INFLUENCE OF SODIUM CHLORIDE AND CALCIUM FOLIAR SPRAY ON HYDROPONICALLY GROWN PARSLEY IN NUTRIENT FILM TECHNIQUE SYSTEM

The effects of salinity [30 or 90 mM sodium chloride (NaCl)] and calcium (Ca) foliar application on plant growth were investigated in hydroponically-grown parsley (Petroselinum crispum Mill). Increasing salinity reduced fresh weight and leaf number. Calcium alleviated the negative impacts of 30 mM NaCl on plant biomass and leaf fresh weight but not in case of 90 mM. Plant height, leaf and root dry weight and root length did not differ among treatments. Total phenols increased with calcium application, chlorophyll b reduced by salinity, while total carotenoids increased with salinity and/or Ca application. Salinity reduced nutrient uptake [nitrate (NO₃), potassium (K), phosphorus (P) and Ca] and elemental content in leaves and roots. Calcium application reduced P but increased Ca content in plant tissues. Increments of Na uptake in nutrient solution resulted in higher Na content in leaves and roots regardless Ca application. These findings suggest that calcium treatment may alleviate the negative impacts of salinity.     

Calcium and humic acid affect seed germination,growth, and nutrient content of tomato (Lycopersicon esculentum L.) seedlings under saline soil conditions

The effects of calcium and humic acid on seed germination, growth and macro- and micro-nutrient contents of tomato (Lycopersicon esculentum L.) seedlings in saline soil conditions were evaluated. Different levels of humic acid (0, 500, 1000 and 2000 mg kg^?1) and calcium (0, 100, 200 and 400 mg kg^?1) were applied to growth media treated with 50 mg NaCl kg^?1 before sowing seeds. Seed germination, hypocotyl length, cotyledon width and length, root size, shoot length, leaf number, shoot and root fresh weights, and shoot and root dry weights of the plant seedlings were determined. Macro- and micro-nutrient (N, P, K, Ca, Mg, S, Cu, Fe, Mn and Zn) contents of shoot and root of seedlings were also measured. Humic acid applied to the plant growth medium at 1000 mg kg^?1 concentration increased seedling growth and nutrient contents of plants. Humic acid not only increased macro-nutrient contents, but also enhanced micro-nutrient contents of plant organs. However, high levels of humic acid arrested plant growth or decreased nutrient contents. Levels of 100 and 200 mg kg^?1 Ca²⁺ application significantly increased N, Ca and S contents of shoot, and N and K contents of root.     

Is the salt tolerance of maize related to sodium exclusion? I. Preliminary screening of seven cultivars

Maize (Zea mays L.) plants in the early stage of development were treated with 80 mM sodium chloride (NaCl) with or without supplemental calcium (Ca²⁺) (8.75 mM) for a seven day period. The effects of salinity on dry matter production and shoot and root concentrations of sodium (Na⁺), Ca²⁺, and potassium (K⁺) were measured for seven Pioneer maize cultivars. Salinity significantly reduced total dry weight, leaf area, and shoot and root dry weight below control levels. For all seven cultivars, Na⁺concentrations were reduced and leaf area was significantly increased by supplementing salinized nutrient solutions with 8.75 mM calcium chloride (CaCl₂). The two cultivars with the lowest shoot and root Na⁺ concentrations under NaCl‐salinity showed the greatest increases in total, shoot and root dry weights with the addition of supplemental Ca. Shoot fresh weight/dry weight ratios for all cultivars were decreased significantly by both salinity treatments, but supplemental Ca²⁺ increased the ratio relative to salinity treatments without supplemental Ca. Root fresh weight/dry weight ratios were decreased only by salinity treatments with supplemental Ca. With NaCl‐salinity, cultivars which had lower shoot and root Na⁺ concentrations were found to be more salt sensitive and had significantly lower amounts of dry matter production than those cultivars which had higher shoot and root Na⁺ concentrations. It was concluded that Na⁺ exclusion from the shoot was not correlated with and was an unreliable indicator of salt tolerance for maize.     

