Growth characteristic and ion contents of rice callus under the influence of NaCl and hydroxyproline

Calli of salt tolerant (Bhoora rata) and salt susceptible (GR₁₁) rice varieties were cultured on Linsmaeir and Skoog’s medium containing LD₅₀ concentration of NaCl (200 mM) and hydroxyproline (10 mM). Growth rate of callus and Na⁺, K⁺, Cl⁻, Mg⁺², and Ca⁺² contents of the cultured rice tissues were determined at the end of 0, 2, 4 and 6 weeks of incubation. Hydroxyproline resistant calli of both rice varieties when cultured on Linsmaeir and Skoog’s medium containing both NaCl and hydroxyproline showed increased dry weight and enhanced intracellular levels of K⁺, Mg⁺² and Ca⁺². The accumulation of Na⁺ and Cl⁻ ions was less in the hydroxyproline resistant calli.     

Accumulation of inorganic and organic osmolytes and their role in osmotic adjustment in NaCl-stressed vetiver grass seedlings

The accumulation of inorganic and organic osmolytes and their role in osmotic adjustment were investigated in roots and leaves of vetiver grass (Vetiveria zizanioides) seedlings stressed with 100, 200, and 300 mM NaCl for 9 days. The results showed that, although the contents of inorganic (K⁺, Na⁺, Ca²⁺, Mg²⁺, Cl⁻, NO₃⁻, SO₄²⁻ and H₂PO₃⁻)) and organic (soluble sugar, organic acids, and free amino acids) osmolytes all increased with NaCl concentration, the contribution of inorganic ions (mainly Na⁺, K⁺, and Cl⁻) to osmotic adjustment was higher (71.50–80.56% of total) than that of organic solutes (19.43–28.50%). The contribution of inorganic ions increased and that of organic solutes decreased in roots with the enhanced NaCl concentration, whereas the case in leaves was opposite. On the other hand, the osmotic adjustment was only effective for vetiver grass seedlings under moderate saline stress (less than 200 mM NaCl).     

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.     

Paxillus involutus mycorrhiza attenuate NaCl-stress responses in the salt-sensitive hybrid poplar Populus×canescens

In order to characterise the effect of ectomycorrhiza on Na⁺-responses of the salt-sensitive poplar hybrid Populus × canescens, growth and stress responses of Paxillus involutus (strain MAJ) were tested in liquid cultures in the presence of 20 to 500 mM NaCl, and the effects of mycorrhization on mineral nutrient accumulation and oxidative stress were characterised in mycorrhizal and non-mycorrhizal poplar seedlings exposed to 150 mM NaCl. Paxillus involutus was salt tolerant, showing biomass increases in media containing up to 500 mM NaCl after 4 weeks growth. Mycorrhizal mantle formation on poplar roots was not affected by 150 mM NaCl. Whole plant performance was positively affected by the fungus because total biomass was greater and leaves accumulated less Na⁺ than non-mycorrhizal plants. Energy dispersive X-ray microanalysis using transmission electron microscopy analysis of the influence of mycorrhization on the subcellular localisation of Na⁺ and Cl⁻ in roots showed that the hyphal mantle did not diminish salt accumulation in root cell walls, indicating that mycorrhization did not provide a physical barrier against excess salinity. In the absence of salt stress, mycorrhizal poplar roots contained higher Na⁺ and Cl⁻ concentrations than non-mycorrhizal poplar roots. Paxillus involutus hyphae produced H₂O₂ in the mantle but not in the Hartig net or in pure culture. Salt exposure resulted in H₂O₂ formation in cortical cells of both non-mycorrhizal and mycorrhizal poplar and stimulated peroxidase but not superoxide dismutase activities. This shows that mature ectomycorrhiza was unable to suppress salt-induced oxidative stress. Element analyses suggest that improved performance of mycorrhizal poplar under salt stress may result from diminished xylem loading of Na⁺ and increased supply with K⁺.     

