Effect of salinity on growth,photosynthesis and mineral composition in leguminous plant Alhagi pseudoalhagi (Bieb.)

Leguminous plant Alhagi pseudoalhagi was subjected to 0 (control), 50, 100, and 200 mM NaCI treatments during a 30 d period to examine the mechanism of tolerance to salinity. Plant dry weight, net CO₂ assimilation rate, leaf stomatal conductance, intercellular CO₂ concentration, and solute concentration in leaves, stems, and roots were determined. Total plant weight in the 50 mM treatment was 170% of that of the control after 10 d of treatment. Total plant weight was lower in the 100 and 200 mM treatments than in the control. The leaf CO₂ assimilation rate was approximately 150% of that of the control in the 50 mM treatment, but was not affected significantly by 100 mM of NaCI, while it was reduced to about 60% of that the control in the 200 mM treatment. Similarly stomatal conductance was consistent with the CO₂ assimilation rate regardless of the treatments. Intercellular CO₂ concentration was lower in the NaCI-treated plants than in the control. Changes in CO₂ assimilation rate due to salinity stress could be mainly associated with stomatal conductance and the carboxylation activity. Although the leaf Na⁺ concentration increased to 900 mmol kg^-1 dry weight in the 200 mM treatment compared to 20 mmol kg^-1 in the control, the plants did not die and continued to grow at such a high leaf Na⁺ concentration. Uptake and transportation rates of Na+, Ca²⁺, Mg²⁺, and K⁺, and the accumulation of N were promoted by 50 mM NaCI. Na⁺ uptake rate continued to increase in response to external NaCI concentration. However, the uptake and transportation rates of Ca²⁺, Mg²⁺, and K⁺ behaved differently under 100 and 200 mM salt stress. The results suggest that A. pseudoalhagi is markedly tolerant to salinity due mainly to its photosynthetic activity rather than to other physiological characteristics.     

Characterization of salt tolerance in tomato plant in terms of photosynthesis and water relations

Three commercial tomato cultivars (UC-97, Momotaro, and Edkawi) were subjected to a gradual increase of NaCI concentrations and the effect on biomass production and its parameters was compared. The data indicated that salinity reduced plant growth and the reduction was more pronounced in UC-97 and less in Edkawi. The apparent photosynthetic rate (P _o) was also depressed by the salt treatment and the depression was more remarkable in UC-97 and less in Edkawi. Edkawi shoot showed a much higher concentration of sodium ion and proline compared with the other cultivars, which may result in the maintenance of a higher turgor potential. In all the cultivars examined the stem diameter decreased after the beginning of exposure to light and recovered after the light was turned off. The decrease in the stem diameter during day light was enhanced and the recovery at night decreased after 1 d of salt treatment and the changes in the stem diameter were less conspicuous in Edkawi than in the other cultivars. These results suggest that Edkawi is more tolerant to salinity than the other cultivars due to a higher ability of maintaining the root function for the uptake and supply of water to shoot under salinity conditions but not due to the adjustment of transpiration from stomata.     

Effect of salt stress on photosynthesis and related physiological characteristics of Lycium ruthenicum Murr

Halophytes could withstand the hyper-salinity soil and survive widely in areas where soil salt content is high because they can endure salt stress to a certain extent. Lycium ruthenicum Murr (LRM), with significant nutritional and medicinal values, is one of the most important native halophytes in the arid oasis-desert transition zone of northwestern China. In recent years, artificially planting LRM has been being popular since it can improve saline-alkalized soil and increase the income of local farmers as well. More efforts about the artificial planting of LRM are put in enhancing the productivity and quality, but survivorship of LRM seedling by appropriate saline irrigation is still unclear in arid areas. A field experiment was conducted to explore the responses of LRM to four levels of saline water irrigation (Ec of irrigation water: 2.00?μs?cm^?1 (T₁), 4.51?μs?cm^?1 (T₂), 6.89?μs?cm^?1 (T₃), and 9.00?μs?cm^?1 (T₄)) during the growing seasons in 2014 and 2015. The average soil electrical conductivity (Ec_a) in 0–60 cm depth increased while the biomass of LRM decreased with increasing Ec of irrigation water, and the differences of Ec_a among treatments decreased with increasing salinity level. In contrast to previous research findings, salt stress had more significant effect on photosynthesis and chlorophyll fluorescence of LRM, in which great changes were caused by a threshold following the increased salinity. Most of the light energy absorbed by LRM was used for photosynthesis and heat dissipation when soil salinity was low, what was used for chlorophyll fluorescence when soil salinity was high. The results of the experiment indicate that T₂ was the most suitable irrigation method for artificially planting LRM in the field, and it’s the key to save freshwater resources in arid areas and improve the production of saline-alkali land.     