Silicon stimulates initial growth and chlorophyll a/b ratio in rice seedlings,and alters the concentrations of Ca,B, and Zn in plant tissues

Abstract

Silicon (Si) is considered a beneficial element for plants due to the far-reaching benefits it confers, including enhanced growth, yield, and crop quality, as well as stress resistance. In this study, we evaluated the effect of Si during germination and initial growth (0.0, 0.5, 1.0, or 1.5?mM Si) and during vegetative growth (0, 1, 2, or 3?mM Si) in rice (Oryza sativa) cv. Morelos A-98. Si did not affect germination but stimulated seedling height, root length, number of roots, as well as fresh and dry biomass weight of shoots and roots during initial growth. During vegetative growth, the application of 3?mM Si significantly increased the chlorophyll a/chlorophyll b ratio, but no major changes were observed either in growth or in concentrations of most nutrients, with the exception of Ca (which increased with 3?mM Si), and B and Zn (which decreased in the presence of Si). In conclusion, applying Si had positive effects during the initial stage of growth, increasing seedling height, root length, root number, and fresh and dry biomass weight. Under our experimental conditions, Si did not affect germination and vegetative growth, but increased Ca concentrations and decreased B and Zn concentrations.     

二氧化碳施肥对番茄幼苗生长与养分吸收利用的影响

Exposing tomato seedlings to elevated CO2 concentrations may have potentially profound impacts on the tomato yield and quality. A growth chamber experiment was designed to estimate how different nutrient concentrations influenced the effect of elevated CO2 on the growth and nutrient uptake of tomato seedlings. Tomato (Hezuo 906) was grown in pots placed in controlled growth chambers and was subjected to ambient or elevated CO2 (360 or 720 μL L-1), and four nutrient solutions of different strengths (1/2-, 1/4-, 1/8-, and 1/16-strength Japan Yamazaki nutrient solutions) in a completely randomized design. The results indicated that some agricultural characteristics of the tomato seedlings such as the plant height, stem thickness, total dry and fresh weights of the leaves, stems and roots, the G value (G value = total plant dry weight/seedling age),and the seedling vigor index (seedling vigor index = stem thickness/(plant height × total plant dry weight) increased with the elevated CO2, and the increases were strongly dependent on the nutrient solution concentrations, being greater with higher nutrient solution concentrations. The elevated CO2 did not alter the ratio of root to shoot. The total N, P, K, and C absorbed from all the solutions except P in the 1/8- and 1/16-strength nutrient solutions increased in the elevated CO2 treatment. These results demonstrate that the nutrient demands of the tomato seedlings increased at elevated CO2 concentrations.     

盐胁迫对诱变小麦种子萌发及幼苗生理特性的影响

本研究以化学诱变获得的小麦突变体为材料,研究了盐胁迫对小麦发芽及幼苗生长的影响。结果表明,随着NaCl浓度(0、100 mmol.L 1、200 mmol.L 1、300 mmol.L 1、400 mmol.L 1)的增加,小麦的发芽率、发芽指数、活力指数、芽长、根长、芽鲜重和干重、根鲜重和干重均呈下降趋势,300 mmol.L 1NaCl为4种小麦(3个突变体、1个对照CAO811CK)发芽能力的临界盐浓度,其中突变体CAO8113K优于其他小麦材料。在300 mmol.L 1NaCl胁迫下,随着时间延长(12 h、24 h、48 h、96 h、192 h),4种小麦材料幼苗可溶性蛋白含量、丙二醛(MDA)含量逐渐增加,超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性呈上升趋势。采用模糊数学隶属函数法对可溶性蛋白、MDA、SOD、POD、CAT 5项生理指标进行综合评价,4种小麦材料耐盐潜力由强到弱依次为CAO8113K>CAO811CK>CAO8114K>CAO8112K,CAO8113K突变体小麦材料表现出较强抗盐性,与发芽指标检测结果基本一致。     

Responses of barley to hypoxia and salinity during seed germination,nutrient uptake,and early plant growth in solution culture

