NaCl处理对西伯利亚白刺幼苗生长及离子平衡的影响

以1年生西伯利亚白刺水培幼苗为材料,研究了不同浓度NaCl(0、200、400mmol·L~(-1))处理对幼苗生长及不同器官(根、茎、叶)中Na~+、K~+、Ca~(2+)、Mg~(2+)的吸收、运输与分配的影响,探讨西伯利亚白刺的盐适应机制。结果表明:(1)200mmol·L~(-1) NaCl处理促进了西伯利亚白刺幼苗的生长及叶片肉质化程度,400mmol·L-1 NaCl处理显著抑制其生长。(2)随着NaCl处理浓度的升高,西伯利亚白刺幼苗根、茎、叶中Na~+含量显著增加,且叶中Na~+含量显著高于茎和根中;根系中K~+含量显著增加;根、茎、叶中Ca~(2+)、Mg~(2+)含量在200mmol·L~(-1) NaCl处理下保持平稳或上升,而在400mmol·L-1 NaCl处理下显著下降。(3)各器官中K~+/Na~+、Ca~(2+)/Na~+和Mg~(2+)/Na~+比值总体随NaCl处理浓度的升高呈下降趋势,且根部离子比值始终高于叶片和茎。(4)随着NaCl处理浓度的升高,西伯利亚白刺幼苗根-茎SK,Na显著下降,而根-茎SCa,Na、SMg,Na及茎-叶SK,Na、SCa,Na、SMg,Na逐渐提高。研究发现,西伯利亚白刺的盐适应机制主要是通过植株的补偿生长效应及叶片对Na~+的聚积作用实现的,同时也与根系对K~+的扣留及茎叶对K~+、Ca~(2+)、Mg~(2+)选择性运输能力增强有关。     

NaCl胁迫对圆柏幼苗生长和离子吸收及分配的影响

以当年生圆柏幼苗为实验材料,采用温室调控盆栽土培法研究了不同浓度NaCl(0、100、200、300mmol·L-1)胁迫21d对其生长情况及不同器官(根、茎、叶)中K~+、Na~+、Ca~(2+)和Mg~(2+)的吸收和分配的影响,以探讨圆柏幼苗对盐环境的生长适应性及耐盐机制。结果表明:(1)随着NaCl胁迫浓度的增加,圆柏幼苗生长,包括株高、地径、相对生长量以及生物量的积累均呈下降趋势,而其根冠比却增加。(2)在各浓度NaCl胁迫处理下,圆柏幼苗根、茎、叶中Na~+含量较对照均显著增加,而且叶中Na~+含量显著高于茎和根,叶中Na~+含量是根中的5倍。(3)随着NaCl胁迫浓度的升高,圆柏幼苗各器官中K~+、Ca~(2+)和Mg~(2+)含量以及K~+/Na~+、Ca~(2+)/Na~+及Mg~(2+)/Na~+比值均呈下降趋势。(4)在NaCl胁迫条件下,圆柏幼苗根系离子吸收选择性系数SK,Na、SCa,Na、SMg,Na显著提高,茎、叶离子转运选择性系数SCa,Na、SMg,Na则逐渐降低,叶中离子转运选择性系数SK,Na则随着NaCl胁迫浓度的升高显著降低,大量Na~+进入地上部,减缓了盐胁迫对根系的伤害。研究认为,圆柏幼苗的盐适应机制主要是通过根系的补偿生长效应及茎、叶对Na~+的聚积作用来实现的,同时也与根对K~+、Ca~(2+)、Mg~(2+)的选择性运输能力增强和茎、叶稳定的K~+、Ca~(2+)、Mg~(2+)的选择性运输能力有关。     

RETRACTED ARTICLE: Analysis of the physiological mechanism of salt-tolerant transgenic rice carrying a vacuolar Na+/H+ antiporter gene from Suaeda salsa

