盐胁迫下黄芩种子萌发及幼苗对外源抗坏血酸的生理响应

以黄芩(Scutellaria baicalensis)种子为材料,用氯化钠(Na Cl)模拟盐胁迫条件,采用纸上发芽,研究外源抗坏血酸(As A)对盐胁迫下黄芩种子萌发及幼苗的影响。结果表明,在80 mmol·L-1 Na Cl胁迫下,黄芩种子萌发及幼苗生理指标受到显著抑制;0.50 mmol·L-1 As A处理可显著提高盐胁迫下黄芩种子的发芽势(GE)、发芽率(GR)、发芽指数(GI)、简化活力指数(SVI)以及根系总黄酮、可溶性糖和脯氨酸(Pro)含量,同时也可显著提高幼苗根系活力和超氧化物歧化酶(SOD)活性,显著降低丙二醛(MDA)含量。这说明适宜浓度的抗坏血酸能提高黄芩种子的萌发能力和幼苗对盐胁迫的适应能力,从而起到缓解盐胁迫对种子萌发及幼苗生长的抑制作用。     

NaCl和Na2CO3胁迫对桑树幼苗生长和光合特性的影响

以1年生“青龙桑”幼苗为试验材料,研究了中性盐(NaCl)和碱性盐(Na2CO3)胁迫下桑树幼苗的生长和叶片光合特性.结果表明:盐胁迫明显降低了桑树幼苗的株高、叶片数、生物量和叶片的光合能力.随着Na+浓度的增加,桑树叶片的气孔导度、蒸腾速率、净光合速率、实际光化学效率、电子传递速率和光化学猝灭系数明显降低,过剩光能以非光化学猝灭形式耗散的比例增加,桑树叶片的光能转化效率和光合能力下降.在Na+浓度＜150 mmol·L-1时,桑树幼苗的光合能力和生长受到的抑制较小,通过增加根冠比进一步适应盐胁迫,但这种保护机制随着盐浓度的增加逐渐降低.在Na2CO3胁迫下,＞50 mmol·L-1 Na+浓度对桑树的生长和光合能力表现出较强的抑制作用,并随Na+浓度的增加,抑制程度加大.在NaCl＜ 150mmol·L-1时,桑树的光合能力主要依赖植株形态和光合代谢双重途径适应中性盐逆境,而在NaC1浓度＞150 mmol·L-1和碱性盐胁迫下,其主要依赖光合代谢来适应逆境.     

不同耐盐性药用甘草幼苗根对Na~+的响应及其维管组织变化

以甘草属2种耐盐植物胀果甘草、乌拉尔甘草为材料,用不同浓度(50、100、150、200、250mmol·L-1)NaCl处理幼苗21d后,分析其生物量和根、茎、叶中的Na+、K+含量以及K+/Na+,计算根的离子选择吸收和运输系数,并应用光学显微镜观察比较二者的维管组织结构变化,以揭示2种药用甘草幼苗根对Na+的响应及其维管组织结构的变化特征,探讨甘草的耐盐机理。结果表明:(1)NaCl胁迫使2种甘草幼苗生物量均下降,在NaCl浓度为250mmol·L-1时,胀果甘草、乌拉尔甘草幼苗生物量分别是对照的53.34%、46.21%,胀果甘草耐盐性强于乌拉尔甘草。(2)随着NaCl浓度上升,2种甘草根积累的Na+显著增多,其中胀果甘草在所有盐处理下,根Na+含量均高于其它器官,说明其根对吸收的Na+具有显著截留效应;而乌拉尔甘草只在0~150mmol·L-1 NaCl范围内,根Na+含量显著高于叶片,当NaCl为200、250mmol·L-1时,叶片Na+含量显著高于根,说明乌拉尔甘草根对Na+的截留能力有限。(3)在相同盐处理下,胀果甘草离子选择吸收系数SAK,Na、离子运输系数STK,Na均大于乌拉尔甘草,胀果甘草根抑制Na+、促进K+向地上部运输的能力强于乌拉尔甘草。(4)乌拉尔甘草在NaCl为150、200mmol·L-1、胀果甘草在250mmol·L-1时,根结构对盐胁迫产生应激性响应,维管组织比例显著上升,有助于提高根向上的运输能力,减少盐害。研究表明,2种药用甘草根对Na+截留作用和向上运输时促K+抑Na+能力的差异,是导致其耐盐能力不同的主要原因,根对Na+的积累和截留作用的差异与根的结构响应相吻合,能较好地解释二者的耐盐性差异。     

