Mitigate Salt Stress Research Articles

Nitric oxide mitigates salt stress effects of pepper seedlings by altering nutrient uptake, enzyme activity and osmolyte accumulation.

This study was planned to evaluate the role of exogenous application of sodium nitroprusside (SNP), a NO donor, on the deleterious effect of salinity in Capsicum annum L. seedlings. Different NO doses (0, 50, 100 and 150µM SNP) were foliarly applied to pepper seedlings grown under the non-saline and saline conditions (50, 100 and 150mM of NaCl). The photosynthetic rate (Pn), stomatal conductance (gs), intercellular CO2 concentration (Ci), transpiration rate (Tr), mineral element (Zn, Fe, B, K, Ca and Mg) uptake, plant growth and leaf relative water content (LRWC) weredecreased by NaCl treatment, but NO treatments generally improved the observed parameters. 150mM NaCl treatment caused overaccumulation of hydrogen peroxide (H2O2) and malondialdehyde (MDA) by 87 and 100% respectively as compared to control. However, NO application (150µM SNP) at 150mM of NaCl significantly decreased H2O2 and MDA to 34 and 54%, respectively. The present study clarified that the exogenous NO treatment supported pepper seedlings against salinity stress by regulating the mineral nutrient uptake, antioxidant enzyme activity, osmolyte accumulation, and improving the LRWC and photosynthetic activity.

Polyphenol-enriched spelt husk extracts improve growth and stress-related biochemical parameters under moderate salt stress in maize plants

Biostimulants improve yield, quality, and stress acclimation in crops. In this work, we tested the possibility of using phenolics-rich extracts from spelt (Triticum dicoccum L.) husks to attenuate the effects of salt stress (100–200 mM NaCl) in maize. Two methanolic extracts were prepared from the soluble-conjugated (SC), and the insoluble-bound (IB) phenolic acid fractions of the spelt husk, and their effects were investigated on several stress-associated biochemical parameters, such as proline, lipid peroxidation, H2O2, GSH levels, and ion content. Results show that SC and IB fractions of husk extracts behaved very differently, no doubt due to their greatly divergent chemical composition, as revealed by both GC-MS and HPLC analyses. The efficacy of treatments in mitigating salt stress was also dose- and timing-dependent. IB, even at the lower concentration tested, was able to recover the performance of stressed plants in terms of growth, photosynthetic pigments content, and levels of salt stress markers. Recovery of shoot growth to control levels and reduction of stress-induced proline accumulation occurred regardless of whether plants were pre-treated or post-treated with IB, whereas only pre-treatment with the higher dose of IB was effective in mitigating oxidative stress. Although in some cases SC and even methanol alone exerted some positive effects, they could also be deleterious whereas IB never was. Overall, results indicate that a polyphenol-containing extract obtained from spelt by-products can behave as biostimulant in maize plants and can mitigate their response to salt stress, by acting on different biochemical targets.

Salt stress mitigation by calcium nitrate in tomato plant

Salt stress is one of the most subversive abiotic stress which severely affects the agricultural productivity in various ways. The pot experiment was conducted at the Horticulture Farm of Sher-e-Bangla Agricultural University, Dhaka during the period from November 2017 to April 2018. BARI Tomato-5 was used as planting material. The two factors experiment was laid out in RCBD with four replications. Five levels of salinity induced by sodium (Na+) viz., 0, 2, 4, 6 and 8 dS m-1 and three levels of Ca2+ viz., 0, 5 and 10 mM were used as treatment variables. The results of this experiment showed that, the salt stress reduced the yield parameters and yield of tomato with the increase of salinity. The lowest data was recorded from 8 dS m-1 and highest value was observed at control. The present results also showed that, Ca2+ significantly increased the yield contributing characters as well as yield of tomato in both saline and non-saline conditions. However, for combined effect, highest number of fruits plant-1 (50.8) and the highest yield plant-1 (3.88 kg) was produced from 0 dS m-1 Na x 10 mM Ca2+; whereas the lowest from 8 dS m-1 x 0 mM Ca2+. This result suggests that, exogenous Ca2+ can effectively mitigate the deleterious effect of salt stress in tomato.
 Asian J. Med. Biol. Res. March 2019, 5(1): 87-93

Physiological mechanisms of exogenous calcium on alleviating salinity-induced stress in rice (Oryza sativa L.).