Salt stress is one of the most serious factors limiting the productivity of agricultural crops. Increasing evidence has demonstrated that vacuolar Na⁺/H⁺ antiporters play a crucial role in plant salt tolerance. In the present study, we expressed the Suaeda salsa vacuolar Na⁺/H⁺ antiporter SsNHX1 in transgenic rice to investigate whether this can increase the salt tolerance of rice, and to study how overexpression of this gene affected other salt-tolerant mechanisms. It was found that transgenic rice plants showed markedly enhanced tolerance to salt stress and to water deprivation compared with non-transgenic controls upon salt stress imposition under outdoor conditions. Measurements of ion levels indicated that K⁺, Ca²⁺ and Mg²⁺ contents were all higher in transgenic plants than in non-transformed controls. Furthermore, shoot V-ATPase hydrolytic activity was dramatically increased in transgenics compared to that of non-transformed controls under salt stress conditions. Physiological analysis also showed that the photosynthetic activity of the transformed plants was higher whereas the same plants had reduced reactive oxygen species generation. In addition, the soluble sugar content increased in the transgenics compared with that in non-transgenics. These results imply that up-regulation of a vacuolar Na⁺/H⁺ antiporter gene in transgenic rice might cause pleiotropic up-regulation of other salt-resistance-related mechanisms to improve salt tolerance.Fengyun Zhao and Zenglan Wang contributed equally to this work.     

Growth rate, water relations and ion accumulation of soybean callus lines differing in salinity tolerance under salinity stress and its subsequent relief

A selected Glycine max (L.) salt-tolerant calluscell line (R100) was significantly more tolerant to salt than a salt-sensitiveline (S100) during exposure to salt stress. Growth (Fresh and Dry weights) ofthe R100 cell line declined significantly at NaCl concentrations greater than 75mM, while growth of the S100 cell line was already impaired at 25mM NaCl. Levels of Na⁺ and Cl^– inthe callus were elevated as the salt concentration increased, whileK⁺, Ca²⁺ and Mg²⁺ levels weremarkedly reduced. The lower s reduction and Na⁺accumulation found in the S100 callus corresponded with the higher callusdehydration during salinity. Calli grown on Miller's basal medium weresupplied with 100 mM NaCl for 12 days and then supplied with mediumwithout NaCl to relieve salinity stress. The Na⁺ andCl^– content decreased in both R100 and S100 cell lines duringthe first 24 h and reached normal levels four days after transferto the normal medium. This lower concentration was maintained until the end ofthe experiment. Concurrently, the K⁺ content andK⁺/Na⁺ ratio increased sharply and reached theirhighest levels within 24 h in both salt-sensitive and salt-tolerantcell lines. These data suggest that the inhibitory effects of salinization ongrowth and accumulation of potentially toxic ions (Na⁺,Cl^–) can be readily reversed when salinity is relieved.     

Screening methods for salinity tolerance: a case study with tetraploid wheat

Fast and effective glasshouse screening techniques that could identify genetic variation in salinity tolerance were tested. The objective was to produce screening techniques for selecting salt-tolerant progeny in breeding programs in which genes for salinity tolerance have been introduced by either conventional breeding or genetic engineering. A set of previously unexplored tetraploid wheat genotypes, from five subspecies of Triticum turgidum, were used in a case study for developing and validating glasshouse screening techniques for selecting for physiologically based traits that confer salinity tolerance. Salinity tolerance was defined as genotypic differences in biomass production in saline versus non-saline conditions over prolonged periods, of 3–4 weeks. Short-term experiments (1 week) measuring either biomass or leaf elongation rates revealed large decreases in growth rate due to the osmotic effect of the salt, but little genotypic differences, although there were genotypic differences in long-term experiments. Specific traits were assessed. Na⁺ exclusion correlated well with salinity tolerance in the durum subspecies, and K⁺/Na⁺ discrimination correlated to a lesser degree. Both traits were environmentally robust, being independent of root temperature and factors that might influence transpiration rates such as light level. In the other four T. turgidum subspecies there was no correlation between salinity tolerance and Na⁺ accumulation or K⁺/Na⁺ discrimination, so other traits were examined. The trait of tolerance of high internal Na⁺ was assessed indirectly, by measuring chlorophyll retention. Five landraces were selected as maintaining green healthy leaves despite high levels of Na⁺ accumulation. Factors affecting field performance of genotypes selected by trait-based techniques are discussed.     

