Na2CO3胁迫对星星草叶肉细胞超微结构的影响

利用透射电镜技术对Na₂CO₃胁迫下星星草叶肉细胞超微结构进行了观察。结果表明：未胁迫的叶肉细胞排列疏松,各种细胞器结构完整,叶绿体含少量淀粉粒和脂质球。轻度盐胁迫（2g/L,4g/L Na₂CO₃）对叶肉细胞超微结构影响较小。中度盐胁迫（6g/L,8g/L Na₂CO₃）引起叶肉细胞超微结构的变化,叶绿体类囊体肿胀,基粒紊乱,不含淀粉粒,脂质球数量增加,叶绿体由原来的梭形或椭球形变成圆球状;部分线粒体嵴消失,出现晶体结构;中央大液泡破裂;核逐渐降解。高度盐胁迫（10g/L,12g/L Na₂CO₃）下,叶绿体片层结构消失,脂质球数量增加,体积变大,被大量的膜片层所包围,叶绿体内、外膜消失,叶肉细胞中看不到叶绿体的存在;膜片层包围线粒体;叶肉细胞中可见大量的泡状结构和膜片层,叶肉细胞死亡。上述结果表明,细胞器特别是叶绿体膜结构的破坏与盐胁迫叶肉细胞最终死亡密切相关     

四倍体刺槐的抗盐性

 以四倍体刺槐(Robinia pseudoacacia)为主要试验材料,以二倍体刺槐为对照材料,在两种盐胁迫下,对苗木的形态、生理生化、光合特性和解剖结构等指标的变化规律进行了研究。利用NaCl和Na₂SO₄盐溶液对两种刺槐进行盐处理,在30 d后每7 d处理1次,共处理4次,并在处理前和处理后每7 d进行各项指标的测定。结果发现：1)在盐胁迫下二倍体刺槐的植株生长受到强烈抑制,叶片含水量和叶绿素含量显著低于对照,有明显的盐害症状;对四倍体刺槐植株的生长影响较小,叶片含水量和叶绿素含量也与对照差异不显著,无盐害症状。2)四倍体刺槐经过盐处理后相对电导率和脯氨酸(Proline, Pro)含量虽然也稍有上升,但与对照相比未达到显著水平,而二倍体刺槐显著高于对照;同时作为保护酶系统的过氧化物酶(Peroxidase, POD)、超氧化物歧化酶(Superoxide dismutase, SOD)、过氧化氢酶(Catalase, CAT)在四倍体刺槐经盐胁迫后期也保持了较高的活性,从而提高了其抗盐性,而对盐敏感的二倍体刺槐3个保护酶活性均较低。 3)经盐胁迫后对四倍体刺槐光合特性影响不大,净光合速率（Net photosynthetic rate, P_n）和胞间CO₂浓度（Intercellular CO₂ concentration, C_i）均无显著变化,而二倍体刺槐P_n和C_i显著下降。4)经盐胁迫后四倍体刺槐在解剖结构上做出了积极的反应：叶肉栅栏组织拉长、排列更为紧密、 海绵组织变小、排列紧密。而二倍体刺槐出现了相反的现象。综合以上分析认为：四倍体刺槐具有较强的抗盐性。     

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。     

广州大夫山雨季林内外空气TSP和PM2.5浓度及水溶性离子特征

采用平行同步采样法,于2012年雨季,对广州市大夫山森林公园林内外空气的总悬浮颗粒物(TSP)和细颗粒物(PM_2.5)样品进行了24 h收集,测定了TSP和PM_2.5的质量浓度并分析了样品中水溶性无机离子成分。结果表明:林内外PM_2.5的质量浓度平均值分别为(40.18±10.47)和(55.79±13.01) g/cm³;林内外TSP的质量浓度分别为(101.32 ± 33.19)和(116.61±35.36) g/cm³。林内与林外比,PM_2.5和TSP平均质量浓度都显著减少(P < 0.05),表明森林能显著改善空气环境质量。TSP和PM_2.5中SO₄^2-、Na⁺、NH₄⁺和NO₃^-为水溶性无机离子主要成分,占总离子质量的80%以上,林外这些离子的浓度高于林内(NH₄⁺除外)。这4种离子雨季在空气中的主要存在方式为NaCl、Na₂SO₄、NH₄HSO₄和NH₄NO₃。计算表明,采样期间海盐对大夫山空气TSP和PM_2.5的水溶性组分中Na⁺和Cl^-贡献最大,其它元素主要源自陆地源。林内外TSP和PM_2.5的c(NO₃^-)/c(SO₄^2-)比值在0.3以下,表明固定源是大夫山森林公园空气主要污染贡献者,TSP中c(NO₃^-)/c(SO₄^2-)的比值大于PM_2.5的比值,说明移动源对TSP的贡献大于PM_2.5。     