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。     

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。     

Response of maize genotypes to salinity stress in relation to osmolytes and metal-ions contents,oxidative stress and antioxidant enzymes activity

Effect of long term soil salinity (control-S₀ and three levels S₁ to S₃) was studied in two maize (Zea mays L.) genotypes, PEHM 3 (comparatively tolerant) and Navjot (susceptible) 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 and calcium contents, and increased the contents of superoxide radical (O₂ ^·−), hydrogen peroxide (H₂O₂), thiobarbituric acid reactive substances (TBARS), proline, glycinebetaine, total soluble sugars, and sodium, and Na⁺/K⁺ and Na⁺/Ca²⁺ ratios in both the genotypes. Contents of zinc, copper, manganese and iron increased up to S₂. Though under S₀ PEHM 3 had higher content of all the metals, Navjot recorded higher content of Zn at all salinity levels and contents of all metal ions at S₂ and S₃. Activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR) increased upto S₂ in both the genotypes, and upto S₃ in PEHM 3 at the two stages. Salinity induced decrease in RWC, Chl, Car, MSI, K⁺ and Ca²⁺ was significantly greater in Navjot, which also recorded higher Na⁺ content and Na⁺/K⁺ and Na⁺/Ca²⁺ ratios than PEHM-3. PEHM-3 recorded higher contents of proline, glycine-betaine, total soluble sugars, K⁺, Ca²⁺, activity of SOD, APX, CAT, GR, and comparatively lower O^{2 ·−}, H₂O₂ and TBARS contents compared to Navjot.     

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。     

Osmotic adjustment and ion balance traits of an alkali resistant halophyte Kochia sieversiana during adaptation to salt and alkali conditions

Kochia sieversiana (Pall.) C. A. M., a naturally alkali-resistant halophyte, was chosen as the test organism for our research. The seedlings of K. sieversiana were treated with varying (0–400 mM) salt stress (1:1 molar ratio of NaCl to Na₂SO₄) and alkali stress (1:1 molar ratio of NaHCO₃ to Na₂CO₃). The concentrations of various solutes in fresh shoots, including Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, SO₄²⁻, NO₃⁻, H₂PO₃⁻, betaine, proline, soluble sugar (SS), and organic acid (OA), were determined. The water content (WC) of the shoots was calculated and the OA components were analyzed. Finally, the osmotic adjustment and ion balance traits in the shoots of K. sieversiana were explored. The results showed that the WC of K. sieversiana remained higher than 6 [g g⁻¹ Dry weight (DW)] even under the highest salt or alkali stress. At salinity levels >240 mM, proline concentrations increased dramatically, with rising salinity. We proposed that this was not a simple response to osmotic stress. The concentrations of Na⁺ and K⁺ all increased with increasing salinity, which implies that there was no competitive inhibition for absorption of either in K. sieversiana. Based on our results, the osmotic adjustment feature of salt stress was similar to that of alkali stress in the shoots of K. sieversiana. The shared essential features were that the shoots maintained a state of high WC, OA, Na⁺, K⁺ and other inorganic ions, accumulated largely in the vacuoles, and betaine, accumulated in cytoplasm. On the other hand, the ionic balance mechanisms under both stresses were different. Under salt stress, K. sieversiana accumulated OA and inorganic ions to maintain the intracellular ionic equilibrium, with close to equal contributions of OA and inorganic ions to anion. However, under alkali stress, OA was the dominant factor in maintaining ionic equilibrium. The contribution of OA to anion was as high as 84.2%, and the contribution of inorganic anions to anion was only 15.8%. We found that the physiological responses of K. sieversiana to salt and alkali stresses were unique, and that mechanisms existed in it that were different from other naturally alkali-resistant gramineous plants, such as Aneurolepidium chinense, Puccinellia tenuiflora. Responsible Editor: John McPherson Cheeseman.     