Influence of seed nitrogen content and biofertilizer priming on wheat germination in salinity stress conditions

In order to study the effects of seed nitrogen content and biofertilizer priming on germination indices of wheat seeds under salinity stress, a factorial experiment based on a completely randomized design with four replications was conducted in 2009. Experimental factors consisted of: (1) the application of different nitrogen fertilizer rates (0, 55, 110 and 165 kg ha^?1 N) on parent plants; (2) priming of achieved seeds by biofertilizers (Nitragin, Biophosphorus and distilled water); and (3) different levels of salinity produced by NaCl (0, ?0.4, ?0.8 and ?1.2 MPa). Germination percentage, germination rate, mean germination time, germination index, radicle and plumule length, radicle and plumule dry weight and radicle number per seedling were measured. Nitrogen application increased seed nitrogen content in parent plants. All germination indices decreased with increasing in salinity levels. Biofertilizer priming, especially Nitragin, had a positive effect on germination percentage, radicle number and radicle and plumule length in most salinity levels. The highest values for germination factors were related to achieved seeds from parent plants that were treated with 110 kg ha^?1 N. Overall, application of middle levels of N fertilizer (55 and 110 kg ha^?1 N) on parent plants combined with seed priming with Nitragin biofertilizer improved the germination indices of wheat under salinity stress.     

Effects of vermicompost and salinity stress on growth and physiological traits of Medicago rigidula L.

The use of vermicompost as a biological fertilizer under salinity stress conditions was tested in this research. Accordingly, the seeds of Medicago rigidula were grown in the greenhouse. The experiment was performed based on factorial arrangement in a completely randomized design using 5 replications. Application rates of vermicompost were 0, 10, 20 and 30%. Salinity stress was conducted in three levels (0, 50 and 100 mM sodium chloride (NaCl)). The highest and the lowest values of the plant survival capacity (%), shoot dry weight (g), leaf relative water content (LRWC) (%), total chlorophyll content (%), leaf area (cm²), total nitrogen content (TNC) (%) and potassium (K) content (%) of the plant tissues were found in VC4 × SL1 and VC1 × SL3 treatments, respectively. Whereas, the maximum and minimum values of root dry weight and root:shoot ratio were seen in VC1 × SL3 and VC4 × SL1 treatments, respectively.     

盐分胁迫对林木种子发芽率的影响研究

试验研究盐分胁迫对林木种子发芽率的影响结果表明 ,NaCl和NaCl KCl 2种盐分对林木种子发芽率和苗木生长均有一定抑制作用 ;随盐分浓度的提高而发芽率逐渐下降 ,幼苗生长呈相同趋势。与复合盐分相比 ,单一盐分对种子发芽和苗木生长抑制作用更强 ,表明K 可一定程度缓解Na 的危害 ,并提出耐盐指数概念     