The resistance of most plants to salt can be impaired by concurrent waterlogging. However, few studies have examined this interaction during germination and early seedling growth and its implications for nutrient uptake. The aim of the study was to examine the response of germination, early growth, and nutrient uptake to salt (NaCl) and hypoxia applied to barley (Hordeum vulgare L. cv. Stirling), in solution culture. Hypoxia, induced by covering seeds with water, lowered the germination from 94% to 28% but salinity and hypoxia together lowered it further to 13% at 120 mM NaCl. While the germination was 75% at 250 mM NaCl in aerated solution, it was completely inhibited at this NaCl concentration under hypoxia. Sodium ion (Na⁺) concentrations in germinated seedlings increased with increasing salinity under both aerated and hypoxic conditions during germination, while K⁺ and Mg⁺ concentrations were decreased with increasing salinity in 6 d old seedlings. After 20 d, control seedlings had the same dry weights of the roots and shoots with and without hypoxia but at 10 mM NaCl and higher, shoot and root dry weight was depressed with hypoxia. Sodium ion increased in roots and shoots with increased NaCl under both aerated and hypoxic conditions while K⁺ was depressed when salinity and hypoxia were applied together and Ca²⁺ was mostly decreased by NaCl. In general, hypoxia had greater effects on nutrient concentrations than NaCl by decreasing N, P, S, Mg, Mn, Zn, and Fe in shoots and by increasing B concentrations. The threshold salinity levels decreased markedly for germination, uptake of a range of nutrients, and for seedling growth of barley under hypoxic compared to well‐aerated conditions.     

温度和CO2浓度升高对水稻幼苗的综合影响

通过人工气候箱模拟中国南方稻区湖北荆州地区大气CO2浓度和温度同时升高的3种气候情景,即在背景温度为24～29℃的人工气候箱中设置以CO2浓度为400molmol?1、升温0℃为对照（CK）,以550molmol?1、升温2℃为中强度处理（M）,以700molmol?1、升温4℃为高强度处理（H）,将催芽后的稻种于各气候箱中处理10d,观测水稻种子萌发和幼苗生理特性的变化。结果表明,（1）水稻幼苗苗高、根长、根数（根长大于1cm）、根苗干重及活力指数均随着CO2浓度和温度的同时升高而上升,其中H处理下幼苗苗高比CK长5.78cm,根长比CK高12.91%,根苗干重为CK的2.6倍,活力指数为CK的3.1倍,种子发芽率、发芽势和发芽指数表现为M处理最高;（2）随着CO2浓度和温度同时升高,稻苗丙二醛（MDA）含量和可溶性糖（SS）逐渐降低,脯氨酸（Pro）含量先增加后减小,可溶性蛋白（SP）含量和过氧化氢酶（CAT）逐渐升高。说明在目前温度和CO2浓度条件下未来升温2～4℃同时CO2浓度增至550molmol?1和700molmol?1对湖北荆州稻区水稻种子萌发和幼苗生长不会产生明显不利影响,但此生长期稻苗营养元素累积受到制约。     

Effects of fractions of coal-derived humic substances on seed germination and growth of seedlings (Lactuga sativa and Lycopersicum esculentum)

Summary Lettuce and tomato seeds were treated in Petri dishes with a humic acid derived from an oxidized coal and with fractions of the same humic acid obtained by ultrafiltration through membranes of known molecular cutoff and by extracting with buffers set at pH 4 and pH 5. The unfractionated humic acid was applied at 40, 100, 1000, and 5000 mg l^-1 whereas the humic fractions were applied at 40, 100, and 200 mg l^-1. Germination parameters such as the number of total germinated seeds, the velocity of seed germination, the fresh weight and dry weight of total seedlings were measured and related to the chemical and physicochemical properties of the humic material. No increase in the germination percentage or the germination rate was observed for either lettuce or tomato seeds. The fresh weight of total seedlings and per seedling increased in treatments with unfractionated humic acid with increasing concentrations for both lettuce and tomato plants without showing signs of growth inhibition up to 5000 mg l^-1. This was attributed to cell elongation and more efficient water uptake. For the lettuce, the fresh weight both of total seedlings and per seedling was enhanced by treating the seeds with fractions of low molecular weight and high content of acidic functions, whereas the dry weight both of total seedlings and per seedling did not change with the humic fraction used. For the tomato seeds in contrast, the dry weight both of total seedlings and per seedling was increased by the use of unfractionated humic acid and by some of the humic fractions. An uptake of humic material by growing tomato seedlings was inferred.     