Acetylsalicylic acid ameliorates negative effects of NaCl or osmotic stress in Solanum stoloniferum in vitro

The role of acetylsalicylic acid (0, 1 and 10 μM) pre-treatment in amelioration of salt and osmotic stress in a wild species of potato (Solanum stoloniferum) was investigated. We compared the effects of iso-osmotic concentrations of polyethylene glycol 6000 (15 %) and NaCl (80 mM) on the physiological responses of this species in explants grown in the liquid Murashige and Skoog medium. Both salt and drought reduced shoot growth parameters, photosynthetic pigment contents and increased lipid peroxidation, electrolyte leakage, H₂O₂ content and lipoxygenase activity. The effect of NaCl was more severe than that of polyethylene glycol. Salinity also increased Na⁺ content and decreased K⁺ content and K⁺/Na⁺ ratio. Under both stresses, the activities of superoxide dismutase, guaiacol peroxidase, ascorbate peroxidase, catalase and glutathione reductase enzymes were increased. Acetylsalicylic acid pre-treatment alleviated the adverse effects of both stresses on all parameters measured.     

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。     

Growth,ion composition,and stomatal conductance of peas exposed to salinity

Availability of irrigation water of appropriate quality is becoming critical in many regions. Excess salt in irrigation water represents a risk for crop yield, crop quality, and soil properties. During the short vegetation period, field peas require high amounts of water, and irrigation is often indispensable for successful production. Steady presence of NaCl (0.1, 0.2, 0.6 or 1.2 g NaCl L⁻¹ in 1/2 strength Hoagland nutrient solution) under semi-controlled conditions reduced growth and resulted in shorter vegetation. Disturbances in the peas’ water regime were provoked by NaCl, as water content in pea tissues was reduced and stomatal density and stomatal diffusive resistance increased in the presence of higher NaCl concentrations. Concentration of Na⁺ increased in all pea tissues with increased NaCl concentration in the nutrient medium. In the presence of NaCl, concentrations of K⁺, Ca²⁺ and P_i increased in roots, stems and leaves, and decreased and in pods and grains. Concentration ratios Na⁺/K⁺, Na⁺/Ca²⁺, K⁺/Ca²⁺ and (Na⁺+K⁺)/Ca²⁺ in various plant parts were affected as well, but magnitudes of changes were variable. Continuous presence of NaCl in concentrations frequently met in irrigation waters significantly reduced pea growth, impaired the water regime, and altered plant chemical composition.     

盐胁迫对3种平欧杂种榛幼苗叶片解剖结构及离子吸收、运输与分配的影响

研究盐胁迫下3个品种平欧杂种榛幼苗叶片解剖结构和离子代谢特征,以揭示盐胁迫响应与适应机制及不同品种的耐盐性差异。以‘达维’、‘辽榛7号’、‘玉坠’2年生压条苗为材料,在盆栽条件下经轻度、中度、重度(分别为50、100、200 mmol/L NaCl)盐胁迫处理,设对照为0,研究幼苗叶片显微解剖结构参数和Na~+、K~+、Cl~-、Ca²⁺含量的变化及其在根、茎、叶中的吸收、运输和分配特征。不同品种平欧杂种榛叶片厚度、上表皮厚度、下表皮厚度、栅栏组织和海绵组织厚度随着盐胁迫程度的增强呈现出先增加后降低的特点,轻度和中度胁迫下各参数显著高于对照。中度盐胁迫显著提高了各品种叶片结构紧密度。盐胁迫导致平欧杂种榛根、茎、叶Na~+和Cl~-含量明显高于对照。盐胁迫下,Na~+和Cl~-在叶中的绝对含量明显高于茎和根,但二者的增幅以根中最大,叶中最小,表明平欧杂种榛根系首先会吸收并截留一定数量的Na~+和Cl~-,然后将其运输至茎和叶中。与对照相比,轻度和中度盐胁迫下根、茎对K~+和Ca²⁺的吸收保持稳定或减少,叶对K~+和Ca²⁺...     