Effect of salinity on chlorophyll and proline contents in three aquatic macrophytes

The role of proline in imparting tolerance to salinity was investigated in Hydrilla verticillata, Najas indica and Najas gramenia. The plants were exposed to different concentrations of NaCl and artificial sea water (SWS) separately. The chlorophyll (Chl) a/b ratio decreased significantly in all the three plant species in both NaCl and SWS treatments, comparatively more in former than the latter. NaCl resulted in drastic decrease in this ratio in salt sensitive H. verticillata and N. indica, but in somewhat lesser decrease in salt resistant N. gramenia. Proline content increased at both NaCl and SWS treatments, especially at the latter. However, in H. verticillata proline content at 1.5 and 2.5 % NaCl decreased. It was concluded that proline cannot be used as a biochemical marker of salt tolerance in aquatic plants, however, the decrease in Chl a/b ratio in response to NaCl may be used as an index of salt sensitivity in this ecological group of plants. This revised version was published online in August 2006 with corrections to the Cover Date.     

Fluorescent labeling of (Na + K)-ATPase by 5-iodoacetamidofluorescein

5-Iodoacetamidofluorescein (5-IAF) covalently labels dog kidney (Na⁺ + K⁺)-ATPase with approximately 2 moles incorporated per mole of enzyme. ATPase and K⁺-phosphatase activities are fully retained after reaction, and the kinetic parameters for Na⁺, K⁺, Mg²⁺, ATP and p-nitrophenyl phosphate are likewise not significantly affected. The fluorescence of the bound 5-IAF is increased by ATP, Na⁺, and Mg²⁺, and decreased by K⁺. These fluorescence changes likely reflect ligand-induced stabilization of the E₁ or E₂ states of the enzyme.     

Sodium,potassium, chloride and proline concentrations of chloroplasts isolated from a halophyte,Mesembryanthemum crystallinum L.

Concentrations of four major solutes (Na⁺, K⁺, Cl^-, proline) were determined in isolated, intact chloroplasts from the halophyte Mesembryanthemum crystallinum L. following long-term exposure of plants to three levels of NaCl salinity in the rooting medium. Chloroplasts were obtained by gentle rupture of leaf protoplasts. There was either no or only small leakage of inorganic ions from the chloroplasts to the medium during three rapidly performed washing steps involving precipitation and re-suspension of chloroplast pellets. Increasing NaCl salinity of the rooting medium resulted in a rise of Na⁺ und Cl^- in the total leaf sap, up to approximately 500 and 400 mM, respectively, for plants grown at 400 mM NaCl. However, chloroplast levels of Na⁺ und Cl^- did not exceed 160–230 and 40–60 mM, respectively, based upon a chloroplast osmotic volume of 20–30 l per mg chlorophyll. At 20 mM NaCl in the rooting medium, the Na⁺/K⁺ ratio of the chloroplasts was about 1; at 400 mM NaCl the ratio was about 5. Growth at 400 mM NaCl led to markedly increased concentrations of proline in the leaf sap (8 mM) compared with the leaf sap of plants grown in culture solution without added NaCl (proline 0.25 mM). Although proline was fivefold more concentrated in the chloroplasts than in the total leaf sap of plants treated with 400 mM NaCl, the overall contribution of proline to the osmotic adjustment of chloroplasts was small. The capacity to limit chloroplast Cl^- concentrations under conditions of high external salinity was in contrast to an apparent affinity of chloroplasts for Cl^- under conditions of low Cl^- availability.Abbreviation Chl chlorophyll     