DCPTA对盐胁迫下玉米苗期根系生长、渗透调节及膜透性的影响

黑龙江省西部地区盐碱土面积约有66.7×104hm2,制约着黑龙江省粮食生产水平的进一步提高。叔胺类活性物质2-(3,4-二氯苯氧基)-乙基-二乙胺(DCPTA)具有提高作物抗逆性作用,为探讨DCPTA提高玉米耐盐性机制,采用营养液水培试验,在前期试验基础之上,选取"先玉335"(耐盐性强)和"丰禾1号"(耐盐性弱)2个品种,研究DCPTA(15mg·L-1)对Na Cl胁迫下(150 mmol·L-1)玉米幼苗根系生长、渗透调节及质膜透性的影响。结果表明:DCPTA能增加盐胁迫下幼苗的根长、根表面积、根体积、根鲜重和根干重,缓解盐胁迫对根系生长的抑制;DCPTA维持了根系水分平衡,提高了盐胁迫下幼苗根系相对含水量,"先玉335"和"丰禾1号"分别提高3.6%和6.4%;DCPTA通过提高根系可溶性糖含量和可溶性蛋白含量,降低幼苗根系脯氨酸含量,增强了盐胁迫下玉米幼苗根系的渗透调节能力,并通过降低根系丙二醛(MDA)含量和相对电导率,保护了根系质膜结构和功能;与盐胁迫相比,"先玉335"丙二醛含量和相对电导率分别降低21.6%和24.2%,"丰禾1号"分别降低28.1%和30.4%;DCPTA缓解盐胁迫对根系伤害的效果表现为"丰禾1号""先玉335"。     

不同盐处理对玉米幼苗根系质子分泌及细胞膜透性的影响

以玉米品种郑单958为实验材料,分别用100 mmol/L NaCl、100 mmol/L KCl和50 mmol/L Na2CO3处理其幼苗3 d,研究不同盐类对玉米根系质子分泌和细胞膜透性的影响.结果表明:不同盐处理都显著抑制玉米幼苗根系的生长,抑制程度依次为Na2CO3>KCl>NaCl;不同盐处理均使玉米幼苗根系Na 含量显著增加,NaCl和Na2CO3处理显著降低根系K 含量而导致其Na /K 升高,但KCl处理却显著提高根系K 含量使其Na /K 降低;不同盐处理均能显著增加细胞膜透性而降低根系质子分泌能力,影响程度依次为Na2CO3>KCl>NaCl.研究发现,相同阳离子浓度条件下,KCl处理对玉米根系质子分泌的抑制作用强于NaCl,碱性盐的抑制作用大于中性盐;盐胁迫可能通过改变玉米幼苗根系质膜的稳定性来影响质子分泌,从而抑制根系生长.     

多效唑浸种对NaCl胁迫麻疯树幼苗的生长调节效应

以'南油1号'麻风树幼苗为材料,通过盆栽试验研究了200 mmol·L-1 NaCl胁迫处理对不同浓度(0～1 000 mg·L-1)多效唑(PP333)浸种麻疯树幼苗生长和光合作用的影响.结果显示:在盐胁迫下,不同浓度的PP333浸种处理均显著降低麻疯树植株株高,但是均显著提高了盐胁迫下株高相对生长速率,同时提高了其干物质积累速率、根含水量、根冠比、叶绿素含量和净光合速率;并提高了幼苗根、叶的K+含量,降低根、叶的Na+和Cl-含量,从而提高根、叶的K+/Na+比率.研究表明,PP333浸种能缓解盐胁迫下麻疯树幼苗的失水程度和光合色素的下降幅度,有效改善其光合作用效率,同时维持体内的离子平衡,从而减轻盐胁迫伤害,促进植株生长,并以600 mg·L-1 PP333浸种效果最好.     

