耐盐性不同的小麦根和根茎结合部的拒Na+作用

NaCl处理引起小麦幼苗干重下降,盐敏感品种比耐盐品种下降幅度要大.盐敏感品种的拒Na+能力为35%左右,耐盐品种的拒Na+能力为50%～60%左右,这表明耐盐品种的拒Na+能力远远大于盐敏感品种.不同耐盐性小麦的拒Na+部位不同,盐敏感品种的拒Na+部位主要在根茎结合部,而耐盐品种的拒Na+部位主要在根部.     

耐盐性不同的小麦根和根茎结合部的拒Na^＋作用

NaCl处理引起小麦幼苗干重下降,盐敏感品种比耐盐品种下降幅度要大,盐敏感品种的拒Na 能力为35％左右,耐盐品种的拒Na＋能力为50％－60％左右。这表明耐盐品种的拒Na能力远远大于盐敏感品种,不同耐盐性小麦的拒Na＋倍位不同,盐敏感品种的拒Na 部位主要在根茎结合部,而耐盐品种的拒Na 部位主要在根部。     

小麦幼苗拒Na+部位的拒Na+机理

采用日立Z 80 0 0原子吸收分光光度计测Na 、K 含量 ,采用不连续蔗糖梯度离心分离质膜和液泡膜微囊。递增盐度和盐冲击处理下 ,耐盐品种德抗 96 1的SK ,Na(吸收 ) 值和SK ,Na(运输 ) 值均明显大于盐敏感品种鲁麦 15 ;德抗 96 1根部和鲁麦 15根茎结合部Na 含量均呈递增趋势 ,表现出累积效应 ;德抗 96 1根细胞质膜微囊和液泡膜微囊H ATP酶活性均明显大于鲁麦15 ,鲁麦 15根茎结合部液泡膜微囊H ATP酶活性大于德抗 96 1,在同一品种的植株里 ,盐冲击的根和根茎结合部细胞质膜微囊和液泡膜微囊H ATP酶活性均小于递增盐度的酶活性。小麦拒Na 部位细胞质膜和液泡膜H ATP酶活性与其耐盐性强弱成正相关     

不同耐盐性小麦根Na~+和K~+的吸收特性

以耐盐小麦品种‘德抗961’和盐敏感小麦品种‘鲁麦15’为材料,研究小麦根Na+、K+吸收特性及其与耐盐性关系。结果表明,2个小麦品种根K+吸收动力学曲线均符合Michaelis-Menten方程,即V=Vmax×[S]/([S]+Km)+k×[S]。低浓度(低于25mmol·L-1)NaCl处理对根高亲和K+吸收系统转运K+具有促进作用,对耐盐品种‘德抗961’的促进作用更大。小麦根高亲和K+吸收系统是通过K+/H+同向转运,而不是K+/Na+同向转运。NaCl处理对根低亲和K+吸收系统有抑制作用,对盐敏感品种‘鲁麦15’的抑制作用更大。NaCl处理导致2个小麦品种根和叶片中的K+含量显著下降,Na+含量显著升高,但‘德抗961’根和叶片中的K+含量均显著高于‘鲁麦15’,‘德抗961’根中Na+含量显著高于‘鲁麦15’,而其叶片中Na+含量显著低于‘鲁麦15’,从而保证NaCl胁迫下其叶片较高的K+/Na+比。非选择性阳离子通道是小麦根Na+吸收的主要途径,K+通道是Na+吸收的一条重要途径。这些结果表明小麦部分通过调节根系K+吸收系统而维持叶片较高的K+/Na+比,从而提高其耐盐性。     

盐胁迫下水稻叶绿体中Na~ 、Cl~-积累导致叶片净光合速率下降

研究了 0～ 2 0 0mmol/L的NaCl胁迫下耐盐性不同的水稻品种Pokkali(耐盐 )和Peta(盐敏感 )根系、叶片和叶绿体中Na 、K 和Cl-含量的变化及其与叶片光合作用的关系。结果表明 :随着NaCl胁迫时间和浓度的增加 ,供试 2个品种在根、叶片和叶绿体中Na 、Cl-含量增加 ,K 含量下降。耐盐品种体内Na 、Cl-含量增加或K 含量减少的幅度小于盐敏感品种。在 2 0 0mmol/L的NaCl胁迫下盐敏感品种根、叶片和叶绿体中的Na /K 分别是耐盐品种的 2 0 8%、30 8%和 2 97%。与Na 相比 ,耐盐品种根系对K 的吸收和向叶片运输的选择性 (SK ,Na)较强。但在经过0、10 0和 2 0 0mmol/L的NaCl处理后 2个品种叶绿体中的Na /K 均高于叶片 (SK ,Na均小于 1)。盐胁迫下水稻叶绿体中Na 、Cl-含量和Na /K 与叶片净光合速率呈极显著负相关。     