盐胁迫对玉米叶片叶肉细胞生物膜超微结构的影响

研究了NaCl胁迫对玉米叶肉细胞生物膜超微结构的影响. 结果表明：NaCl胁迫破坏了玉米叶片叶肉细胞生物膜的正常结构,50 mmol·L^-1 NaCl处理胁迫下,玉米叶肉细胞核膜,线粒体膜,细胞膜,叶绿体膜,液泡膜都受到不同程度的破坏,叶绿体基粒类囊体膨胀,间质片层空间增大,片层紊乱。100 mmol·L^-1 NaCl处理胁迫下,质膜,液泡膜,线粒体,叶绿体都受到严重的破坏。细胞质膜破坏,破损的叶绿体充斥在细胞间隙中;叶绿体外膜破坏,甚至解体消失,叶肉细胞中充满膜结构,基粒排列方向改变,垛叠层数减少,基粒和基质片层界限模糊不清,有的基粒解体消失,甚至叶绿体完全解体;核膜破坏、解体,核中的染色质高度凝缩;线粒体的数量增多,线粒体膜破坏,脊的数量减少,甚至整个线粒体破损解体;液泡膜破坏;由于各种生物膜的破坏,使细胞内充满许多囊状小泡、多泡体或斑层小体;叶肉细胞发生严重的质壁分离,严重时发生细胞壁断裂;甚至整个细胞溶解。     

外源CaCl2对NaCl胁迫下酸枣幼苗氮代谢的影响

为了研究CaCl₂对NaCl胁迫下酸枣幼苗根、茎、叶的氮代谢影响,探索钙缓解幼苗NaCl胁迫的作用途径。该研究以酸枣幼苗为试验材料,检测不同浓度CaCl₂(0、5、10、20 mmol/L)对NaCl(150 mmol/L)胁迫下幼苗叶片H₂O₂、O^-·₂含量,根、茎、叶中硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、谷氨酸合酶(GOGAT)活性及游离氨基酸、可溶性蛋白、硝态氮含量的影响,并采用主成分分析法筛选出评价CaCl₂缓解NaCl胁迫效应的生理指标。结果表明：与NaCl胁迫相比,盐胁迫幼苗叶片的H2O₂、O^-·₂积累量在5、10 mmol/L CaCl₂处理下显著减少;GOGAT活性在5、10 mmol/L CaCl₂处理下的植株根和茎内以及各浓度 CaCl₂处理的叶内均显著升高, GS、NR活性在10、20 mmol/L CaCl₂处理的根内和10 mmol/L CaCl₂处理的茎内以及5、10、20 mmol/L CaCl₂处理的叶内均显著升高;可溶性蛋白含量在5、10、20 mmol/L CaCl₂处理的根、茎、叶内均显著升高,游离氨基酸含量在10、20 mmol/L CaCl₂处理的根和茎内以及10 mmol/L CaCl₂处理的叶内均显著升高,硝态氮含量在10 mmol/L CaCl₂处理的根和茎内以及5、10、20 mmol/L CaCl₂处理的叶内均显著升高。研究发现,150 mmol/L NaCl胁迫对酸枣幼苗造成明显过氧化伤害,抑制了体内氮代谢;外源CaCl₂可通过促进幼苗根和茎内GS/GOGAT循环对NH₄⁺的同化作用,提高叶片NR活性,加快硝态氮的转化速率,从而增强幼苗对NaCl胁迫的适应性,并以10 mmol/L CaCl₂处理缓解效果最佳;游离氨基酸、GOGAT、NR可以作为CaCl₂缓解幼苗NaCl胁迫伤害的评价指标。     