土壤含水率和含盐量对盐渍土甲烷吸收能力的影响

甲烷（CH4）是一种强效温室气体,准确认识特定类型土壤CH4源汇特征及影响因子调控作用,对于提升土壤CH4吸收潜力以减缓全球气候变化具有重要意义。该研究以盐渍土为研究对象,在土壤室内培养试验中,设置了3个土壤含水率处理,分别为田间持水率（Field Capacity,FC）的50%（50%FC）,75% FC和100% FC,并在每个含水率下设置了6个含盐量处理,电导率分别为0.3、1.0、2.0、3.2、4.9和6.2 dS/m,研究不同土壤含水率和含盐量条件下盐渍土CH4吸收特征。在田间测坑试验中,观测了0.3、1.0和5.0 dS/m 3种含盐量土壤的CH4吸收特征及其对水分动态的响应。室内土壤培养试验结果表明,100%FC下6种盐分水平土壤CH4累积吸收量分别是75%FC下的1.08～1.39倍和50%FC的1.27～1.72倍,表明在田间持水率范围内,含水率升高促进了土壤CH4吸收;在3种含水率下,土壤CH4累积吸收量均随着处理含盐量升高而降低,6.2 dS/m最高含盐量处理的CH4累积吸收量相比0.3 dS/m最低含盐量处理显著降低了42.6%、52.3%和55.1%（P<0.05）;相比50%FC,100%FC含水率下高含盐量对土壤CH4吸收具有更强的抑制作用,土壤含水率和含盐量对CH4吸收的影响存在显著的交互作用。田间测坑试验在野外田间条件下进一步验证了室内培养试验的结果,试验观测期内所有含盐量处理土壤CH4吸收速率均与土壤含水率呈显著正相关关系（P<0.01）;1.0和5.0 dS/m含盐量处理的累积CH4吸收量分别为0.3 dS/m非盐渍土处理的82.6%和59.8%,高含盐量抑制了土壤对CH4的吸收。研究结果表明盐渍土是CH4的汇,并受到土壤含水率和含盐量显著影响,在盐渍土开发利用中应考虑通过合理的水盐调控以提高土壤CH4汇的能力。     

Effects of salinity,drought, and priming treatments on seed germination and growth parameters of Lathyrus sativus L.

Germination of plants is one of the most important stages during their growth, which is often influenced by environmental stresses, especially drought and salinity. This study was conducted to investigate the effects of salinity and drought on seed germination and growth of Lathyrus sativus. The experiment was laid out in a completely randomized design with factorial arrangement in four replications. Salinity treatments were 0, 2, and 4 dS/m and drought treatments included 0, 0.4, 0.8, and 1.2 MPa. Salinity and drought treatments were prepared by using sodium chloride and polyethylene glycol 6000, respectively. The results showed that salinity and drought stresses decreased germination percentage, and root and radicle length.     

Application of biochar in mitigation of negative effects of salinity stress in wheat (Triticum aestivum L.)

Salinity is a major abiotic stress that affects crop production throughout the world. Biochar is an activated carbon soil conditioner that can alleviate the negative impacts of salinity. The research was conducted to evaluate the ameliorative effect of 1% and 2% of biochar application on wheat seed germination and growth attributes under salinity. Both levels of biochar improved the germination and growth conditions under salinity; however, 2% biochar level was more effective compared to 1% level. Root and shoot length increased up to 23% and11% with 2% biochar, respectively. The maximum increase of 16% and 10% in leaf water potential and osmotic potential was noted with 2% biochar at 150 mM salt. The decrease in proline content and soluble sugar at 2% biochar was 51% and 27%, respectively. Decrease in superoxide dismutase activity was 15.3% at 2% level of biochar under stress biochar mitigates the negative effects of salinity and improved wheat productivity.     

烤烟缓释肥料对烟株根系和光合特性的影响

试验研究了烟草缓释肥料对烟株根系活力、叶片光合特性、烟株干物质积累以及产量和产值的影响.结果表明,施用烟草缓释肥料可显著提高烟株根系活力、叶片叶绿素含量和净光合速率以及烟株干物质的积累,降低胞间CO2浓度,其中以每株施用45.45 g 烟草缓释肥料的效果最好,其次为每株施用38.63 g烟草缓释肥料.施用烟草缓释肥料能提高烟叶的产量和产值,减少烟草缓释肥料用量的处理虽然降低了烟叶产量,但因改善烟叶品质而提高其产值,缓释肥料对烟叶产值的影响以每株施用38.63 g烟草缓释肥料处理效果最好.     