盐胁迫对海岛棉不同基因型幼苗生长及生理生态特征的影响

采用水培试验,分析了不同浓度的NaCl(0、50、100、150、200、250 mmol.L-1)处理对两个海岛棉品种新海28号(XH28,耐盐基因型)和新海21号(XH21,盐敏感基因型)植株生长、生物量分配、蛋白质含量、脯氨酸(Pro)含量以及过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)等生理生态指标的影响。研究发现:(1)盐胁迫对海岛棉幼苗鲜重的影响大于干重,对茎叶的影响大于根系;(2)盐处理引起海岛棉幼苗根叶脯氨酸含量的增加;(3)低浓度NaCl处理(≤50 mmol.L-1)显著增加耐盐品种XH28的根长、株高及单株鲜干重;(4)盐胁迫引起海岛棉幼苗根系中可溶性蛋白质含量下降,相反叶片中可溶性蛋白质含量上升;(5)盐胁迫下耐盐品种XH28幼苗中的POD、CAT、APX酶活性明显高于盐敏感品种XH21,但GR活性显著低于XH21。研究表明,低浓度NaCl处理刺激了棉株生长,增加了生物量;盐胁迫下叶内蛋白质、脯氨酸含量明显增加,POD、CAT、APX酶活力升高是海岛棉耐盐品种XH28的基本特征。     

根际通气状况对盐胁迫下棉花幼苗生长的影响

以溶液培养的棉花(Gossypium hirsutum)幼苗为材料,测定了不同盐胁迫程度和不同通气状况下棉花幼苗株高、根系体积、根系和茎叶生物量以及灰分含量的变化,以探索根际通气状况对盐胁迫下棉花生长的影响。结果表明,盐胁迫抑制棉花植株生长,表现为植株变矮、叶面积减小和干物质积累下降;根际环境通气不良也会导致棉花幼苗生长受抑制、干物质积累下降和矿质元素吸收减少等。进一步比较盐胁迫和根际通气状况及两者组合作用对棉苗生长的影响,发现盐胁迫对株高和总生物量的影响较大,而根际通气状况对根系体积、根系生物量、根冠比和矿质元素吸收的影响较大。总体表现为:盐胁迫对茎叶生长的不利影响较大,而根际通气状况对根系生长的不利影响较大。同时,在根际环境通气良好的条件下,不同程度盐胁迫导致的棉花幼苗株高、根系体积、叶面积、根系生物量和总生物量的变化程度远小于根际环境通气不良条件下的变化程度。实验结果表明,根际环境通气良好可以减弱盐胁迫对棉花生长发育的抑制作用,而根际环境通气不良则会加重盐胁迫的不利影响。     

等渗Ca(NO3)2和NaCl胁迫对黄瓜幼苗生长及渗透调节物质含量的影响

采用营养液培养方法,以耐盐性较弱的‘津春2号’黄瓜品种为试材,研究了等渗Ca(NO3)2和NaCl胁迫对黄瓜幼苗生长、根系电解质渗透率、根系活力、Na+和K+含量及渗透调节物质含量的影响。结果显示:(1)在84mmol.L-1 NaCl和56mmol.L-1 Ca(NO3)2等渗胁迫下,黄瓜幼苗鲜重和干重均显著下降,且NaCl处理下降的幅度大于等渗Ca(NO3)2处理。(2)NaCl主要通过对黄瓜根系的伤害来抑制植株生长,表现为根系活力下降、根系质膜透性增大、Na+大量积累、K+含量显著下降、Na+/K+明显上升,最终导致根冠比下降;而Ca(NO3)2处理对根系质膜透性、K+含量、Na+/K+的影响均小于NaCl胁迫,且根系活力和根冠比上升,但Ca(NO3)2胁迫后叶片含水量和渗透调节能力均小于NaCl胁迫。(3)NaCl胁迫条件下,黄瓜幼苗内渗透调节物质以可溶性糖为主,而Ca(NO3)2胁迫以可溶性蛋白为主。研究表明,NaCl胁迫对黄瓜幼苗的伤害大于等渗Ca(NO3)2,NaCl主要通过破坏根系质膜结构影响植株生长,而Ca(NO3)2主要通过引起地上部生理干旱来影响植株生长。     