Being more sensitive to salt stress among the cereals, growth of rice (Oryza sativa L.) has been habitually affected by salinity. Although, several practices have evolved to sustain the growth of rice under salinity, the enormous role of calcium (Ca2+) as a signalling moleculein salt stress mitigation is still arcane. Considering this fact, an experiment was performed aiming to explicate the mechanism of salt-induced growth inhibition in rice and its alleviation by exogenous Ca2+. At germination stage, 10mM and 15mM CaCl2 primed rice (cv. Binadhan-10 & Binadhan-7) seeds were grown in petri dishes for 9days under 100mM NaCl stress. At seedling stage, 9-day-old rice seedlings grown on sandwere exposed to 100mM NaCl alone and combined with 10mM and 15mM CaCl2 for 15days. This research revealed that salinity radically slowed down growth of rice seedlings and Ca2+ treatment noticeably improved growth performances. At germination stage, 10mM CaCl2 treatment significantly increased the final germination percentage, germination rate index (in Binadhan-7), shoot, root length (89.20, 67.58% in Bindhan-10 & 84.72, 31.15% in Bindhan-7) and biomass production under salinity. Similarly, at seedling stage, 10mM CaCl2 supplementation in salt-stressed plants enhanced shoot length (42.17, 28.76%) and shoot dry weight (339.52, 396.20%) significantly in Binadhan-10 & Binadhan-7, respectively, but enhanced root dry weight (36.76%) only in Binadhan-10. In addition, 10mM CaCl2 supplementation on salt-stressed seedlings increased the chlorophyll and proline content, and oppressed the accretion of reactive oxygen species thus protecting from oxidative damage more pronouncedly in Binadhan-10 than Binadhan-7 as reflected by the elevated levels of catalase and ascorbate peroxidase activity. The 15mM CaCl2 somehow also enhanced some growth parameters but overall wasless effective than 10mM CaCl2 to alleviate salt stress, and sometimes showed negative effect. Therefore, supplementary application of calcium-rich fertilizers in saline prone soils can be an effective approach to acclimatize salt stress and cultivate rice successfully.

In silico characterization of SAMdC from Pokkali rice and its overexpression in transgenic tobacco

Polyamines help to mitigate salt stress in plants. SAMdC or S-adenosyl methionine decarboxylase is a crucial enzyme in the polyamine biosynthetic pathway. Overexpressing the samdc gene of Pokkali (a salt-tolerant Indica rice landrace) in the model plant tobacco through Agrobacterium-mediated transformation resulted in tobacco plants capable of withstanding high salinity (200 mM) stress. The transgenic tobacco plants maintained a steady level of the higher polyamines and resisted ionic imbalance under salt stress. Since appropriate binding of the substrate with the enzyme is essential for an enzymatic reaction, we performed molecular docking experiment of SAMdC enzyme of Pokkali rice and tobacco to get an idea about its commonality in the two plants in the backdrop of Japonica rice and Arabidopsis. In silico characterization of SAMdC revealed that the enzyme used the same substrate in Pokkali rice and tobacco, from where the gene is introgressed and where it is overexpressed.

Boosting the Brassica napus L. tolerance to salinity by the halotolerant strain Pseudomonas stutzeri ISE12