The response of drought-tolerant sugar beet to salinity stress under field and controlled environmental conditions

Abstract

Thirty-four sugar beet drought-tolerant half-sib families were screened in greenhouse experiment under saline (16?dSm^?1) and normal conditions, and a subset of 10 tolerant genotypes were selected for evaluating of yield-related traits, Na⁺, K⁺, and α-amino-N nitrogen contents under saline field condition (12?dSm^?1). Drought-tolerant genotypes showed a different tolerance level under salt stress. Significant correlation was observed between EP2_s and STIEP2 in greenhouse with root yield (RY) in saline field condition. It should be possible that a simple measurement at 16?dSm^?1 in the greenhouse can be used as main part of sugar beet salt-tolerant breeding program. In total, genotypes SBSI-DR I-HSF14-P.23 (# 16) and 436B-HSF9-P.27 (# 26) were recognized as salt- and drought-tolerant genotypes with low Na⁺ and K⁺ contents in root and high white sugar content (WSC) and RY in field. A larger panel of genotypes to validate this kind of association is necessary.     

Ameliorative effect of selenium on tomato plants grown under salinity stress

The ability of selenium (Se) to counteract salt inhibitory effects in crop plants, especially in tomato, is still poorly documented. In order to examine the impact of Se addition on the growth, some biochemical parameters related to osmotic adjustment and antioxidant defense of salt-stressed tomato, a two-factorial experiment was conducted in a greenhouse. The plants were supplied with NaCl (0, 25, or 50 mM) and Se (0, 5, or 10 μM), individually or simultaneously. The results showed that salinity had a deleterious impact on plant biomass and physiological parameters studied. The application of Se alleviated this adverse effect by improving the integrity of cell membranes and by increasing leaf relative water content under stress conditions. Moreover, the application of 10 μM Se significantly increased the photosynthetic pigments concentration under salt stress. Salt stress also caused an inhibition of catalase activity, but its activity was restored in the presence of Se. The free radical scavenging activity significantly increased in plants subjected to 25 mM NaCl and supplied with 5 µM Se, compared to NaCl-alone treatment. Both physiological and biochemical results indicate that 10 µM Se treatment can increase plant performance under salt stress, especially under high NaCl concentration.

Abbreviations: CAT: catalase; Chl: chlorophyll; DPPH: 2,2-diphenyl-1-picrylhydrazyl; DW: dry weight; FW: fresh weight; POD: peroxidase; REL: relative electrolyte leakage; RWC: relative water content; free radical scavenging activity (FRSA); TW: turgid weight     

Effect of dimethylarsenic acid (DMAA) on growth,tissue arsenic,and photosynthesis of rice plants

The effect of dimethylarsenic acid (DMAA) applied to the root on arsenic (As) uptake and concentration, net photosynthesis (Pn), and growth parameters of rice (Oryza sativa L. cv. ‘Mercury') plants was studied. The experiment consisted of four treatments (0, 0.2, 0.8, and 1.6 mg As/L) with four replications in a completely randomized design. The DMAA was applied in nutrient solution as its sodium salt. The solution culture was changed every four days to avoid changes in the As chemical form. Arsenic uptake and concentration in shoot and root increased upon increased DMAA concentration in solution. Upon uptake, DMAA was readily translocated to the shoot. At the two higher rates of DMAA application (0.8 and 1.6 mg As/L), Pn and photosynthetic capacity were significantly decreased in response to tissue As concentration. Leaf area and dry matter production were also significantly reduced at the two higher rates of DMAA. At the lower rate (0.2 mg As/L) of DMAA application, there was no significant reduction in Pn or growth. Dimethylarsenic acid application did not affect nutrient allocation within the rice plant at concentration levels used in this study.     