Exogenous application of free polyamines enhance salt tolerance of pistachio (Pistacia vera L.) seedlings

The protective effects of free polyamines (PAs) against salinity stress were investigated for pistachio seedlings (Pistacia vera cv. Badami-Zarand) in a controlled greenhouse. Seedlings were treated with 25, 50, 100 and 150 mM of salts including NaCl, CaCl₂ and MgCl₂. Foliar treatments of putrescine, spermidine (Spd) and spermine (Spm) (0.1 and 1 mM) were applied during the salinity period. Results showed that growth characteristics of pistachio seedlings decreased under salinity stress and the application of PAs efficiently reduced the adverse effects of salt stress. PAs reduced the severe effects of salt stress in pistachio seedlings neither by increasing the activities of peroxidase and ascorbate peroxidase nor by increasing the proline content but by increasing the activities of superoxide dismutase and catalase and decreasing the hydrogen peroxide (H₂O₂) activity. PAs treated seedlings showed a lower Na⁺:K⁺ ratio and Cl^? in leaves suggesting the role of PAs in balancing the ion exchange and better Na⁺:K⁺ discrimination under salt stress condition. These results showed the promising potential use of PAs especially Spm and Spd for reducing the negative effects of salinity stress and improving the growth of pistachio seedlings.     

Salt stress responses of a halophytic grass <Emphasis Type="Italic">Aeluropus lagopoides</Emphasis> and subsequent recovery

To investigate the salt tolerance mechanisms, Aeluropus lagopoides as a halophytic plant was used. Plants were treated with 0, 150, 450, 600, and 750 mM NaCl and harvested at 0, 4, 8, and 10 days after treatment and 1 day and 1 week after recovery. Optimal growth, measured as fresh and dry weights, occurred at 150 mM NaCl, but it was suppressed by 450, 600, and 750 mM NaCl. Recovery significantly increased fresh and dry weights only in 750 mM NaCl-treated plants. Water content was decreased after NaCl treatment and increased after recovery. Na⁺ and proline contents and activity of superoxide dismutase (SOD) were increased after NaCl treatment and decreased after recovery in all treated plants. In contrast, K⁺ content and ascorbate peroxidase activity decreased after NaCl treatment and increased after recovery in all treated plants. Catalase (CAT) was activated only in 750 mM NaCl-treated plants. Total content of soluble protein was slightly changed after NaCl treatment. It was concluded that proline accumulation for osmotic adjustment, SOD activation for O₂^·− scavenging, and CAT activation at the higher level of salt stress to detoxify produced H₂O₂ were main A. lagopoides strategies under salt stress. A. lagopoides salt tolerance was not based on the restriction of Na⁺ uptake.     

Leaf–water relations and ion concentrations of the halophyte <Emphasis Type="Italic">Atriplex hortensis</Emphasis> in response to salinity and water stress

The impact of salinity and water stress was analyzed in the xero-halophyte Atriplex hortensis using two varieties: green orach (A. hortensis var. purpurea) and red orach (A. hortensis var. rubra). A. hortensis L. is a C₃ species well adapted to salt and drought conditions. To collect information on the physiological impact of different salt and water deficit levels on their water stress resistance, plants were exposed for 3 months to solution containing four levels of NaCl or to water stress regimes including four levels of field capacity. Osmotic potential at zero turgor Ψ_s⁰, osmotic potential at full turgor (Ψ_s¹⁰⁰), relative water content (RWC), ion concentration (Na⁺, K⁺, Ca²⁺, Mg²⁺, and Cl⁻), and malondialdehyde (MDA) were determined at the end of the treatment. The salinity and water stress induced a decrease in Ψ_s¹⁰⁰, Ψ_s⁰, and RWC in both varieties, recorded changes being higher in plants of red variety than those of green variety. Both varieties specifically accumulated Na⁺ in response to drought and salt stress, suggesting that this element could play a physiological role in the stress response of this xero-halophyte species. In contrast, the presence of NaCl and water stress induced a decrease in K⁺, Ca²⁺, and Mg²⁺ concentration in both varieties. Salinity clearly induced an increase in Cl^– concentration in all tissues, but water stress had no impact on this parameter. MDA concentration increased in response to water stress and exogenous NaCl. Based on these findings the more drought-tolerant red orach may be grown in water-limiting soils.     