Soil salinisation is one of the major pervasive environmental hazards and abiotic stress factors limiting plant productivity worldwide. Since most of the known crops are susceptible to high salinity, there is great interest in improving technologies in agriculture and making major crop species more robust and productive under saline conditions. In our work, we hypothesized that halotolerant plant growth promoting endophytic bacteria may have a beneficial effect on the growth and development of Brassica napus L. cultivated under salt stress conditions. The main aim of our study was to evaluate the role of the Pseudomonas stutzeri ISE12 strain, isolated from the halophyte Salicornia europaea, in mitigating salt stress in Brassica napus L. Verification of the influence of P. stutzeri on B. napus was based on the wide range of plant parameters responsible for abiotic and biotic stress factors: growth and biochemical parameters, the level of RSH gene expression, and changes in the chemical composition and physical properties of cell walls.In accordance with our assumption, salinity decreased plant growth and increased levels of proline, total glutathione and lipid peroxidation in plants. Inoculation of plants with the halotolerant P. stutzeri ISE12 increased the plant growth in both types of substrate (non-saline and saline) and decreased the accumulation of non-enzymatic antioxidants. The RSH1 and RSH3 gene expression in B. napus organs depended on the level of salinity and bacterial inoculation, while we have not observed effect of these biotic and abiotic factors in the case of CRSH and RSH2 genes. Moreover, increased levels and changes in the distribution of homogalacturonans (HGs) with varying de-esterification patterns were observed in cell walls in response to saline stress.In conclusion, inoculation of B. napus with the halotolerant strain P. stutzeri ISE12 alleviates the salt stress experienced by host plants by activating their antioxidant defence system and triggering the rearrangement of cell walls, which, consequently, promotes plant growth.

Effect of Preharvest Application of Silicon and Saline Water on Postharvest Quality of Beet (Beta vulgaris L.)

Beet is one of the vegetables richest in nutrient (bioactive compounds, folic acid and potassium). However, there are few studies on postharvest quality from the crop under irrigation conditions with saline waters, and because of that, the objective of this study was to evaluate effect of saline waters and silicon application in the preharvest on physicochemical quality of the beet. Two experiments were conducted with the objective of evaluating two forms of silicon application: via foliar (experiment 1) and via soil (experiment 2) about its influence in mitigating salt stress. In both experiments was adopted a randomized design with blocks in a 5 x 5 factorial, referring to five levels of electrical conductivity of the irrigation water (ECw): (0.5, 1.3, 3.25, 5.2 and 6.0 dS m-1) five doses of silicon (0.00; 2.64; 9.08; 15.52 and 18.16 mL L-1), they were combined according to the experimental matrix Central composite of Box totaling 10 treatments, with four replicates and three plants per plot. After harvesting, 70 days after transplanting, the following characteristics were evaluated: bulb dry mass, pH, titratable acidity (TA), total soluble solids (TSS), TSS/TA ratio and ash. There was a significant effect for the salinity x silicon (Si) interaction applied via soil to the dry matter mass and titratable acidity. The electrical conductivities of irrigation water (ECw) and Si doses via leaf and soil influenced significantly for analyzed variables, except pH, total soluble solids, TSS/TA ratio, ash and titratable acidity, which were not influenced by ECw and nor by the doses of Si via soil and foliage. Irrigation with water of 6.0 dS m-1 promotes better quality beet tuber. The fertilization on preharvest with silicon via soil or foliage improved postharvest quality of beet.

Morfofisiologia de aceroleira irrigada com águas salinas sob combinações de doses de nitrogênio e potássio

This research aimed to evaluate the effect of different combinations of nitrogen and potassium doses on the growth and physiology of the crop of the West Indian cherry irrigated with saline waters. The experiment was carried out in the field at the CCTA/UFCG, in a randomized block design, with treatments arranged in a 5 x 4 factorial scheme, referring to five irrigation water salinities (ECw) of 0.3, 1.3, 2.3, 3.3 and 4.3 dS m-1 and four combinations (C) of doses of nitrogen (N) and potassium (K2O), with C1 = 70% N + 50% K2O; C2 = 100% N + 75% K2O; C3 = 130% N + 100% K2O and C4 = 160% N + 125% K2O, with three replications, one plant per plot, totaling 60 plots without border. Most of the growth and physiological variables were not compromised by irrigation with water salinity up to 4.3 dS m-1 and, there was no salt stress mitigation by combinations of doses of nitrogen and potassium fertilization. The combination of the doses of 70% N (35 g of N) + 50% K2O (20 g of K2O per plant) was more effective in increasing the gas exchange, promoting greater plant growth.

ITRAQ-Based Protein Profiling and Biochemical Analysis of Two Contrasting Rice Genotypes Revealed Their Differential Responses to Salt Stress.