Growth response and ion homeostasis in two bermudagrass (Cynodon dactylon) cultivars differing in salinity tolerance under salinity stress

Bermudagrass (Cynodon dactylon) is a salinity-tolerant turfgrass that has good use potential in the saline-alkali lands of warm regions. However, the systematic Na⁺ and K⁺ regulation mechanisms under salinity stress remain unclear at the whole plant level. Two bermudagrass cultivars differing in salinity tolerance were exposed to 0, 50, 100, 200, or 300 mM NaCl in a hydroponic system. Growth, absorption, transportation, and secretion of Na⁺ and K⁺, and gas exchange parameters were determined in both cultivars. K⁺ contents were decreased and Na⁺ contents and Na⁺/K⁺ ratios were increased in both bermudagrasses with increased salinity; however, lower Na⁺ content and Na⁺/K⁺ ratio and more stable K⁺ content were found in the leaves of the salinity-tolerant ‘Yangjiang’ than the salinity-sensitive ‘Nanjing’. Higher Na⁺ contents in root cortical cells were found than in the stele cells of ‘Yangjiang’, but the opposite was observed in ‘Nanjing’. Lower Na⁺ contents and higher K⁺ contents were found in vessels for ‘Yangjiang’ than for ‘Nanjing’. Salinity stress increased the selective transport of K⁺ over Na⁺ from roots to leaves and the Na⁺-selective secretion via salt glands, which were stronger in ‘Yangjiang’ than ‘Nanjing’. Net photosynthetic rate and stomatal conductance decreased in the two bermudagrasses with increased salinity; however, they were more stable in ‘Yangjiang’. The results suggested that bermudagrass could reduce Na⁺ accumulation and maintain K⁺ stability in leaves under salinity stress by restricting Na⁺ into vessels in roots, selectively transporting K⁺ over Na⁺ from roots to leaves, selectively secreting Na⁺ via leaf salt glands, and maintaining suitable stomatal conductance.     

Effects of biofertilizers and cycocel on some physiological and biochemical traits of wheat (Triticum aestivum L.) under salinity stress

In order to study the effects of biofertilizers and cycocel on some physiological and biochemical characteristics of wheat (Triticum aestivum L.) under salinity condition, a factorial experiment was conducted based on randomized complete block design with three replications under greenhouse condition in 2015. Treatments were included salinity in four levels [no salt (control or S₀), salinity 30 (S₁), 60 (S₂) and 90 (S₃) mM NaCl equivalent of 2.76, 5.53 and 8.3 dS m^?1, respectively], four biofertilizers levels [no biofertilizer (F₀), seed inoculation by Azotobacter chrocoocum strain 5 (F₁), Pseudomonas putida strain 186 (F₂), both inoculation Azotobacter + Pseudomonas (F₃)] and three cycocel levels [without cycocel as control (C₀), application of 600 (C₁) and 1000 (C₂) mg L^?1]. Results showed that salinity severe stress (90 mM) decreased chlorophyll content, relative water content (RWC), total chlorophyll, photochemical efficiency of PSII and yield of wheat. Whereas, soluble sugars and proline content, electrical conductivity (EC), the activity of catalase (CAT), peroxidase (POD), polyphenol oxidase (PPO) enzymes were increased. Similar results were observed in CAT, POD and PPO activities due to inoculation by biofertilizers and cycocel. Salinity at 30 mM increased the photochemical efficiency of PSII and chlorophyll content in plants grown under biofertilizer and cycocel treatment but with increasing salinity up to 90 mM mentioned parameters were decreased. The highest proline and soluble carbohydrate at all salinity levels were observed in plants treated in the highest cycocel level and Azotobacter+ Pseudomonas application. Generally, it was concluded that biofertilizers and cycocel can be used as a proper tool for increasing wheat yield under salinity condition.     

Genetic variability for responses to short‐ and long‐term salt stress in vegetative sunflower plants