Osmolytes and metal ions accumulation,oxidative stress and antioxidant enzymes activity as determinants of salinity stress tolerance in maize genotypes

Effect of soil salinity was studied in two maize (Zea mays L.) genotypes, DTP-w-c 9 (comparatively tolerant) and Prabhat (susceptible) under control and three levels of salinity at vegetative and anthesis stages during summer–rainy season. Salinity stress decreased relative water content (RWC), chlorophyll (Chl) and carotenoid (Car) contents, membrane stability index (MSI), potassium (K⁺) and calcium (Ca²⁺) contents, and increased the rate of superoxide radical (O₂^·−) production, contents of hydrogen peroxide (H₂O₂), thiobarbituric acid reactive substances (TBARS) (measure of lipid peroxidation), proline, glycine-betaine, total soluble sugars, sodium (Na⁺), and Na⁺/K⁺ and Na⁺/Ca²⁺ ratios in both the genotypes. Activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR) increased up to S₂ salinity level in both the genotypes, and up to highest salinity level (S₃) in DTP-w-c 9 at the two stages. Salinity-induced decrease in RWC, Chl, Car, MSI, K⁺ and Ca²⁺ was significantly greater in Prabhat, which also recorded higher Na⁺ content and Na⁺/K⁺ and Na⁺/Ca²⁺ ratios than DTP-w-c 9. DTP-w-c 9 recorded higher contents of proline, glycine-betaine, total soluble sugars, K⁺, Ca²⁺, activity of SOD, APX, CAT, GR, and comparatively lower O₂^·−, H₂O₂ and TBARS contents compared to Prabhat. Results show that salinity tolerance of DTP-w-c 9, as manifested by less decrease in RWC, Chl, Car and MSI, is associated with maintenance of adequate levels of K⁺ and Ca²⁺, greater contents of osmolytes, higher antioxidant enzymes activity, and lower O₂^·−, H₂O₂, TBARS and Na⁺ contents than Prabhat.     

Responses of salt-tolerant and intolerant wheat genotypes to sodium chloride: Photosynthesis,antioxidants activities,and yield

Physiological responses of two wheat (Triticum aestivum L.) genotypes (salt-tolerant DK961 and salt-sensitive JN17) to increased salt concentrations (50, 100, 150 mM NaCl: NaCl⁵⁰, NaCl¹⁰⁰, NaCl¹⁵⁰) were studied. Photosynthetic capacity, irradiance response curves, contents of soluble sugars, proteins, and chlorophyll (Chl), K⁺/Na⁺ ratio, and activities of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) in flag leaves were measured on 7 d after anthesis. In control (NaCl⁰) plants, non-significant (p>0.05) differences were found in gas exchange and saturation irradiance (SI) between salt-tolerant (ST) and salt-sensitive (SS) wheat genotypes. However, we found higher soluble sugar and protein contents, K⁺/Na⁺ ratio, and antioxidant enzyme activities, but lower Chl content and yield in ST wheat. Salinity stresses remarkably increased soluble sugar and protein contents and the antioxidant activities, but decreased K⁺/Na⁺ ratio, Chl contents, SI, photosynthetic capacities, and yield, the extent being considerably larger in JN17 than DK961. Although the soluble sugar and protein contents and the antioxidant activities of JN17 elevated more evidently under salt stresses, those variables never reached the high levels of DK961. The antioxidant enzyme activities of SS wheat increased in NaCl⁵⁰ and NaCl¹⁰⁰, but decreased rapidly when the NaCl concentration reached 150 mM. Thus the ST wheat could maintain higher grain yield than the SS one by remaining higher osmoregulation and antioxidative abilities, which led to higher photosynthetic capacity. Hence the ST wheat could harmonize the relationship between CO₂ assimilation (source) and the grain yield (sink) under the experimental conditions.     