Salt stress is one of the key abiotic stresses causing huge productivity losses in rice. In addition, the differential sensitivity to salinity of different rice genotypes during different growth stages is a major issue in mitigating salt stress in rice. Further, information on quantitative proteomics in rice addressing such an issue is scarce. In the present study, an isobaric tags for relative and absolute quantitation (iTRAQ)-based comparative protein quantification was carried out to investigate the salinity-responsive proteins and related biochemical features of two contrasting rice genotypes—Nipponbare (NPBA, japonica) and Liangyoupeijiu (LYP9, indica), at the maximum tillering stage. The rice genotypes were exposed to four levels of salinity: 0 (control; CK), 1.5 (low salt stress; LS), 4.5 (moderate salt stress; MS), and 7.5 g of NaCl/kg dry soil (high salt stress, HS). The iTRAQ protein profiling under different salinity conditions identified a total of 5340 proteins with 1% FDR in both rice genotypes. In LYP9, comparisons of LS, MS, and HS compared with CK revealed the up-regulation of 28, 368, and 491 proteins, respectively. On the other hand, in NPBA, 239 and 337 proteins were differentially upregulated in LS and MS compared with CK, respectively. Functional characterization by KEGG and COG, along with the GO enrichment results, suggests that the differentially expressed proteins are mainly involved in regulation of salt stress responses, oxidation-reduction responses, photosynthesis, and carbohydrate metabolism. Biochemical analysis of the rice genotypes revealed that the Na+ and Cl− uptake from soil to the leaves via the roots was increased with increasing salt stress levels in both rice genotypes. Further, increasing the salinity levels resulted in increased cell membrane injury in both rice cultivars, however more severely in NPBA. Moreover, the rice root activity was found to be higher in LYP9 roots compared with NPBA under salt stress conditions, suggesting the positive role of rice root activity in mitigating salinity. Overall, the results from the study add further insights into the differential proteome dynamics in two contrasting rice genotypes with respect to salt tolerance, and imply the candidature of LYP9 to be a greater salt tolerant genotype over NPBA.

Strategy of Ginkgo biloba L. in the mitigation of salt stress in the urban environment

Ginkgo biloba is recommended in street plantings in many countries due to its resistance to urban conditions. Our research confirmed the relatively low sensitivity of G. biloba to unfavorable urban conditions salt stress. The research consisted of two field experiments with urban trees and a controlled potted experiment with young trees. There was a large diversity of reactions between the older street trees and the young trees from the pot experiment. In both experiments, the leaves demonstrated high values of Cl and Na. The street tree leaves contained an average of 1.13% Cl and 1061 mg kg−1 Na. In the pot experiment, depending on the NaCl dose, the Cl content ranged from 0.07% to 4.80%, and Na ranged from 40.4 mg kg−1 to 7953 mg kg−1. The street tree leaves did not have any damage, and in the pot experiment, the first measurable damage to the leaves appeared with leaf Cl and Na contents of 2.42% Cl and 4.86 mg kg−1 Na. The health conditions of the leaves, even at the highest levels of Cl and Na, were not bad (damage index of 2.4 on a six-point scale). In urban conditions, an increasing amount of Cl was accompanied by an increase in polyprenols in the leaves. In the model experiment, there was no increase in the content of these compounds with a concomitant increase in the NaCl dose. The G. biloba strategy may rely on the ability to synthesize polyprenols acquired during the process of adaptation. This ability was only possessed by older street trees; young trees in the pot experiment did not develop this ability.

Mitigation of salt stress by dual application of arbuscular mycorrhizal fungi and salicylic acid

Mitigation of salt stress by dual application of arbuscular mycorrhizal fungi and salicylic acid

The Contribution of Nano-Selenium in Alleviation of Salinity Adverse Effects on Coriander Plants