Sunflower (Helianthus annuus L.) has been rated as moderately salt‐resistant, and variability for salt resistance has been detected within this crop. However, variability in salt‐resistance mechanisms has not been assessed. Osmotic tolerance, the relation of salt resistance with whole‐plant Na⁺ and K⁺ distribution and tissue Na⁺ tolerance were investigated in several sunflower inbred lines. Plants were grown under controlled conditions, in pots with sand and perlite irrigated with salinized (NaCl, –0.65 MPa) nutrient solution. Osmotic tolerance was assessed from the initial effects of the salt treatment on plant elongation in eleven sunflower lines. Long‐term salinity responses were evaluated in four of those lines, by assessing whole‐plant growth. A principal components analysis (PCA) was run on relative‐to‐control growth data, and this information was used to establish a relative resistance ranking, which indicated lines HAR2 > HAR1 > HA64 > HAR5. Osmotic tolerance was observed in HA64 and HAR2. The lines showed different degrees of Na⁺ accumulation, it was very low in some of them, but relative salt resistance was not associated to this trait. Tissue Na⁺ tolerance was deduced by comparing the percentage of dead leaves as a function of leaf blade Na⁺ accumulation, and it was higher in HAR1 than in the rest. These results indicate that variability for salt‐resistance mechanisms exists in sunflower. Osmotic tolerance and tissue Na⁺ tolerance were detected in different lines, highlighting that such variability may be exploited for increasing salt resistance in this crop.     

Effect of salinity on growth,mineral composition,and water relations of grafted tomato plants

A greenhouse experiment was designed in order to evaluate growth, water relations, and nutrient concentrations of grafted and ungrafted tomato plants grown under varying levels of salinity (0, 30, or 60 mM NaCl). Two cultivars, ‘Fanny’ and ‘Goldmar’, were grafted onto AR‐9704, using the cleft‐grafting method. Growth of grafted ‘Fanny’ plants was higher than that of ungrafted plants. Growth of ‘Goldmar’ plants was not affected by salinity treatments or grafting, but it was slower than for ‘Fanny’. Leaf turgor showed no significant differences between grafted and ungrafted plants or between salinity levels. The stomatal conductance (G_s) was higher for grafted than for ungrafted plants, and salinity decreased it significantly and progressively in both grafted and ungrafted plants and in both varieties. The concentrations of Na⁺ and Cl^– were significantly higher in ungrafted than in grafted ‘Fanny’ plants. ‘Fanny’ was more tolerant when grafted, probably due to reduced accumulation of Na⁺ and/or Cl^– in the shoot.     

Alleviation of salinity stress in red cabbage plants by urea and sulfur applications

Environmental stresses, such as salinity, are becoming critical constraints to plant production especially in arid and semi-arid regions, one of the main targets of agricultural studies is to combat the environmental stresses on plants. An open field experiment was carried out to study the influence of sulfur (S) and urea on red cabbage plants under salt stress. The experiment was arranged as a split-plot design with three replications, the main plots included sulfur levels (0, 350, and 700 kg ha^?1), while subplots included urea levels (0, 1, 2, and 4 g L^?1). Results showed that urea spraying and sulfur soil additions resulted in improvement of growth and yield, and raised the level of potassium and nitrogen while lowering sodium content in plant leaves under salt stress conditions. Generally, larger and heavier heads were found with the application of 700 kg ha^?1 sulfur and 2 g L^?1 urea.     

Invertase activity limits grain yield of maize under salt stress

Salt stress reduces grain yield of maize (Zea mays L.) due to poor kernel setting but not due to decreased grain filling. In the present study, it was tested whether acid invertase activity is decreased in developing kernels of maize under salt stress, and if assimilate supply is limited. The relatively salt‐sensitive maize hybrid Pioneer 3906 was compared with the more salt‐resistant hybrid SR 12. Salt stress caused a significant decrease in grain yield which was due to a 50% decrease in kernel number. No source limitation was observed, as the sucrose concentrations in kernels were significantly increased under salt stress for both genotypes. In contrast, glucose and fructose concentrations in kernels were significantly decreased. Salt stress caused a significant inhibition of soluble acid invertase activity to 19% in hydroponics 5 d after pollination (5 DAP) and to 50% in the soil culture experiment (2 DAP). The decrease in enzyme activity was the same for both genotypes. In the soil experiment, the highest soluble acid invertase activity was found 2 DAP with a steep decline until 8 DAP in Pioneer 3906. It is concluded that a decrease in acid invertase activity is a key factor associated with limited kernel setting under salt stress but additional factors may be responsible for genotypic differences.