Irrigation with salt water affects growth,yield, fruit quality,storability and marker-gene expression in cherry tomato

The use of saline water for plant production will become increasingly necessary over future decades. In some cases, fruit quality such as in tomato, can be improved by irrigation with saline water. The influence of different salt concentrations on physiological responses and the expression of some selected genes of cherry tomato (Solanum lycopersicum L), cv. West Virginia 106, was examined. Tomato plants were grown in peatmoss substrate and irrigated with 0, 25, 50, 75, 100 or 150?mM sodium chloride (NaCl) in a glasshouse. The NaCl treatments of 75, 100 and 150?mM salt resulted in shorter plants, decreased stem width, a lower plant dry weight, fewer flowers, and smaller leaf area, while yield was reduced by treatment with concentrations of 50?mM NaCl and above. Average fruit weight and fruit number were also negatively affected by treatment with 50?mM salt and above. Salinity treatment led to increased fruit total soluble solids, titratable acidity and firmness and improved the taste index. Salt-responsive marker genes identified in Moneymaker were also induced in cherry tomato but not at the highest salt concentrations. Our results indicated that cherry tomato treated with 25?mM NaCl produced fruit with improved quality in comparison with non-salinized control plants without compromising yield, while at 50 and 75?mM the improved fruit quality was accompanied by a reduction in yield.     

Silicon priming benefits germination,ion balance,and root structure in salt-stressed durum wheat (Triticum durum desf.)

Abstract

Effects of silicon (Si) priming at 0, 0.5, 1.0, and 1.5?mM on germination, ion balance, and root structure of two durum wheat cultivars at 0, 100, and 200?mM sodium chloride (NaCl) was conducted in a laboratory. An aliquot of 200?mM NaCl with 1.5?mM Si improved Behrang cultivar germination from 54 to 88%, but in Yavaros only from 49 to 85%. In Behrang, the control root length at 200?mM NaCl increased from 5.07 to 7.11?mm when treated with 1.5?mM Si, but Yavaros only increased from 3.18 to 4.09?mm. Behrang accumulated less sodium (Na⁺) and more potassium (K⁺). For mean diameter of central and peripheral metaxylem cells, Behrang benefitted more from Si amelioration than Yavaros. Salinity affected the diameter of central and peripheral metaxylem cells to a greater degree compared to vessel number. Si soil application (1.0 and 1.5?mM Si) may help to establish durum wheat seeds grown under saline conditions.     

Implications of Calcium Nutrition on the Response of Salvadora persica (Salvadoraceae) to Soil Salinity

Effects of Ca (Ca²⁺) level on the response of germination and seedling growth of Salvadora persica Linn. (Salvadoraceae) to sodium chloride (NaCl) salinity in soil were investigated. Salinity significantly retarded the seed germination and seedling growth, but the injurious effects of NaCl on seed germination were ameliorated and seedling growth was restored with Ca supply at the critical level to salinized soil. Calcium supply above the critical level further retarded the seed germination and seedling growth because of the increased soil salinity. Salt stress reduced nitrogen, phosphorus, potassium, and Ca content in plant tissues, but these nutrients were restored by addition of Ca at the critical level to saline soil. The opposite was true for sodium (Na⁺). The results are discussed in terms of the beneficial effects of Ca for plant growth under saline conditions.     