丛枝菌根真菌(AMF)对盐胁迫下芦笋幼苗生长及体内Na~+、K~+、Ca~(2+)、Mg~(2+)含量和分布的影响

以芦笋盐敏感品种‘NJ978’为材料,采用盆栽试验,研究了接种丛枝菌根真菌(AMF)对Na Cl胁迫下芦笋幼苗生长及体内Na+、K+、Ca2+、Mg2+吸收和分布的影响。结果表明:在Na Cl胁迫下,幼苗株高、鲜重、干重均显著降低,接种AMF可以有效缓解盐胁迫对芦笋幼苗生长的抑制;Na Cl处理的芦笋幼苗根系和地上部Na+含量显著高于对照,K+、Ca2+、Mg2+的含量则显著减少;AMF+Na Cl处理的芦笋幼苗根系K+、Ca2+、Mg2+含量与Na Cl处理相比,分别增加了76.9%、23.1%和22.5%,而Na+含量则减少了27.4%;AMF+Na Cl处理的芦笋幼苗地上部K+、Ca2+、Mg2+含量与Na Cl处理相比,分别增加了58.4%、50.4%和76.0%,而Na+含量则减少了42.3%。与Na Cl处理相比,接种AMF可以降低盐胁迫下芦笋幼苗根系和地上部Na+/K+、Na+/Ca2+、Na+/Mg2+,提高根系选择吸收性ASK,Na、ASCa,Na、ASMg,Na和根系向地上部的选择运输性TSK,Na、TSCa,Na、TSMg,Na。由此表明,盐胁迫下接种AMF可以通过调节芦笋体内的离子平衡,从而缓解盐胁迫对植株的伤害。     

高等植物钾转运蛋白

钾在植物生长发育过程中具有许多重要的作用。以模式植物拟南芥中克隆和鉴定的钾通道和转运体为基础,全面介绍了高等植物中钾转运体系家族,包括Shaker通道、KCO通道、KUP/HAK/KT转运体、HKT转运体和其它转运体。同时,分析了在高等植物中存在多种钾吸收和转运机制的可能原因。     

Comparative effect of potassium chloride and potassium sulfate on the yield and protein content of wheat in three different rotations

Comparative effects of potassium chloride and potassium sulfate at various levels of potassium on the performance of ARZ variety of wheat were studied at Agriculture Research Station Dera Ismail Khan, N.W.F.P., Pakistan. The experiment was laid out in three different rotationsviz, rice-wheat, maize-wheat and fallow-wheat. Potassic fertilizers were applied at the rate of 0, 37, 74, 111 and 148 kg k/ha alongwith the basal dose of 135 kgN plus 44 kg P/ha. Wheat yield data showed that the application of 37 kg K/ha of potassium chloride was found better in case of rice-wheat and fallow-wheat rotation and 37 kg K/ha of potassium sulfate for maize-wheat rotation. On the average of the three rotations, potassium sulfate at the rate of 74 kg K/ha (90 kg K₂O/ha) was found better and economical. Both the sources were almost equally effective but potassium sulfate out-yielded potassium chloride. Protein content of grains was significantly increased due to K application irrespective of the source and potassium sulfate was found with significantly higher protein content than potassium chloride.     