NaCl胁迫对不同耐盐性玉米自交系萌动种子和幼苗离子稳态的影响

盐胁迫影响植物组织的离子分布,不同品种间存在差异。以玉米耐盐自交系81162和8723及盐敏感自交系P138为材料,研究了不同浓度(0、60、140、220 mmol/L)Na Cl胁迫下萌动期种子和幼苗的不同部位中Na+、K+、Ca2+含量以及K+/Na+和Ca2+/Na+比值的变化,旨在探讨不同自交系耐盐性差异的原因。结果表明,在萌动种子中,3个玉米自交系中的Na+积累量表现为种皮胚胚乳,K+累积表现为胚种皮胚乳;幼苗中,Na+积累表现为根茎叶。随着Na Cl浓度的增加,3个玉米自交系萌动种子和幼苗中的Na+含量逐渐升高,但是萌动种子中耐盐自交系81162和8723的Na+增加幅度小于盐敏感自交系P138,Na+含量小于盐敏感自交系P138;幼苗中耐盐自交系81162和8723的Na+增加幅度大于盐敏感自交系P138,幼苗根中Na+含量大于盐敏感自交系P138;茎叶中的Na+含量小于盐敏感自交系P138。随着Na Cl浓度的增加,萌动种子和幼苗中的K+和Ca2+含量逐渐降低。K+离子在耐盐自交系81162和8723萌动种子和幼苗中的降低幅度小于盐敏感自交系P138;Ca2+离子在耐盐自交系81162和8723幼苗中的降低幅度小于盐敏感自交系P138;而在萌动种子中3个自交系Ca2+的流失差异不大。耐盐自交系81162和8723萌动种子和幼苗中K+含量都大于盐敏感自交系P138。耐盐自交系81162和8723的萌动种子和幼苗根中Ca2+含量都大于盐敏感自交系P138;幼苗叶片中则小于盐敏感自交系P138。萌动种子和幼苗中K+/Na+和Ca2+/Na+均随着Na Cl浓度的升高而降低,K+/Na+比值表现为耐盐自交系81162和8723大于盐敏感自交系P138。耐盐自交系81162和8723通过调节离子平衡维持萌动种子和幼苗中较高的K+/Na+比值从而提高耐盐性。     

西藏小麦耐盐性鉴定及分析

在3种不同盐胁迫浓度下对161份来源于西藏的小麦材料进行了苗期耐盐性鉴定,其中有147份西藏半野生小麦及14份密穗小麦.以普通小麦耐盐品种茶淀红麦和盐敏感品种PI94341为对照.在147份西藏半野生小麦中有14份表现为耐盐,占9.5%.14份密穗小麦中没有发现耐盐材料.在这161份材料中还发现了3份对盐胁迫浓度梯度不敏感的品种.结果表明,我国特有的西藏半野生小麦中蕴藏有丰富的耐盐种质,它们可供小麦耐盐育种用做亲本.     

西藏小麦耐盐性鉴定及分析

在3种不同盐胁迫浓度下对161份来源于西藏的小麦材料进行了苗期耐盐性鉴定,其中有147份西藏半野生小麦及14份密穗小麦。以普通小麦耐盐品种荼淀红麦和盐敏感品种P194341为对照。在147份西藏半野生小麦中有14份表现为耐盐,占9．5％。14份密穗小麦中没有发现耐盐材料。在这161份材料中还发现了3份对盐胁迫浓度梯度不敏感的品种。结果表明,我国特有的西藏半野生小麦中蕴藏有丰富的耐盐种质,它们可供小麦耐盐育种用做亲本。     

不同抗盐性小麦叶鞘的Na+/K+选择性

以200mmol／LNaCl处理耐盐小麦（Triticum aestivum L．）品种DK961和盐敏感小麦品种LM153d后,DK961叶鞘中Na^＋含量和叶片中K^＋含量均显著高于LMl5,这造成DK961叶片中Na^＋／K^＋比显著低于LM15。即DK961的叶鞘以其较LM15更强的限制Na^＋、推动K^＋向叶片运输的能力来保持叶片相对较低的Na^＋／K^＋比,即叶鞘在小麦抗盐性中可能起重要作用。     

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.     