盐胁迫对槲树(Quercus dentata)幼苗离子平衡及其生理生化特性的影响

检测NaCl胁迫对槲树（Quercus dentata）幼苗离子平衡和生理生化特性的影响,为揭示槲树的耐盐机理,其在园林中的推广应用提供参考。以一年生槲树实生苗作为实验材料,经100、200、300 mmol/L的NaCl溶液浇灌处理30 d,测定不同时间的离子含量和生理生化指标变化。结果表明,随NaCl浓度的增加和处理的时间延长,槲树各指标表现出以下规律：（1）根茎叶积累大量Na⁺,引起离子毒害,导致叶片受损,根系Na⁺含量显著高于地上部分,这种补偿作用有助于减轻地上部分受到的损害;（2）各部分K⁺含量降低,根部较茎叶更为显著,导致Na⁺/K⁺明显升高;（3）Ca²⁺由根部向地上部分转运,在叶片中浓度显著增加,有助于建立新的离子稳态;（4）Mg²⁺含量总体上呈降低趋势;（5）叶片含水量逐渐降低,丙二醛含量和相对电导率逐步升高,且在重度胁迫下的变化更显著;（6）轻度盐胁迫下,叶片过氧化物酶（POD）活性无显著变化,而过氧化氢酶（CAT）和超氧化物歧化酶（SOD）活性逐渐升高,在重度胁迫下3种酶活性出现降低;（7）脯氨酸和可溶性糖少量积累,辅助调节渗透平衡。总之,槲树幼苗能够通过调控离子平衡,提升抗氧化酶活性,积累渗透调节物,从而提高耐盐性,抵御200 mmol/L以下的NaCl胁迫。     

Spatial distributions and net deposition rates of mineral elements in the elongating wheat (Triticum aestivum L.) leaf under saline soil conditions

Wheat leaf growth is known to be spatially affected by salinity. The altered spatial distribution of leaf growth under saline conditions may be associated with spatial changes in tissue mineral elements. The objective of this study was to evaluate the spatial distributions of mineral elements and their net deposition rates in the elongating and mature zones of leaf 4 of the main stem of spring wheat (Triticum aestivum L. cv. Lona) during its linear growth phase under saline soil conditions. Plants were grown in an illitic-chloritic silty loam with 0 and 120 mM NaCl. Three days after emergence of leaf 4, sampling was begun at 3 and 13 h into the 16-h light period. Spatial distributions of fresh weight (FW), dry weight (DW), and Na⁺, K⁺, Cl⁻, NO⁻ ₃, Ca²⁺, Mg²⁺, total P, and total N in the elongating and mature tissues were determined on a millimeter scale. The patterns of spatial distribution of Na⁺, Cl⁻, K⁺, NO₃ ⁻, and Ca²⁺ in the growing leaves were affected by salinity, while those of Mg²⁺, total P, and total N were not. Sodium, K⁺, Cl⁻, Ca²⁺, Mg²⁺, and total N concentrations (mmol · kg⁻¹ FW) were consistently higher at 120 mM NaCl than at 0 mM NaCl along the leaf axis from the leaf base, whereas NO₃ ⁻ concentration was lower at 120 mM NaCl. Deposition rates of all nutrients were greatest in the elongation zone. The elongation zone was the strongest sink for mineral elements in the leaf tissues. Local net deposition rates of Na⁺, Cl⁻, Ca²⁺, and Mg²⁺ (mmol · kg⁻¹ FW · h⁻¹) in the most actively elongating zone were enhanced by 120 mM NaCl, whereas for NO₃ ⁻ this was depressed. The lower supply of NO⁻ ₃ to growing leaves may be responsible for the inhibition of growth under saline conditions. Higher tissue concentrations of Na⁺ and Cl⁻ may cause ion imbalance but probably did not result in ion toxicity in the growing leaves. Potassium, Ca²⁺, Mg²⁺, total P, and total N are less plausibly responsible for the reduction in leaf growth in this study. Higher tissue K⁺ and Ca²⁺ concentrations at 120 mM NaCl are probably due to the presence of high Ca²⁺ in the soil of this study. Received: 13 March 1997 / Accepted: 9 June 1997     