遮荫对两个基因型玉米叶片解剖结构及光合特性的影响

以耐荫性不同的玉米品种郑单958(ZD958,耐荫性较强)和豫玉22(YY22,耐荫性较弱)为材料,研究了苗期50%遮荫对玉米叶片形态结构和光合特性的影响。结果表明:形态结构上,苗期遮荫处理后,玉米叶片变薄,单位面积叶绿体数目减少,基粒数、基粒厚度和片层数增加,但是YY22的叶绿体大部分发育不良,肿胀呈球形,基粒片层和基质片层出现不同程度的松散;而ZD958大部分叶绿体结构良好,各部分发育基本正常。光合特性上,弱光胁迫使玉米叶片叶绿素含量升高,净光合速率(Pn)、PSⅡ最大光化学量子产量(Fv/Fm)和实际光化学效率(Φ_PSⅡ)降低,胞间CO₂浓度(Ci)和非光化学猝灭(NPQ)增加,但是YY22的Pn、Fv/Fm和Φ_PSⅡ显著下降,Ci和NPQ显著升高;而ZD958的Fv/Fm和Φ_PSⅡ下降幅度较小,且NPQ增加亦不显著。研究结果提示,弱光胁迫对玉米叶片形态结构和光合特性影响较大,且存在基因型差异,耐荫性较强的品种对弱光环境的适应性较强。     

免耕稻田氮肥运筹对土壤NH3挥发及氮肥利用率的影响

通过大田试验,设置5种不同的施肥比例(基肥:分蘖肥:拔节肥:穗肥-2:2:3:3(R1)、3:2:2:3(R2)、4:2:2:2(R3)、4:3:1:2(R4)与0:0:0:0(CK)),研究氮肥运筹对稻田NH₃挥发和氮肥利用率的影响。结果表明,(1)相对于不施肥,施肥显著提高了稻田NH₃挥发量。氮肥施用后,NH₃挥发损失量占施氮量的6.2%-8.5%,其中,以分蘖期NH₃挥发损失量最大,齐穗期次之,苗期和拔节期最小。施肥处理间,处理R1稻田累积NH₃挥发量最小,显著低于其它施肥处理,比处理R2、R3和R4分别低9.1%(P<0.05)、10.9%(P<0.05)和17.7%(P<0.05)。(2)相关分析表明,田面水NH₄⁺、pH值和土壤NH₄⁺和pH值均与稻田土壤NH₃挥发通量呈显著或者极显著相关;(3)处理R1水稻氮肥利用率相对于处理R2、R3和R4增加了28.4%(P<0.05)、55.4%(P<0.05)和74.9%(P<0.05)。研究表明,氮肥后移能有效降低免耕稻田NH₃挥发,提高水稻的氮肥利用率。     

4种幼树对二氧化硫胁迫的抗性生理响应

利用密闭环境控制室熏气处理,研究了不同浓度（自然状态和0.5、1.5、3.0 mg·L^-1）SO₂对盆栽巨桉、天竺桂、西蒙得木和茶树幼树叶片渗透调节物质含量、抗氧化系统保护酶活性和丙二醛含量的影响,并就各树种对SO₂的抗性进行综合评价。结果显示:（1）SO₂对4个树种叶片伤害程度表现为天竺桂<西蒙得木<巨桉<茶树。（2）SO₂胁迫显著增加了巨桉和西蒙得木叶片可溶性蛋白（SP）、可溶性糖（SS）和游离脯氨酸（Pro）3种渗透调节物质含量;SO₂胁迫对天竺桂叶片SP和SS含量无显著影响,且对Pro含量的促进作用也是在处理30 d后才体现出来;SO₂胁迫对茶树叶片SP含量无显著影响,使SS含量显著降低,而使Pro含量显著增加。（3）SO₂胁迫总体使巨桉和天竺桂抗氧化系统保护酶——超氧化物酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性和丙二醛（MDA）含量增加,但西蒙得木各指标表现不同,而使茶树抗氧化系统保护酶活性和丙二醛含量则全面下降。（4）巨桉、天竺桂、西蒙得木、茶树的最大净吸收S量依次为1.17、1.32、2.04、0.95 g·kg^-1。（5）通过隶属函数法综合7个生理指标得到的SO₂抗性综合排序为天竺桂>西蒙得木>巨桉>茶树,与叶片伤害程度表现一致。研究表明,植物抗氧化保护酶系统在4个树种抵抗SO₂胁迫调节机制中具有重要作用,其中天竺桂超高的基础POD活性可能是其抵抗SO₂伤害的关键机制之一。     