磁化等离子体处理大豆种子的生物学效应

利用不同剂量的磁化等离子体处理晋豆20种子,分析被处理种子发芽率、幼苗生长、呼吸与能量的代谢以及同功酶谱的变化,为探讨磁化等离子体对种子的作用机理提供依据。结果表明,经不同剂量磁化等离子体处理后,种子的发芽率和幼苗的根长、干重没有显著变化;2.0～3.0A处理组苗高、鲜重比对照分别增加17.8%～26.9%和12.70%～17.08%;2.0A处理侧根数比对照显著增加,增幅为11.8%。当处理剂量为2.5A时,根系活力提高60.9%,叶片和根系的呼吸速率分别提高43.68%和38.92%,ATP含量分别提高37.79%和47.68%。磁化等离子体处理大豆种子后幼苗同工酶谱没有特异性条带的产生,但POD和酯酶同工酶的活性得到了普遍提高,其中2.5A处理后POD活性最高。综合分析指标表明2.5A的磁化等离子体处理对刺激种子活力、促进种子发芽和幼苗生长效果最佳。     

Zinc priming promotes seed germination and seedling vigor of rice

The present study evaluated effects of seed zinc (Zn) priming at concentrations from 0 to 25 mM ZnSO₄ on seedling vigor and viability in rice (Oryza sativa L.). Zinc priming substantially increased Zn concentration in the husk, but not in brown rice. The movement of primed Zn from the husk into the inner layers of rice seed during germination was suggested by Zn concentration declining in the husk coinciding with the increase in brown rice over time (r = –0.62; p < 1%), which did not happen in unprimed seed. Zinc priming significantly enhanced seedling growth and development up to 5 mM. Germination rate, root number, and dry weight were much higher than in unprimed seed, but higher Zn concentrations (10 and 25 mM) depressed seedling vigor. Priming rice seed with 2.5 mM Zn also improved the germination rate of rice in a Zn‐deficient soil, with or without soil Zn application. The results confirm that priming rice seed with Zn can improve germination and seedling vigor and for the first time show how Zn requirement of germinating rice seed and seedlings can be met by the prime Zn accumulated in the husk.     

Effect of salicylic acid and salt on wheat seed germination

Abstract

The effects of pretreatment with salicylic acid on wheat seed germination (Triticum aestivum L. cv. Roshan), lipid peroxidation, and superoxide dismutase, catalase, polyphenol oxidase, and peroxidase activity were studied under conditions of salt stress. Seeds treated with different concentrations of salicylic acid were used for measuring germination traits. Salt stress was induced by sodium chloride solution. Seeds were soaked in salicylic acid solution for 24 h, dried with sterile paper, transferred to sterile Petri dishes, and treated with 10 ml NaCl solution at different concentrations. After 1 week, the number of germinated seeds, root length, seedling length, and dry weight were recorded. Antioxidant enzyme activity and lipid peroxidation were also assayed. Salinity decreased seed germination. Thus, a high concentration of NaCl (200 mM) decreased germination by 17.6% compared with control treatment. Salicylic acid significantly increased germination in stressed and control seeds. Salicylic acid increased the level of cell division of seedlings and roots, which increased plant growth. Salt stress significantly increased the activity of the antioxidative enzymes catalase, superoxide dismutase, peroxidase, and polyphenol oxidase in wheat seedlings, and salicylic acid reduced the activity of antioxidant enzymes as stress signal molecules. Our results indicated that scavenging of reactive oxygen species was effective, especially by salicylic acid, and that membrane damage was limited. The aim of the present work was to study the character of changes in enzymatic systems induced by NaCl and salicylic acid in wheat seedlings under conditions of salt stress. In brief, salicylic acid treatment reduced the damaging action of salinity on embryo growth and accelerated a restoration of growth processes; thereupon it may be effective for the improvement of seed germination in arid and semi-arid regions.     