Quantifying the three main components of salinity tolerance in cereals

Salinity stress is a major factor inhibiting cereal yield throughout the world. Tolerance to salinity stress can be considered to contain three main components: Na⁺ exclusion, tolerance to Na⁺ in the tissues and osmotic tolerance. To date, most experimental work on salinity tolerance in cereals has focused on Na⁺ exclusion due in part to its ease of measurement. It has become apparent, however, that Na⁺ exclusion is not the sole mechanism for salinity tolerance in cereals, and research needs to expand to study osmotic tolerance and tissue tolerance. Here, we develop assays for high throughput quantification of Na⁺ exclusion, Na⁺ tissue tolerance and osmotic tolerance in 12 Triticum monococcum accessions, mainly using commercially available image capture and analysis equipment. We show that different lines use different combinations of the three tolerance mechanisms to increase their total salinity tolerance, with a positive correlation observed between a plant's total salinity tolerance and the sum of its proficiency in Na⁺ exclusion, osmotic tolerance and tissue tolerance. The assays developed in this study can be easily adapted for other cereals and used in high throughput, forward genetic experiments to elucidate the molecular basis of these components of salinity tolerance.     

Anatomical changes in stem and root of soybean plants submitted to salt stress

• The soybean is a legume that is widely cultivated in many countries due to the high levels of protein and oil contained in its seed, and is used for human and animal nutrition. However, salinity affects more than 800 million hectares worldwide, limiting global agricultural production.
• The aim of this research was to evaluate the structural behaviour of the roots and stems under progressive salt stress, detailing the possible anatomical modifications to these organs in soybean plants during this stress. The plants were randomized into five treatments (0, 50, 100, 150 and 200 mm NaCl).
• All the root regions studied and exposed to 100 mm Na⁺ exhibited increases in the epidermis and endodermis and formation of lysogenic aerenchyma with increasing salinity, revealing the protective roles of these structures in reducing Na⁺ influx. In the stem, increases in the cortex and pith in the first internode subject to 100 mm Na⁺ suggest anatomical responses that aim to minimize oxidative stress.
• Soybean plants subjected to progressive salt stress (>50 mm Na⁺) avoided cavitation and loss of function linked to vessel elements, reducing the metaxylem in all the root and stem regions analysed. Finally, our results confirm anatomical changes to the roots and stems.

     

Sodium exclusion mechanisms at the root surface of two maize cultivars

Sodium exclusion at the root surface of intact plants was investigated in two maize cultivars (Zea mays L. cv. Pioneer 3906 and cv. DeKalb XL75). The strong sodium exclusion by Pioneer 3906 relative to DeKalb XL75 was not caused by larger efflux rates. In contrast, this cultivar showed reduced influx rates resulting in about half the net uptake in comparison with DeKalb XL75. It is concluded that the cultivar difference in sodium exclusion at the root surface is based on a relatively low passive sodium permeability of the epidermal and cortex plasmalemma of Pioneer 3906. For both cultivars, the flux ratio equation indicated an active component of sodium efflux.     

Sodium transport measured in plasma membrane vesicles isolated from wheat genotypes with differing K+/Na+ discrimination traits

Right-side-out plasma membrane vesicles were isolated from wheat roots using an aqueous polymer two-phase system. The purity and orientation of the vesicles were confirmed by marker enzyme analysis. Membrane potential (Ψ)-dependent ²²Na⁺ influx and sodium/proton (Na⁺/ H⁺) antiport-mediated efflux across the plasma membrane were studied using these vesicles. Membrane potentials were imposed on the vesicles using either K⁺ gradients in the presence of valinomycin or H⁺ gradients. The ΔΨ was quantified by the uptake of the lipophilic cation tetraphenylphosphonium. Uptake of Na⁺ into the vesicles was stimulated by a negative ΔΨ and had a K_m for extrav-esicular Na⁺ of 34.8 ± 5.9 mol m³. The ΔΨ-dependent uptake of Na⁺ was similar in vesicles from roots of hexaploid (cv. Troy) and tetraploid (cv. Langdon) wheat differing in a K⁺/Na⁺ discrimination trait, and was also unaffected by growth in 50 mol m^?3 NaCl. Inhibition of ΔΨ-dependent Na⁺ uptake by Ca²⁺ was greater in the hexaploid than in the tetraploid. Sodium/proton antiport was measured as Na⁺-dependent, amiloride-inhibited pH gradient formation in the vesicles. Acidification of the vesicle interior was measured by the uptake of ¹⁴C-methylamine. The Na⁺/H⁺ antiport had a K_m, for intravesicular Na⁺ of between 13 and 19 mol m^?3. In the hexaploid, Na⁺/H⁺ antiport activity was greater when roots were grown in the presence of 50 mol m^?3NaCl, and was also greater than the activity in salt-grown tetraploid wheat roots. Antiport activity was not increased in a Langdon 4D chromosome substitution line which carries a trait for K⁺/Na⁺ discrimination. It is concluded that neither of the transport processes measured is responsible for the Na⁺/K⁺ discrimination trait located on the 4D chromosome of wheat.     