高大气CO2浓度下小麦旗叶光合能量利用对氮素和光强的响应

采用开顶式气室盆栽培养小麦,设计2个大气CO₂浓度、2个光照强度和2个氮水平的组合处理,通过测定小麦叶片光合速率-胞间CO₂浓度响应曲线和叶绿素荧光参数,来测算小麦叶片光化学速率、光合电子传递速率以及叶绿体磷酸丙糖利用效率(TPU)等参数,研究施氮量和光强对高大气CO₂浓度下小麦旗叶光合能量传递与分配的影响,以阐明全球气候变化下植物光合能量分配对光合作用适应性下调的作用机制及其氮素调控。结果表明,大气CO₂浓度升高后小麦叶片的光呼吸电子传递速率(J₀)和Rubisco氧化速率(V₀)显著下降;光合电子流的光化学传递速率(J_C)、Rubisco羧化速率(V_C)和TPU则明显升高,而且施氮后变化幅度加大;小麦叶片J_C/J_F(PSⅡ反应中心总电子流速率)和TPU/V_C显著增加,经过PSⅡ反应中心的电子流更多地进入碳同化过程,表现较高的光合速率(P_n)。遮荫提高了叶片光化学速率和PSⅡ反应中心总电子流速率(J_F),这一作用在低氮叶片尤为突出,但使得J₀和V₀明显升高,并显著降低J_C/J_F,所以P_n明显下降。正常光照条件下,增施氮素可提高小麦叶片的J_F、J_C、V_C和TPU,并使高大气CO₂浓度下J₀和V₀较正常大气CO₂浓度处理显著降低,有效地提高了植物叶片对光能的利用效率;遮荫后高大气CO₂浓度下小麦叶片J_C、V_C、TPU、J_C/J_F和TPU/V_C显著高于正常大气CO₂浓度处理,而且这一变化不受氮素水平的显著调节。因此,氮素在高大气CO₂浓度下对小麦叶片光合能量利用的调节因光强而异,正常光照下可显著改善小麦叶片对光合能量的利用状况,而遮荫后这一作用减弱。     

Effect of NaCl on photosynthesis,salt accumulation and ion compartmentation in two mangrove species, Kandelia candel and Bruguiera gymnorhiza

In a 4-week study, we investigated the effects of increasing soil NaCl (100–400 mM) on photosynthesis, salt uptake and transport, and intracellular compartmentation of Na⁺ and Cl⁻ in 1-year-old seedlings of Kandelia candel (L.) Druce and Bruguiera gymnorhiza (L.) Savigny. Increasing NaCl stress significantly elevated Na⁺ and Cl⁻ in root and shoot tissues (stem + leaf) of both species, but B. gymnorhiza showed a rapid Na⁺ accumulation upon the initiation of salt stress and leaves contained 90% more Na⁺ and 40% more Cl⁻ than K. candel at the end of experiment. Net photosynthetic rate (Pn) declined with increasing salinity, and the most marked reduction occurred after exposure of mangrove seedlings to a severe salinity, 400 mM NaCl. However, the inhibitory effects of severe stress varied with species: Pn decreased by 80% in K. candel whereas in B. gymnorhiza the decline was 60%. The quantum yield (AQY) and carboxylation efficiency (CE) response to severe salinity showed a trend similar to Pn, in which a lesser reduction of AQY and CE was observed in B. gymnorhiza (33–35%), as compared to K. candel (43–52%). X-ray microanalysis of leaf mesophyll cells showed evidence of distinct vacuolar compartmentation of Na⁺ in K. candel but Cl⁻ in B. gymnorhiza after seedlings were subjected to 100 mM NaCl for 7 d. Moreover, Na⁺ within cell wall, cytoplasm, vacuole and chloroplast remained 23–72% lower in stressed B. gymnorhiza as compared to K. candel. In conclusion, B. gymnorhiza exhibited effective salt exclusion from chloroplasts although increasing salt stress caused a rapid and higher build up of Na⁺ and Cl⁻ in the leaves. We suggest that the salt-induced Pn reduction in the two mangrove species is correlated with the ability to exclude Na⁺ and Cl⁻ from the chloroplast, rather than with the bulk leaf salt concentration.     