Voltage-dependent Inwardly Rectifying Potassium Conductance in the Outer Membrane of Neuronal Mitochondria

Potassium fluxes integrate mitochondria into cellular activities, controlling their volume homeostasis and structural integrity in many pathophysiological mechanisms. The outer mitochondrial membrane (OMM) is thought to play a passive role in this process because K⁺ is believed to equilibrate freely between the cytosol and mitochondrial intermembrane space. By patch clamping mitochondria isolated from the central nervous systems of adult mitoCFP transgenic mice, we discovered the existence of I_OMMKi, a novel voltage-dependent inwardly rectifying K⁺ conductance located in the OMM. I_OMMKi is regulated by osmolarity, potentiated by cAMP, and activated at physiological negative potentials, allowing K⁺ to enter the mitochondrial intermembrane space in a controlled regulated fashion. The identification of I_OMMKi in the OMM supports the notion that a membrane potential could exist across this membrane in vivo and suggests that the OMM possesses regulated pathways for K⁺ uptake.     

Oral potassium iodide for the treatment of sporotrichosis

Potassium Iodide is the antimycotic of choice for the treatment of cutaneous sporotrichosis, because of its efficacy, safety and low cost. We carried out a review of published studies on the benefits and adverse reactions of using SSKI (Saturated Solution Potassium Iodide) as treatment for sporotrichosis, but could not identify any well-designed clinical trails. There is an urgent need to conduct randomized double-blind placebo-controlled trials and critically assess usefulness of SSKI by using a standardize monitoring or an effective self-report system.     

Kinetic properties of Kv4.3 and their modulation by KChIP2b

KChIPs are a family of Kv4 K(+) channel ancillary subunits whose effects usually include slowing of inactivation, speeding of recovery from inactivation, and increasing channel surface expression. We compared the effects of the 270 amino acid KChIP2b on Kv4.3 and a Kv4.3 inner pore mutant [V(399, 401)I]. Kv4.3 showed fast inactivation with a bi-exponential time course in which the fast time constant predominated. KChIP2b expressed with wild-type Kv4.3 slowed the fast time constant of inactivation; however, the overall rate of inactivation was faster due to reduction of the contribution of the slow inactivation phase. Introduction of [V(399, 401)I] slowed both time constants of inactivation less than 2-fold. Inactivation was incomplete after 20s pulse durations. Co-expression of KChIP2b with Kv4.3 [V(399, 401)I] slowed inactivation dramatically. KChIP2b increased the rate of recovery from inactivation 7.6-fold in the wild-type channel and 5.7-fold in Kv4.3 [V(399,401)I]. These data suggest that inner pore structure is an important factor in the modulatory effects of KChIP2b on Kv4.3 K(+) channels.     

弱酸（盐）对植物乳杆菌耐酸性的影响

目的探讨弱酸（盐）对植物乳杆菌耐酸性的影响。方法在植物乳杆菌发酵过程中,添加50mmol／L乙酸、10mmol／L丙酸、20mmol／L正丁酸、50mmol／L乙酸钾及2mmol/L柠檬酸钾。结果添加剂量均可使植物乳杆菌耐酸性得到较大的提高,在pH2、37℃下90min,细胞残存率都较对照提高80倍以上,尤以乙酸（盐）、正丁酸为好,而三聚磷酸钾则对细胞耐酸性提高具有较小的作用,细胞残存率较对照约提高5倍。结论在发酵培养基中添加弱酸（乙酸、丙酸及正丁酸）或弱酸盐（乙酸钾、柠檬酸钾及三聚磷酸钾）均可不同程度地提高植物乳扦菌细胞耐酸性。     

Soil beidellite and its relation to problems of potassium fertility and poor response to potassium fertilizers

Summary X-ray diffraction studies were made on soils with and without potassium fertility problems. All soils with clay fractions containing dominant beidellite or vermiculite showed potassium deficiency and lack of response to potassium fertilizer applications. All of the soils containing dominant montmorillonite or other clay minerals contained adequate potassium; on none of these, poor potassium response was reported. Special management practices are needed on the beidellitic and vermiculitic soils to increase potassium and ammonium fertilizer efficiency. Dominance of beidellite in the clay fraction should be reflected in soil classification. Establishment of a ‘beidellite’ family differentiating criterion in the Soil Taxonomy is proposed for this purpose.     