Nanotechnology is the field of science that opens a large scope of novel application in various fields, especially agricultural biotechnology. Selenium (Se) is an essential trace element for humans and animals and appears to be a beneficial element for many plants. There is increasing evidence showing that low selenium (Se) concentrations may build resistance of plants to environmental stresses. For this purpose, a pot experiment was carried out at The Experimental Farm of the Faculty of Agriculture, Mansoura University, Dakahlia Governorate, Egypt, during the spring season of 2016, to investigate the potential alleviation of salinity adverse effects by Se application as a foliar spray in the form of selenium nanoparticles (Se-NPs) in two concentrations (0 and 50 ppm) on coriander (Coriandrum sativum) grown on a sandy soil irrigated with different concentrations of saline water S1 (ECw=3.12 dS m-1), S2 (ECw =6.25 dS m-1) and tap water as a control S0 (ECw=0.45 dSm-1). These experimental treatments were arranged in a split plot design in three replications. Salinity showed adverse effects on different plant growth parameters as well as total chlorophyll content. Selenium nanoparticles (Se-NP1) at 50 ppm showed the best effects on vegetative growth and total chlorophyll content of coriander plants under different salinity levels of irrigation water. Increasing salinity resulted in decreasing N and K contents in the leaves of coriander plants, but Na increased as a result of some sort of antagonism with K; in spite of that, N and K contents in coriander leaves increased with foliar application of selenium nanoparticles (Se-NP1) at rate of 50 ppm to be higher concentrations compared to distilled water added to the spray as a control 0 ppm (Se-NP0). Values of Na/K ratio in coriander leaves increased as the salinity levels increased while, K/Na ratio was decreased. On the contrary, the values of Na/K ratio decreased with (Se-NP1) spraying at rate of 50 ppm, but K/Na ratio was increased at the same spraying rate under all salinity levels. It is concluded that application of selenium nanoparticles can mitigate salt stress damages on coriander plants; it also leads to increasing in K concentrations and decreasing in Na concentrations under salt stress.

Growth and gas exchanges in soursop under irrigation with saline water and nitrogen sources

ABSTRACT Nitrogen (N) fertilization has been tested for the mitigation of salt stress in some species including fruit crops. However, special attention should be paid to the source of N, due to the different compositions and saline indices of the fertilizers, particularly when irrigation is conducted using waters with salinity levels that are restrictive to agriculture. Thus, this study evaluated the effect of fertilization with N sources on the growth and gas exchanges of soursop irrigated with saline water after transplanting. The experiment was carried out in greenhouse at the Center of Technology and Natural Resources of the Federal University of Campina Grande, and treatments were arranged in randomized blocks, in 4 x 4 factorial scheme, corresponding to electrical conductivity of water - 0.5, 1.1, 2.5 and 3.5 dS m-1, and the N sources urea, ammonia sulfate, calcium nitrate and potassium nitrate, with three replicates. Growth and gas exchanges of soursop at 110 days after transplanting were not influenced by either the interaction between water salinity and N sources or the individual action of N, but were inhibited by the increase in water salinity from 0.5 dS m-1. Increasing water salinity inhibited stomatal opening and carboxylation in the leaves.

Humic acid and boron treatment to mitigate salt stress on the melon plant

Salinity is one of the main abiotic stress factors which limit the growth and productivity of plants, however, the nutritional status of plants is the first brick in the resistance wall against stresses. Therefore, a factorial experiment was undertaken to investigate effects of soil applied humic acid (0, 7, 14, 21 l.ha-1) and boron foliar spraying (0, 50, 100 ppm) and their interaction on growth and yield of melon plant under saline conditions. The results suggested that the treatments soil application of humic acid and the boron spraying successfully mitigated the deleterious effects of salt stress and influenced growth and yield of melon plant. Humic acid at 21 l.ha-1 or boron spray at 50 ppm exhibited an improvement in growth and yield of melon, in terms of plant length, plant fresh and dry mass, chlorophyll (SPAD), fruit mass, total yield, and also leaf nutrient content (N and K) and total soluble solids (TSS) of fruits, while reduced the sodium content of leaves. The combined treatment of humic acid at 21 l.ha-1 and boron spraying at 50 ppm was found to be more effective for the melon plant to improving growth performance and the crop yield by 21 % as compared with the control group under saline conditions.