Effect of sodium chloride on the response of the halophyte species <Emphasis Type="Italic">Sesuvium portulacastrum</Emphasis> grown in mannitol-induced water stress

Sesuvium portulacastrum is a halophytic species well adapted to salinity and drought. In order to evaluate the physiological impact of salt on water deficit-induced stress response, we cultivated seedlings for 12 days, in the presence or absence of 100 mmol l⁻¹ NaCl, on a nutrient solution containing either 0 mmol l⁻¹ or 25 mmol l⁻¹ mannitol. Mannitol-induced water stress reduced growth, increased the root/shoot ratio, and led to a significant decrease in water potential and leaf relative water content, whereas leaf Na⁺ and K⁺ concentrations remained unchanged. The addition of 100 mmol l⁻¹ NaCl to 25 mmol l⁻¹ mannitol-containing medium mitigated the deleterious impact of water stress on growth of S. portulacastrum, improved the relative water content, induced a significant decrease in leaf water potential and, concomitantly, resulted in enhancement of overall plant photosynthetic activity (i.e. CO₂ net assimilation rate, stomatal conductance). Presence of NaCl in the culture medium, together with mannitol, significantly increased the level of Na⁺ and proline in the leaves, but it had no effect on leaf soluble sugar content. These findings suggest that the ability of NaCl to improve plant performance under mannitol-induced water stress may be due to its effect on osmotic adjustment through Na⁺ and proline accumulation, which is coupled with an improvement in photosynthetic activity. A striking recovery in relative water content and growth of the seedlings was also recorded in the presence of NaCl on release of the water stress induced by mannitol.     

Effects of salt stress on ion content,antioxidant enzymes and protein profile in different tissues of Broussonetia papyrifera

Although some plant responses to salinity have been characterized, the precise mechanisms by which salt stress damages plants are still poorly understood especially in woody plants. In the present study, the physiological and biochemical responses of Broussonetia papyrifera, a tree species of the family, Moraceae, to salinity were studied. In vitro-produced plantlets of B. papyrifera were treated with varying levels of NaCl (0, 50, 100 and 150 mM) in hydroponic culture. Changes in ion contents, accumulation of H₂O₂, as well as the activities and isoform profiles of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in the leaves, stems and roots were investigated. Under salt stress, there was higher Na⁺ accumulation in roots than in stems and leaves, and Ca^2 +, Mg^2 + and P^3 + content, as well as K⁺/Na⁺ ratio were affected. NaCl treatment induced an increase in H₂O₂ contents in the tissues of B. papyrifera. The work demonstrated that activities of antioxidant defense enzymes changed in parallel with the increased H₂O₂ and salinity appeared to be associated with differential regulation of distinct SOD and POD isoenzymes. Moreover, SDS-PAGE analysis of total proteins extracted from leaves and roots of control and NaCl-treated plantlets revealed that in the leaves salt stress was associated with decrease or disappearance of some protein bands, and induction of a new protein band after exposure to 100 and 150 mM NaCl. In contrast, NaCl stress had little effect on the protein pattern in the roots. In summary, these findings may provide insight into the mechanisms of the response of woody plants to salt stress.