The K+-translocating KdpFABC complex from Escherichia coli: A P-type ATPase with unique features

The prokaryotic KdpFABC complex from the enterobacterium Escherichia coli represents a unique type of P-type ATPase composed of four different subunits, in which a catalytically active P-type ATPase has evolutionary recruited a potassium channel module in order to facilitate ATP-driven potassium transport into the bacterial cell against steep concentration gradients. This unusual composition entails special features with respect to other P-type ATPases, for example the spatial separation of the sites of ATP hydrolysis and substrate transport on two different polypeptides within this multisubunit enzyme complex, which, in turn, leads to an interesting coupling mechanism. As all other P-type ATPases, also the KdpFABC complex cycles between the so-called E1 and E2 states during catalysis, each of which comprises different structural properties together with different binding affinities for both ATP and the transport substrate. Distinct configurations of this transport cycle have recently been visualized in the working enzyme. All typical features of P-type ATPases are attributed to the KdpB subunit, which also comprises strong structural homologies to other P-type ATPase family members. However, the translocation of the transport substrate, potassium, is mediated by the KdpA subunit, which comprises structural as well as functional homologies to MPM-type potassium channels like KcsA from Streptomyces lividans. Subunit KdpC has long been thought to exhibit an FXYD protein-like function in the regulation of KdpFABC activity. However, our latest results are in favor of the notion that KdpC might act as a catalytical chaperone, which cooperatively interacts with the nucleotide to be hydrolyzed and, thus, increases the rather untypical weak nucleotide binding affinity of the KdpB nucleotide binding domain.     

Critical assessment of a proposed model of Shaker

Detailed three-dimensional structures at atomic resolution are essential to understand how voltage-activated K(+) channels function. The X-ray crystallographic structure of the KvAP channel has offered the first view at atomic resolution of the molecular architecture of a voltage-activated K(+) channel. In the crystal, the voltage sensors are bound by monoclonal Fab fragments, which apparently induce a non-native conformation of the tetrameric channel. Thus, despite this significant advance our knowledge of the native conformation of a Kv channel in a membrane remains incomplete. Numerous results from different experimental approaches provide very specific constraints on the structure of K(+) channels in functional conformations. These results can be used to go further in trying to picture the native conformation of voltage-gated K(+) channels. However, the direct translation of all the available information into three-dimensional models is not straightforward and many questions about the structure of voltage-activated K(+) channels are still unanswered. Our aim in this review is to summarize the most important pieces of information currently available and to provide a critical assessment of the model of Shaker recently proposed by Lainé et al.     

Electrostatic state of the cytoplasmic domain influences inactivation at the selectivity filter of the KcsA potassium channel

KcsA is a proton-activated K⁺ channel that is regulated at two gates: an activation gate located in the inner entrance of the pore and an inactivation gate at the selectivity filter. Previously, we revealed that the cytoplasmic domain (CPD) of KcsA senses proton and that electrostatic changes of the CPD influences the opening and closing of the activation gate. However, our previous studies did not reveal the effect of CPD on the inactivation gate because we used a non-inactivating mutant (E71A). In the present study, we used mutants that did not harbor the E71A mutation, and showed that the electrostatic state of the CPD influences the inactivation gate. Three novel CPD mutants were generated in which some negatively charged amino acids were replaced with neutral amino acids. These CPD mutants conducted K⁺, but showed various inactivation properties. Mutants carrying the D149N mutation showed high open probability and slow inactivation, whereas those without the D149N mutation showed low open probability and fast inactivation, similar to wild-type KcsA. In addition, mutants with D149N showed poor K⁺ selectivity, and permitted Na⁺ to flow. These results indicated that electrostatic changes in the CPD by D149N mutation triggered the loss of fast inactivation and changes in the conformation of selectivity filter. Additionally, the loss of fast inactivation induced by D149N was reversed by R153A mutation, suggesting that not only the electrostatic state of D149, but also that of R153 affects inactivation.