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。     

Methyl jasmonate regulated diploid and tetraploid black locust (<Emphasis Type="Italic">Robinia pseudoacacia</Emphasis> L.) tolerance to salt stress

Methyl jasmonate (MeJA) is an essential and promising plant growth regulation factor that can improve plant development and growth. Here, we explored the mechanism by which MeJA regulates the tolerance of black locust (Robinia pseudoacacia L.) to salt stress. In this study, diploid and tetraploid R. pseudoacacia were subjected to three treatments: 500 mM NaCl; 100 μM MeJA; and 500 mM NaCl and 100 μM MeJA, and the changes in plant growth, endogenous MeJA levels and the anti-oxidative metabolism of leaves were investigated. The results showed that salt stress significantly inhibited plant growth and induced the accumulation of Na⁺ and Cl^? ions, malondialdehyde (MDA) content and reactive oxygen species. However, these adverse effects could be alleviated by applying MeJA, which was followed by a marked increase in the activities of antioxidant enzymes. In addition, some genes encoding several antioxidant enzymes were also up-regulated. Simultaneously, the endogenous MeJA content in MeJA-treated plants was lower than in salt-treated plants. It is noteworthy that tetraploids always possessed higher salt tolerance and obtained greater positive effects from MeJA than diploids. These results suggested that MeJA might play a protective role in defense responses, enabling diploid and tetraploid black locust, especially tetraploid, to better tolerate the adverse effects of salt stress.     

Influence of NaCl and Na2SO4 on the kinetics and dye decolorization ability of crude laccase from Ganoderma lucidum

In a solid state medium using yellow passion fruit waste as substrate, the basidiomycete Ganoderma lucidum produced a laccase as the main ligninolytic enzyme. This crude enzyme presented Michaelian behavior with both substrates tested, namely 3-ethylbenzthiazoline-6-sulphonic acid (ABTS) and the anthraquinone dye remazol brilliant blue R (RBBR). The K_M’s for these substrates were, respectively, 0.232 × 10⁻³ and 0.602 × 10⁻³ M. The actions of NaCl and Na₂SO₄, two important salts usually found in textile wastewaters, were investigated. The enzyme was inhibited by NaCl, but not by Na₂SO₄. Inhibition by NaCl was of the mixed type with two different inhibition constants. The enzyme was able to completely decolorize RBBR in the presence of 1.0 M Na₂SO₄ and 50% decolorization was found in the presence of 0.1 M NaCl. Such properties certainly make the enzyme a good agent for textile dye effluent treatment considering the fact that wastewaters of this industry usually contain high concentrations of NaCl and Na₂SO₄.     

四翅滨藜生理生化特征对盐胁迫的响应

采用温室盆栽试验研究四翅滨藜(Atriplex canescens)幼苗株高、地径、生物量、净光合速率、蒸腾速率、气孔导度、叶绿素含量、抗氧化酶活性及丙二醛含量对不同浓度NaCl和Na_2SO_4(0、100、200、300和400mmol·L~(-1))胁迫的响应,以探讨四翅滨藜对不同种类及不同浓度盐渍环境的适应机制及其耐盐机理。结果显示:(1)随着盐分浓度的升高,四翅滨藜幼苗的株高、地径及生物量增量呈现出先升高后降低的趋势,低盐浓度下2种盐均促进幼苗生长,盐浓度超过400mmol·L~(-1)时,NaCl对幼苗生长具有明显抑制作用。(2)2种盐处理下,四翅滨藜幼苗净光合速率(Pn)和叶绿素含量(Chl)随盐浓度增大而升高,即2种盐均对幼苗Pn和Chl含量具有促进作用,且Na_2SO_4的促进效果大于NaCl;而幼苗蒸腾速率(Tr)和气孔导度(Gs)随盐浓度升高呈先增大后减小的趋势,且Na_2SO_4的促进作用强于NaCl。(3)与对照相比,四翅滨藜幼苗的丙二醛、SOD、POD酶活性在NaCl和Na_2SO_42种盐处理下,随着盐浓度的升高均呈现出不同程度的增大,且增大幅度总体表现为NaClNa_2SO_4。研究表明,四翅滨藜在NaCl和Na_2SO_4胁迫下,叶绿素的分解速率以及发挥作用的渗透调节物质均有差异,使得幼苗叶片健康程度不同,导致叶片光合能力大小的差异,最终表现为植株的生长差异;四翅滨藜具有较强的耐盐能力,而且对Na_2SO_4的适应能力强于NaCl。     

