大黄苗长在200 mg/L SA处理下受到显著促进; 200 mmol/L NaCl浓度盐胁迫下唐古特大黄种子发芽率在250 mg/L SA处理下受到显著抑制;100 mmol/L NaCl胁迫下药用大黄种子发芽势在200 mg/L SA处理下受到显著抑制,其发芽率在150 mg/L SA处理下得到显著抑制,其苗长在250 mg/L SA处理下受到显著抑制。(3)在浸种条件下, 200 mmol/L NaCl胁迫下掌叶大黄种子发芽率在50 mg/L SA处理下显著提高,其幼苗根长和苗长的生长在250 mg/L SA处理受到显著促进;200 mmol/L NaCl胁迫下唐古特大黄种子的发芽势在200 mg/L SA处理下得到显著促进,其幼苗根和苗的生长在50 mg/L SA处理下得到显著促进;100 mmol/L NaCl 胁迫下药用大黄根和苗的生长在100 mg/L SA处理下均得到显著促进。研究表明,3种大黄种子和幼苗对盐胁迫的响应趋势一致,但对不同浓度SA拌种和浸种的响应有较大差异。     

NaCl胁迫对海蓬子(Salicornia bigelovii Torr.)离子区室化、光合作用和生长的影响

用含有0、100、300、600mmol/L的NaCl的Hoagland培养液处理海蓬子幼苗,处理一定时间后测定其鲜重、干重、离子含量、Na /K 比值、Na 在细胞中的分布、光合速率、叶绿体超微结构等的变化.结果表明一定浓度NaCl处理促进了海蓬子的生长,300mmol/L左右的NaCl是海蓬子生长的最适盐度.盐处理条件下海蓬子主要将Na 、Cl-积累在地上部,且主要储存在液泡中.随盐处理浓度的增加海蓬子地上部的Na /K 比增大;光合速率在低盐度下随盐浓度的升高而增大,高盐度下受到抑制;叶绿体超微结构在高盐度下受到部分破坏.     

Effect of salinity on seed germination,ion content and photosynthesis of cotyledons in halophytes or xerophyte growing in Central Asia

Aims We investigated the impact of salinity on seed germination, chlorophyll content, chloroplast structure and photosynthesis of the green embryos in desiccated seeds of the xerophyte Haloxylon persicum, xero-halophyte Haloxylon ammodendron and euhalophyte Suaeda physophora.Methods Seeds of H. persicum, H. ammodendron and S. physophora were collected from natural environment in Fukang, Xinjiang province. Pretreatment with 700 mM NaCl was carried out to stimulate the natural 'seed priming'; we analyzed the joint effect of salinity and different species on germination physiology and cotyledonal structure and photosynthetic function changes during germination and recovery stage.Important findings We found that seeds did not suffer ion toxicity for the two halophytes H. ammodendron and S. physophora, as evidenced by the high final germination after ungerminated seeds pretreated with 700 mM NaCl were transferred to distilled water, but the final germination of the xerophyte H. persicum was significantly lower than that of control. The Na + concentration in embryos increased under salinity for all species, while K + concentration decreased by salinity only for H. persicum and H. ammodendron, i.e. the concentration of K + in embryos of H. persicum and H. ammodendron decreased by 36% and 46%, respectively. For all species, whether dry intact seeds or cotyledons of dry seeds imbibed in deionized water and NaCl solution, had high chlorophyll content. Treatment with NaCl also caused chloroplast thylakoids to swell and chlorophyll content to decrease in seeds of H. persicum, but no significant change was observed in the more salt-tolerant species S. physophora and H. ammodendron. Fluorescence measurement showed that 700 mM NaCl decreased the Fv/Fm ratio of cotyledons in seeds for all species, especially for H. persicum and H. ammodendron. Photosynthetic oxygen releasing was detected from the seeds that were moistened with distilled water and 700 mM NaCl for 6 or 24 h and from the seeds that were initially moistened with 700 mM NaCl in darkness for 10 days, then transferred to distilled water for another 6 and 24 h. The results indicated that the chlorophyll in cotyledon of desiccated seed had photosynthetic function in early germination stage, even under high-saline condition. In addition, the photosynthesis of chlorophyll in the embryonic cotyledons of desiccated seeds during germination was similar to that in leaves of young seedlings for all species. In conclusion, the chloroplasts of the two halophytes were more salt resistant compared with the xerophyte H. persicum. The photosynthetic function of chlorophyll in cotyledons of mature seeds may be ecologically important for seedling development in early stage for plants growing in extremely saline or arid environments.     