纳米氧化镁促进番茄植株生长的机理

  【目的】  探讨具有抗菌作用剂量的纳米氧化镁 (MgONPs) 对番茄早期生长发育的影响,并明确其被吸收和在植株体内的运输特性,为MgONPs在植物营养和病害防控领域的应用提供理论依据。  【方法】  以番茄为模式植物,利用MgONPs (50～250 μg/mL) 处理番茄种子和幼苗,测定种子萌发率、MgONPs处理幼苗30天后的植株生物量、植物组织细胞形态、叶绿素含量和相对含水量等指标,并用电感耦合等离子发射光谱仪和透射电子显微镜 (TEM) 测定植株对MgONPs的吸收状况。  【结果】  50～250 μg/mL的MgONPs对番茄种子的发芽无抑制作用,而对番茄幼苗生长具有显著的促进作用,其中250 μg/mL剂量作用最显著;此剂量处理后的番茄根长、根干重、地上部分干重和径围分别为20.33 cm、0.11 g、0.20 g、1.65 cm,对照分别为15.63 cm、0.03 g、0.15 g和1.16 cm;番茄叶绿素含量提高了47.37%,相对含水量提高了13.14%。且MgONPs促进了镁元素的吸收,MgONPs处理后番茄叶片中的镁含量较清水组提高了35.16%;透射电子显微镜 (TEM) 照片发现,MgONPs处理后叶片叶绿体周围有纳米颗粒的聚集;扫描电子显微镜 (SEM) 照片和石蜡切片观察证实,MgONPs未破坏番茄植株的组织和细胞形态,明确了在一定浓度下MgONPs对番茄植物细胞无毒副影响。  【结论】  MgONPs在土壤中的分散程度虽然不如在去离子水中,但是依然表现出对番茄生长的显著促进作用,且对种子发芽和幼苗生长无任何不利影响。施入土壤后,MgONPs能被番茄根系吸收,通过维管束系统向上运输至叶片中,从而显著增加叶绿素含量和相对含水量,最终促进了幼苗的生长和干物质积累。在本试验条件下,高浓度 (250 μg/mL) 的MgONPs促进番茄生长的效果好于低浓度。     

Effects of salinity stress on growth indices,physiological parameters and element concentration in Banebaghi (Pistacia sp.) as rootstock for pistachio

Banebaghi is considered a natural hybrid in Pistacia genus that can be used as rootstock for pistachio. In order to study the effects of salinity stress on growth indices, physiological parameters and element concentration in Banebaghi, an experiment was arranged as a factorial in completely randomized design (CRD). Factors were salinity of irrigation water (0, 60 and 120 mM of sodium chloride, calcium chloride, magnesium chloride, respectively), growth type (mutica growth type and pistachio growth type) and stem height (stem height lower half of the plant and stem height upper half of the plant) with four replications. Our results showed that salinity reduced vegetative parameters, SPAD index, leaf relative water content (RWC) and water use efficiency (WUE). Shoot dry weight of seedlings in both heights, decreased at the salinity level of 120 mM, at about 60% compared with control. At the highest level of salinity (120 mM), seedlings with a height lower half of the plant had lower reduction in the fresh and dry weight of the root and showed more resistance to the salinity stress because of maintaining RWC of leaves and high levels of potassium and calcium in the shoot. Salinity increased sodium (Na) concentration of shoot and root in both growth types: mutica and pistachio. Seedlings with pistachio growth type and a height upper half of the plant and seedlings with mutica growth type and a height lower half of the plant had more resistance to salinity stress.     

Effect of Foliar Salicylic Acid Applications on Growth,Chlorophyll, and Mineral Content of Cucumber Grown Under Salt Stress