Comparative salt tolerance analysis between Arabidopsis thaliana and Thellungiella halophila, with special emphasis on K(+)/Na(+) selectivity and proline accumulation

The eco-physiology of salt tolerance, with an emphasis on K⁺ nutrition and proline accumulation, was investigated in the halophyte Thellungiella halophila and in both wild type and eskimo-1 mutant of the glycophyte Arabidopsis thaliana, which differ in their proline accumulation capacity. Plants cultivated in inert sand were challenged for 3 weeks with up to 500 mM NaCl. Low salinity significantly decreased A. thaliana growth, whereas growth restriction was significant only at salt concentrations equal to or exceeding 300 mM NaCl in T. halophila. Na⁺ content generally increased with the amount of salt added in the culture medium in both species, but T. halophila showed an ability to control Na⁺ accumulation in shoots. The analysis of the relationship between water and Na⁺ contents suggested an apoplastic sodium accumulation in both species; this trait was more pronounced in A. thaliana than in T. halophila. The better NaCl tolerance in the latter was associated with a better K⁺ supply, resulting in higher K⁺/Na⁺ ratios. It was also noteworthy that, despite highly accumulating proline, the A. thaliana eskimo-1 mutant was the most salt-sensitive species. Taken together, our findings indicate that salt tolerance may be partly linked to the plants’ ability to control Na⁺ influx and to ensure appropriate K⁺ nutrition, but is not linked to proline accumulation.     

Salt tolerance in rice in vitro: Implication of accumulation of Na+, K+ and proline

The implication of accumulation of both inorganic (Na⁺, K⁺) and organic (proline) solutes were evaluated in unadapted and NaCl-adapted callus of a salt-sensitive (Basmati 370) and a salt-tolerant (SR-26B) cultivar of rice (Oryza sativa L.) after a NaCl shock. Accumulation of Na⁺,K⁺ and/or proline in callus was co relatable and the relative presence of these components in tissues after shock treatment was found to be important factors to support differential regrowth capacities of the shock treated calluses. Presence or retention of K⁺ in rice callus was a key factor for salt tolerance as it was observed to be positively correlated with growth in both the varieties. The results indicated that K⁺ was the first candidate to counteract the negative water potential of outside milieu, while proline was probably the last metabolic device that rice calluses opted for when exposed to salt stress.     

Salt tolerance inNitellopsis obtusa

Summary The mechanism of salt tolerance was studied using isolated internodal cells of the charophyteNitellopsis obtusa grown in fresh water. When 100 mM NaCl was added to artificial pond water (0.1 mM each of NaCl, KC1, CaCl₂), no cell survived for more than one day. Within the first 30 minutes, membrane potential (E_m) depolarized and membrane resistance (R_m) decreased markedly. Simultaneously, cytoplasmic Na⁺ increased and K⁺ decreased greatly. At steady state the increase in Na⁺ content was roughly equal to the decrease in K⁺ content. The Cl^– content of the cytoplasm did not change. These results suggest that Na⁺ enters the cytoplasm by exchange with cytoplasmic K⁺. Both the entry of Na⁺ and the exit of K⁺ are assumed to be passive and the latter being caused by membrane depolarization. Vacuolar K⁺, Na⁺, and Cl^– remained virtually constant, suggesting that rapid influx of Na⁺ from the cytoplasm did not occur.In 100 mM NaCl containing 10 mM CaCl₂, membrane depolarization, membrane resistance decrease and changes in cytoplasmic [Na⁺] and [K⁺] did not occur, and cells survived for many days. When cells treated with 100 mM NaCl were transferred within 1 hour to 100 mM NaCl containing 10 mM CaCl₂, Em decreased, Rm increased, cytoplasmic Na⁺ and K⁺ returned to their initial levels, and cells survived. Two possible mechanisms for the role of Ca²⁺ in salt tolerance inNitellopsis are discussed; one a reduction in plasmalemma permeability to Na⁺ and the other a stimulation of active Na⁺-extrusion.     