Isolation and characterization of salinity resistant mutant of a nitrogen-fixing cyanobacterium, Anabaena doliolum

D.V. SINGH. A.K. TRIPATHI AND H.D. KUMAR. 1991. Sodium chloride, up to 20 mmol/l concentration, had a positive effect on acetylene reducing activity and photosynthetic oxygen evolution of a paddy field cyanobacterium, Anabaena doliolum. Beyond 20 mmol/l level of salinity adverse effects appeared. A mutant resistant to 200 mmol/l NaCl was isolated by nitrosoguanidine mutagenesis. The mutant, NaCl-R₂₀₀, showed about 20–25% more nitrogenase activity and photosynthetic oxygen evolution than the parent. Better capacity of nitrogen fixation and photosynthesis possibly could help the mutant in synthesis of osmotic stabilizer to resist the salinity stress.     

Effect of oxygen availability and salinity on EARLY LIFE HISTORY STAGES OF SALT MARSH PLANTS. I. Different germination strategies of Spartina alterniflora and Phragmites australis (Poaceae)

Gradients in oxygen availability and salinity are among the most important environmental parameters influencing zonation in salt marsh communities. The combined effects of oxygen and salinity on the germination of two salt marsh grasses, Spartina alterniflora and Phragmites australis, were studied in growth chamber experiments. Germination of both species was initiated by emergence of the shoot and completed by root emergence. Percentage S. alterniflora germination was reduced at high salinity (40 g NaCl/L) and in decreased oxygen (5 and 2.5%). In 0% oxygen shoots emerged, but roots did not. P. australis germination was reduced at a lower salinity (25 g NaCl/L) than S. alterniflora, and inhibited at 40 g NaCl/L and in anoxia. However, a combination of hypoxia (10 and 5% O2) and moderate salinity (5 and 10 g NaCl/L) increased P. australis germination. When bare areas in the salt marsh are colonized, the different germination responses of these two species to combinations of oxygen and salt concentrations are important in establishing their initial zonation. In high salinity wetlands S. alterniflora populates the lower marsh and P. australis occupies the high marsh at the upland boundary.     

Root morphology is related to the phenotypic variation in waterlogging tolerance of two populations of Suaeda salsa under salinity

The effects of waterlogging and salinity on seedling emergence, seedling growth and ion accumulation in a euhalophyte Suaeda salsa in an intertidal zone and on saline inland soil were investigated. Seedlings of S. salsa from the intertidal zone emerged more rapidly than those of the inland population under both waterlogged and drained conditions. Waterlogging and salinity had no adverse effects on seedling emergence of S. salsa from the intertidal zone, but markedly inhibited this parameter in the inland population. Waterlogging did not affect the seedling survival, shoot dry mass, and shoot height in high salinity in S. salsa from the intertidal zone, while the opposite trend was shown in the inland population. The root dry mass was higher in S. salsa from the intertidal zone as compared to the inland population, in waterlogged treatments by 1.9, 1.3, and 1.5 times in 1, 200, and 600 mM NaCl, respectively, and in drained treatments by 1.8, 2.3, and 3.0 times in 1, 200, and 600 mM NaCl, respectively. Waterlogging increased Na⁺ and K⁺ concentrations in high salinity, but waterlogging had no effect on Cl^- concentration in shoots of S. salsa from the intertidal zone. In all NaCl treatments, waterlogging had no effect on concentrations of these ions in shoots of S. salsa from the saline inland site. In a field investigation, the fresh mass of shoots and roots were lower, whereas the root/shoot ratio was 1.5 times higher in S. salsa from the intertidal zone, compared with the inland population. These findings indicate that S. salsa population from the intertidal zone is more waterlogging tolerant than the inland population. S. salsa from the intertidal zone produced relatively more root biomass and this might help anchor plants against tidal action in the intertidal zone. The physiological and morphological characteristics may determine the natural distributions of the two S. salsa populations in their different saline environments.