Paclobutrazol mitigates salt stress in indica rice seedlings by enhancing glutathione metabolism and glyoxalase system

Stress-induced methylglyoxal (MG) functions as a toxic molecule, inhibiting plant physiological processes such as photosynthesis and antioxidant defense systems. In the present study, an attempt was made to investigate the MG detoxification through glutathione metabolism in indica rice [Oryza sativa L. ssp. indica cv. Pathumthani 1] under salt stress by exogenous foliar application of paclobutrazol (PBZ). Fourteen-day-old rice seedlings were pretreated with 15 mg L−1 PBZ foliar spray. After 7 days, rice seedlings were subsequently exposed to 0 (control) or 150 mM NaCl (salt stress) for 12 days. Prolonged salt stress enhanced the production of MG molecules and the oxidation of proteins, leading to decreased activity of glyoxalase enzymes, glyoxalase I (Gly I) and glyoxalase II (Gly II). Consequently, the decreased glyoxalase activities were also associated with a decline in reduced glutathione (GSH) content and glutathione reductase (GR) activity. PBZ pretreatment of rice seedlings under salt stress significantly lowered MG production and protein oxidation, and increased the activities of both Gly I and Gly II. PBZ also increased GSH content and GR activity along with the up-regulation of glyoxalase enzymes, under salt stress. In summary, salinity induced a high level of MG and the associated oxidative damage, while PBZ application reduced the MG toxicity by up-regulating glyoxalase and glutathione defense system in rice seedlings.

Effect of Vermicompost Supplemented by Foliar Application of Silicate on Marjoram Plants Grown in Saline Soil

This study aimed to reduce the negative effects of soil salinity on marjoram plants by adding vermicompost to the saline soil complemented by foliar application of silicate (Si +2 ) to their leaves. To achieve this purpose in field, the experiment was arranged as a factorial experiment. (Two way) Based on randomized complete block design with four replications. The first factor was vermicompost which was added at four rates (0, 3, 4 and 5 ton fed -1 ). The second factor was silicon which was used at four rates (0, 2.5, 3.75 and 5 mM). Results revealed that the single application of either vermicompost or silicon reduced Na and proline concentration in plant shoot and enhanced plant growth, nutrient content, carbohydrate percentage and essential oil yield in plant shoots. This increase remained constant and not correlated with the rates of application. The combined application of vermicompost and foliar spraying of silicon resulted in noticeable increase in plant growth, nutrient content (N, P, K and Ca), carbohydrate percentage and essential oil yield in marjoram plants; the highest values of all parameters were recorded by using vermicompost at rate 3 or 4-ton fed -1 coupled with spraying 3.75 mM of silicon solution on plant leaves. These results proved that amendment of saline soil by adding vermicompost and spraying silicon solution on plant leaves directly is a good strategy for the reclamation of saline soil and mitigation of salt stress within plant tissues.

Melatonin Mitigates Salt Stress in Wheat Seedlings by Modulating Polyamine Metabolism.

Melatonin, a small molecular weight indoleamine molecule, is involved in various biological processes and responses to environmental cues in plants. However, its function in abiotic stress response and the underlying mechanisms is less clear. In this study, we investigated the effect of melatonin on wheat seedlings growth under salt stress condition. Exogenous melatonin pretreatment partially mitigated the salt-induced inhibition of whole-plant growth as judged from shoot dry weight, IAA content, leaf photosynthesis rate, maximum photochemistry efficiency of photosystem II, and chlorophyll. The mitigation was also observed in reduced accumulation of H2O2 in melatonin-pretreated wheat seedlings exposed to salt stress. Exogenous melatonin increased endogenous melatonin content by evaluating the levels of TaSNAT transcript, which encodes a key regulatory enzyme in the melatonin biosynthetic pathway. Furthermore, melatonin increased polyamine contents by accelerating the metabolic flow from the precursor amino acids arginine and methionine to polyamines; melatonin also decreased the degradation of salt-induced polyamines. Taken together, these results provide the evidence that melatonin mitigates salt stress mainly through its regulation on polyamine metabolism of wheat seedlings.