The objective of this study was to determine the effect of foliar salicylic acid (SA) applications on growth, chlorophyll, and mineral content of cucumber grown under salt stress. The study was conducted in pot experiments under greenhouse conditions. Cucumber seedlings were treated with foliar SA applications at different concentrations (0.0, 0.25, 0.50, and 1.00 mM). Salinity treatments were established by adding 0, 60, and 120 mM of sodium chloride (NaCl) to a base complete nutrient solution. The SA was applied with spraying two times as before and after transplanting. Salt stress negatively affected the growth, chlorophyll content and mineral uptake of cucumber plants. However, foliar applications of SA resulted in greater shoot fresh weight, shoot dry weight, root fresh weight, and root dry weight as well as higher plants under salt stress. Shoot diameter and leaf number per plant increased with SA treatments under salt stress. The greatest chlorophyll content was obtained with 1.00 mM SA treatment in both saline and non-saline conditions. Leaf water relative content (LWRC) reduced in response to salt stress while SA raised LWRC of salt stressed cucumber plants. Salinity treatments induced significant increases in electrolyte leakage. Plants treated with foliar SA had lower values of electrolyte leakage than non-treated ones. In regard to nutrient content, it can be interfered that foliar SA applications increased almost all nutrient content in leaves and roots of cucumber plants under salt stress. Generally, the greatest values were obtained from 1.00 mM SA application. Based on these findings, the SA treatments may help alleviate the negative effect of salinity on the growth of cucumber.     

Growth Responses and Nitrogen-15 Absorption of Desert Saltgrass Under Salt Stress

Abstract

Saltgrass [Distichlis spicata (L.) Greene var. stricta (Gray) Beetle], accession WA-12, collected from a salt playa in Wilcox, AZ, was studied in a greenhouse to evaluate its growth responses in terms of shoot and root lengths, shoot dry-matter yield, and nitrogen (N) (regular and ¹⁵N) absorption rates under control and salt (sodium chloride, NaCl) stress conditions. Plants were grown under a control (no salt) and three levels of salt stress (100, 200, and 400 mM NaCl, equivalent to 5850, 11700, and 23400 mg L^{? 1} sodium chloride, respectively), using Hoagland solution in a hydroponics system. Ammonium sulfate [(¹⁵NH₄)₂SO₄], 53% ¹⁵N (atom percent ¹⁵N) was used to enrich the plants. Plant shoots were harvested weekly, oven-dried at 60°C, and the dry weights measured. At each harvest, both shoot and root lengths were also measured. During the last harvest, plant roots were also harvested and oven-dried, and dry weights were determined and recorded. All harvested plant materials were analyzed for total N and ¹⁵N. The results showed that shoot and root lengths decreased under increasing salinity levels. However, both shoot fresh and dry weights significantly increased at 200 mM NaCl salinity relative to the control or to the 400 mM NaCl level. Shoot succulence (fresh weight/dry weight) also increased from the control (no salt) to 200 mM NaCl, then declined. The root dry weights at both 200 mM and 400 mM NaCl salinity levels were significantly higher than under the control. Concentrations of both total-N and ¹⁵N in the shoots were higher in NaCl-treated plants relative to those under the control. Shoot total-N and ¹⁵N contents were highest in 200 mM NaCl-treated plants relative to those under the control and 400 mM salinity.     

Salt tolerance of Elaeagnus macrophylla and Frankia Ema1 strain isolated from the root nodules of E. macrophylla

Effects of NaCl on the seed germination and growth of Elaeagnus macrophylla seedlings and multiplication of Frankia Ema1 strain isolated from the root nodules of E. macrophylla were examined. The germination rate of seeds was not reduced by N aCI at 50 mM, but was reduced with further increase of the concentration, and germination did not occur at 200 mM NaCl. Root nodules were formed in the seedlings treated with 100 mM NaCl. The fresh and dry weight of the seedlings slightly decreased by the increase of the concentration of NaCl and the rate of decrease was 10–20% at NaCl concentrations higher than 100 mM. However, Na+ concentrations in the shoot increased up to 300 mM by treatment with N aCI at a concentration above 50 mM for 30 d and in some plants the lower leaves fell. The growth of free-living Frankia was markedly suppressed and the hyphae became thick and short in the solution at 100 mM NaCl. This trend was more obvious at 200 mM NaCl. Na⁺ concentration in the cells in the medium with 200 mM NaCl was lower than 20 mM and the cells underwent multiplication again when they were transferred to the medium which did not contain N aCl. These results indicate that the salt tolerance of E. macrophylla seedlings was not very high and the threshold for NaCl ranged between 50 and 100 mM, whereas Frankia Ema1 strain was able to survive in a much higher salt environment.