Selection of callus cultures of sugarcane (Saccharum sp.) tolerant to NaCl and their response to salt stress

Stable callus cultures tolerant to NaCl (68 mM) were developed from salt-sensitive sugarcane cultivar CP65-357 by in vitro selection process. The accumulation of both inorganic (Na⁺, Cl⁻ and K⁺) and organic (proline and soluble sugars) solutes was determined in selected and non-selected calli after a NaCl shock in order to evaluate their implication in in vitro salt tolerance of the selected lines. Both salt-tolerant and non-selected calli showed similar relative fresh weight growth in the absence of NaCl. No growth reduction was observed in salt-tolerant calli while a significant reduction about 32% was observed in nonselected ones when both were cultivated on 68 mM NaCl. Accumulation of Na⁺ was similar in both salt-tolerant and non-selected calli in the presence of NaCl. Accumulation of Cl⁻ was lower in NaCl-tolerant than in non-selected calli while proline and soluble sugars were more accumulated in salt-tolerant than in non-selected calli when both were exposed to salt. K⁺ level decreased more severely in non-selected calli than in NaCl-tolerant ones after NaCl shock. The results indicated that K⁺ and Cl⁻ may play a key role in in vitro salt-tolerance in sugarcance cell lines obtained by in vitro selection and that organic solutes could contribute mainly to counteract the negative water potential of the outside medium.     

盐渍土壤大果沙枣树主要矿质阳离子的吸收和分配特征

为探明大果沙枣树体矿质离子渗透调节机制,比较分析了盐渍化生境中1～12a生树的根、枝和叶部主要矿质阳离子的吸收、分配特征。结果表明:(1)大果沙枣树体内Ca~(2+)的积累量最高(13.79 g/kg),K~+次之(5.92 g/kg),Na~+最低(1.00 g/kg);随着树龄的增大,大果沙枣根部的Na~+以及枝和叶部的K~+、Ca~(2+)、Mg~(2+)的积累量均逐渐增大,而根部的K~+含量则逐渐减少;高龄段(10～12a)树体根部的Na~+累积量显著(P0.05)高于中低龄(1～9a)段。(2)大果沙枣树体内K~+/Na~+最大(15.36),Mg~(2+)/Na~+次之(12.25),Ca~(2+)/Na~+最小(10.51),根和枝部的K~+/Na~+均随着树龄的增大而降低,叶部则表现相反。(3)土壤中的K~+和Mg~(2+)向根方向、根部K~+、Mg~(2+)和Ca~(2+)向枝方向以及根部的K~+和Mg~(2+)向叶方向的选择运移系数均随着树龄的增大呈直线上升趋势。(4)土壤中Na~+与根部Na~+含量呈极显著正相关关系(0.687,P0.01),与叶部的K~+含量呈显著正相关(0.605,P0.05);土壤中K~+含量与根部的Na~+、叶部的K~+分别呈显著和极显著正相关(0.544,0.676),与根部的Mg~(2+)呈显著负相关关系(-0.499)。研究发现,大果沙枣树生长过程中主要通过根部对Na~+的聚积作用,以及K~+、Mg~(2+)和Ca~(2+)在枝、叶部的吸收积累来维持植物体离子平衡,以适应盐渍土壤环境。     

短期NaCl胁迫对不同小麦品种幼苗K+吸收和Na+、K+积累的影响

为研究盐胁迫下小麦幼苗生长及Na⁺、K⁺的吸收和积累规律,以中国春、洲元9369和长武134等3种耐盐性不同小麦品种为材料,采用非损伤微测技术检测盐胁迫2 d后的根系K⁺离子流变化,并对植株体内的Na⁺、K⁺含量进行测定。结果表明:短期(2d)盐胁迫对小麦生长有抑制作用,且对根系的抑制大于地上部,耐盐品种下降幅度小于盐敏感品种。盐胁迫下,小麦根际的 K⁺大量外流,盐敏感品种中国春K⁺流速显著高于耐盐品种长武134,最高可达15倍。小麦幼苗地上部分和根系均表现为Na⁺积累增加,K⁺积累减少,Na⁺/K⁺比随盐浓度增加而上升。中国春限Na⁺能力显著低于长武134,Na⁺/K⁺则显著高于长武134。综上所述,盐胁迫下造成小麦组织器官中Na⁺/K⁺比上升的主要原因是根系K⁺大量外流和Na⁺的过量积累,耐盐性不同的小麦品种间差异显著,并认为根系对K⁺的保有能力可能是作物耐盐性评价的一个重要指标。     