Bacterial microbiome of root-associated endophytes of Salicornia europaea in correspondence to different levels of salinity

The halophytes have evolved several strategies to survive in saline environments; however, an additional support from their associated microbiota helps combat adverse conditions. Hence, our driving interests to investigate the endophytic bacterial community richness, diversity, and composition associated to roots of Salicornia europaea from two test sites with different origins of soil salinity. We assumed that salinity will have a negative effect on the diversity of endophytes but simultaneously will permit the high occurrence of halophylic bacteria. Further, to establish the role of the host and its external environment in determining the endophytic diversity, we analyzed the physico-chemical parameters of root zone soil and the concentration of salt ions in the plant roots. The results based on the Miseq Illumina sequencing approach revealed a higher number of endophytic bacterial OTUs at naturally saline test site with a higher level of soil salinity. Proteobacteria and Bacteriodetes were the dominant endophytic phyla at both analyzed sites; additionally, the high occurrence of Planctomycetes and Acidobacteria at more saline site and the occurrence of Firmicutes, Actinobacteria, and Chloroflexi at less saline site were recorded. The salinity in the root zone soil was crucial in structuring the endophytic community of S. europaea, and the significant prevalence of representatives from the phyla Deltaproteobacteria, Acidobacteria, Caldithrix, Fibrobacteres, and Verrucomicrobia at the more saline test site suggest domination of halophylic bacteria with potential role in mitigation of salt stress of halophytes.

Hydroponic lettuce yields are improved under salt stress by utilizing white plastic film and exogenous applications of proline

Abstract Greenhouse crops are often affected by salinity due to water quality decay associated with crop fertilization and irrigation managements as well as the fact that greenhouse environment may become even hotter during summer time. Thus, combined effects of salt, heat and light stresses can affect plants grown in greenhouse. This research work addressed the combined effect of white greenhouse covering film and foliar proline spray application to reduce the detrimental effects of salinity on two cultivars of lettuce (Lactuca sativa cv. Teide and cv. Impulsion) grown on a floating system. Five different experiments were conducted in two twin greenhouses covered with plastic films characterized by different light permeability. The experiments aimed at identifying the most suitable nutrient solution (exp. #1), and assessing how the effects of mild salinity (0–15 mM NaCl) would be alleviated by the greenhouse covering film (exp. #2, #3, #4 and #5) and foliar proline spray application (0–15 μM) (exp. #4 and #5). Results showed that the white covering film changed the spectral light intensity and decreased the Photosynthetically Active Radiation (PAR) of the light transmitted causing a delay in the plant growth and leaf chlorophyll content. Although salinity negatively affected plant growth and leaf photosynthesis of both cultivars, using the white film partially mitigated the influence of salt stress. The beneficial effects of the white film on salt stress mitigation were more evident during summer and in the heat sensitive genotype (cv. Teide) in terms of greater total and marketable yield as compared to control conditions. Exogenous application of foliar proline (up to 5 μM) increased the yield under control condition and enhanced the plant response to salinity. Overall, for summer cultivation of cv. Teide, in presence of saline water (15 mM NaCl), the combination of both white covering film and proline application enabled to preserve efficiently the plant growth and final yield.

Potassium nitrate priming mitigates salt stress on wheat seedlings

Seeds of wheat (Triticum aestivum L., cv. Jadeide 11) were used to investigate the effects of potassium nitrate priming on germination and early seedling growth under salt stress. It was hypothesized that priming with potassium nitrate may improve seed germination and plant establishment by mitigating the negative effects of saline stress through its role in cell osmotic balance. The seeds were soaked in distilled water or in a 10 g L–1 KNO3solution at 25 °C for 2 hours, and after drying, were distributed in plastic boxes with blotter paper containing different salt solutions prepared with concentrations of 0 (control), 25, 50, 75 and 100 mmol L–1 NaCl. The plastic boxes were kept in a seed germinator, at 22 °C for 12 days. A completely randomized design in a 2 × 5 factorial scheme with four replications of 50 seeds each was used. The primed seeds with KNO3 showed improved germination performance, early growth and vigor index of wheat seedlings in salt stress conditions. Low salt concentrations may induce osmotic adjustment activity in the wheat plants and lead to increases in shoot and root length of wheat seedlings, whereas higher concentrations cause severe inhibition of plant growth. The ‶Jadeide 11″ wheat cultivar is a moderately tolerant genotype to salt stress during the seedling establishment stage by presenting yield stability index greater than 0.74 until the level of 100 mmol L–1 of NaCl, and therefore can be recommended for cropping in soils with high salinity levels.