Nonlabens Dokdonensis视紫红质2中的钠离子结合与pH依赖性的传递

光驱动钠离子泵是近年来发现的全新的光遗传学工具蛋白,在光激发下向膜外主动运输钠离子。然而,其钠离子传递的机制仍不清楚。该家族成员NdR2的可见吸收光谱、荧光光谱和等温滴定量热的结果说明：基态下的NdR2不结合钠离子。进一步的钠离子传递动力学和功能实验发现NdR2在酸性条件下的钠离子传递发生改变。这种pH依赖性的钠离子传递有助于深入理解光驱动钠离子泵中的钠离子的传递机制。     

Reassessment of tissue Na(+) concentration as a criterion for salinity tolerance in bread wheat

Wheat is the most important crop grown on many of world's saline and sodic soils, and breeding for improved salinity tolerance (ST) is the only feasible way of improving yield and yield stability under these conditions. There are a number of possible mechanisms by which cereals can tolerate high levels of salinity, but these can be considered in terms of Na(+) exclusion and tissue tolerance. Na(+) exclusion has been the focus of much of the recent work in wheat, but with relatively little progress to date in developing high-yielding, salt-tolerant genotypes. Using a diverse collection of bread wheat germplasm, the present study was conducted to assess the value of tissue Na(+) concentration as a criterion for ST, and to determine whether ST differs with growth stage. Two experiments were conducted, the first with 38 genotypes and the second with 21 genotypes. A wide range of Na(+) concentrations within the roots and shoots as well as in ST were observed in both experiments. However, maintenance of growth and yield when grown with 100 mM NaCl was not correlated with the ability of a genotype to exclude Na(+) either from an individual leaf blade or from the whole shoot. The K(+) : Na(+) ratio also showed a wide range among the genotypes, but it did not explain the variation in ST among the genotypes. The results suggested that Na(+) exclusion and tissue tolerance varied independently, and there was no significant relationship between Na(+) exclusion and ST in bread wheat. Consequently, similar levels of ST may be achieved through different combinations of exclusion and tissue tolerance. Breeding for improved ST in bread wheat needs to select for traits related to both exclusion and tissue tolerance.     

Na+、葡萄糖、果糖对凹目白鲑精子活力的影响

研究了凹目白鲑（Coregonus autumnalis）精子在302．6～488．9kPa时的NaCl溶液、D-葡萄糖溶液及D-果糖溶液中的活动情况。结果显示,在NaCl溶液中凹目白鲑精子在395．7kPa具最佳活力,其快速运动时间（fast movement time,FT）与寿命时间（1ife time,LT）的最大值分别达43．57s和90．31s;与相同渗透压下NaCl溶液相比,凹目白鲑精子在葡萄糖和果糖溶液中的FT与LT均有不同程度的增加;在葡萄糖溶液中FT与LT的最大值分别为57．67s和97．29s,在果糖溶液中则为70．44s和105．29s。说明凹目白鲑精子活力不但与溶液渗透压有关,而且与溶液溶质有关。     

State-Dependent Block of Na<Superscript>+</Superscript> Channels by Articaine Via the Local Anesthetic Receptor

Articaine is widely used as a local anesthetic (LA) in dentistry, but little is known regarding its blocking actions on Na⁺ channels. We therefore examined the state-dependent block of articaine first in rat skeletal muscle rNav1.4 Na⁺ channels expressed in Hek293t cells. Articaine exhibited a weak block of resting rNav1.4 Na⁺ channels at −140 mV with a 50% inhibitory concentration (IC₅₀) of 378 ± 26 μM (n = 5). The affinity was higher for inactivated Na⁺ channels measured at −70 mV with an IC₅₀ value of 40.6 ± 2.7 μM (n = 5). The open-channel block by articaine was measured using inactivation-deficient rNav1.4 Na⁺ channels with an IC₅₀ value of 15.8 ± 1.5 μM (n = 5). Receptor mapping demonstrated that articaine interacted strongly with a D4S6 phenylalanine residue, which is known to form a part of the LA receptor. Thus the block of rNav1.4 Na⁺ channels by articaine is via the conserved LA receptor in a highly state-dependent manner, with a ranking order of open (23.9×) > inactivated (9.3×) > resting (1×) state. Finally, the open-channel block by articaine was likewise measured in inactivation-deficient hNav1.7 and rNav1.8 Na⁺ channels, with IC₅₀ values of 8.8 ± 0.1 and 22.0 ± 0.5 μM, respectively (n = 5), indicating that the high-affinity open-channel block by articaine is indeed preserved in neuronal Na⁺ channel isoforms.