Cation co-tolerance phenomenon in cell cultures of Oryza sativa adapted to LiCl and NaCl

Cell lines of Oryza sativa L. (cv. Taipei-309) were adapted to 30 mM LiCl and 150 mM NaCl. Both adapted lines were considerably more tolerant than non adapted line when grown on 200, 250 and 300 mM NaCl and 30 mM LiCl stresses. The tolerance of LiCl-adapted line to NaCl (150 to 300 mM) and the tolerance of NaCl-adapted cells line to LiCl (30 mM) indicated that there was a cross-adaptation towards alkali metals (Na⁺ and Li⁺) not the Cl^–. Na⁺ and K⁺ contents of all lines which increased with increasing medium salinity but to a different degree. The increase in Na⁺ and K⁺ content in NaCl-adapted and non-adapted lines were comparable, while LiCl-adapted line accumulated significantly lower Na⁺and higher K⁺ content. Proline content of all lines increased with the increase in NaCl-stress but the magnitude of increase was much higher in the LiCl-adapted than other lines. The differential response of adapted lines to NaCl stress in accumulating proline and maintaining the ionic contents reveals that adapted lines have evolved different features of adaptation to cope with NaCl stress.     

Photosystem 2-activity and thylakoid membrane polypeptides of <Emphasis Type="Italic">in vitro</Emphasis> cultured chrysanthemum as affected by NaCl

Long-term (30 d) effects of 100, 200, 300, and 400 mM NaCl on photosystem 2 (PS 2)-mediated electron transport activity and content of D1 protein in the thylakoid membranes of chrysanthemum (Dendranthema grandiflorum) cultured in vitro at low irradiance 20 μmol(photon) m⁻² s⁻¹ were investigated. 100 mM NaCl increased contents of chlorophylls (Chl) a and b, carotenoids (Car; xanthophylls + carotenes), and the ratio of Chl a/b, and Car/Chl a+b. However, further increase in NaCl concentration led to the significant reduction in the contents of Chl a, and Chl b, and increase in the ratio of Chl a/b and Car/Chl a+b. NaCl treatment decreased the PS 2-mediated electron transport activity and contents of various thylakoid membrane polypeptides including D1 protein.     

Kinetics of K+-p-Nitrophenyl Phosphatase Stimulation by a Brain Soluble Fraction

We have already described the separation of two brain soluble fractions by Sephadex G-50, one of which stimulates (peak I) and the other inhibits (peak II) Na⁺, K⁺-ATPase and K⁺-p-nitrophenylphosphatase (K⁺-p-NPPase) activities. Here we examine the features of synaptosomal membrane p-NPPase activity in the presence and absence of brain peak I. It was observed that stimulation of Mg²⁺, K⁺-p-NPPase activity by peak I was concentration dependent, The ability of peak I to stimulate p-NPPase activity was lost by heat treatment followed by brief centrifugation. Pure serum albumin also stimulated enzyme activity. K⁺-p-NPPase stimulation by peak I proved dependent on K⁺ concentration but independent of Mg²⁺ and substrate p-nitrophenylphosphate concentrations. Since our determinations were performed in a non-phosphorylating condition reflecting the Na⁺, K⁺-ATPase Na⁺ site, it is suggested that peak I may stimulate the Na⁺-dependent enzyme phosphorylation known to take place from the internal cytoplasmic side.