Fatty acid desaturase-6 (Fad6) is required for salt tolerance in Arabidopsis thaliana

Fatty acid desaturases play important role in plant responses to abiotic stresses including cold, high temperature, drought, and osmotic stress. In this work, we provide the evidence that Fad6, a chloroplast desaturase, is required for salt tolerance during the early seedling development of Arabidopsis. Expression of Fad6 was responsive to salt and osmotic stress. Compared with the wild-type plants, the fad6 mutant showed reduced tolerance to salt stress, and accumulated more Na⁺ and less K⁺ under high NaCl stress condition. Furthermore, cellular oxidative damage was more severe in fad6 when treated with high concentrations of NaCl, as indicated by increased electrolyte leakage rate and malondialdehyde production, as well as by decreased activities of anti-oxidative enzymes. All these results suggest that Fad6 is required for salt resistance in Arabidopsis.     

Knock-out of Arabidopsis AtNHX4 gene enhances tolerance to salt stress

AtNHX4 belongs to the monovalent cation:proton antiporter-1 (CPA1) family in Arabidopsis. Several members of this family have been shown to be critical for plant responses to abiotic stress, but little is known on the biological functions of AtNHX4. Here, we provide the evidence that AtNHX4 plays important roles in Arabidopsis responses to salt stress. Expression of AtNHX4 was responsive to salt stress and abscisic acid. Experiments with CFP-AtNHX4 fusion protein indicated that AtNHX4 is vacuolar localized. The nhx4 mutant showed enhanced tolerance to salt stress, and lower Na⁺ content under high NaCl stress compared with wild-type plants. Furthermore, heterologous expression of AtNHX4 in Escherichia coli BL21 rendered the transformants hypersensitive to NaCl. Deletion of the hydrophilic C-terminus of AtNHX4 dramatically increased the hypersensitivity of transformants, indicating that AtNHX4 may function in Na⁺ homeostasis in plant cell, and its C-terminus plays a role in regulating the AtNHX4 activity.     

NaCl对齿肋赤藓叶肉细胞超微结构的影响

齿肋赤藓(Syntrichia caninervis)是古尔班通古特沙漠苔藓结皮层中的优势物种,对荒漠生态系统的稳定性及功能多样性具有十分重要的意义。利用透射电镜技术对不同浓度Na Cl胁迫下齿肋赤藓叶肉细胞超微结构进行了观察。结果表明:齿肋赤藓叶肉细胞在未胁迫(0 mmol/L)处理下排列疏松,各种细胞结构完整,叶绿体基质排列均匀且叶绿体内含少量淀粉粒和脂质球。在轻度盐Na Cl胁迫(100 mmol/L)下,齿肋赤藓叶肉细胞结构依然保持完整,叶绿体基质均匀,叶肉细胞超微结构仅有较小变化。在中度盐Na Cl胁迫(200、300 mmol/L)下,齿肋赤藓叶肉细胞发生质壁分离,出现晶体结构,且中央大液泡发生破裂;叶绿体由梭形变成椭球形或圆球状,出现空泡化并伴随有轻微的解体;叶绿体类囊体肿胀,脂质球数量增加。在高度Na Cl胁迫(400、500 mmol/L)下,齿肋赤藓细胞的质壁分离加剧,叶肉细胞出现大量泡状结构和膜片层,叶肉细胞死亡;叶绿体片层结构消失,空泡化加重,脂质球数量增加且体积变大,叶绿体内外膜消失,叶绿体大部分解体,在叶肉细胞中几乎看不到叶绿体的存在。上述结果表明,叶绿体膜结构的损伤与盐胁迫下叶肉细胞死亡有密切关系。