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To our knowledge, little attention has been paid to evaluating ZnO nanoparticles (ZNPs) roles in plants grown under salinity stress. In this study, seeds of lupine ( Lupinus termis ) plants were grown in plastic pots and exposed to 0 (control) and 150 (S) mM NaCl with or without priming with different concentrations of ZnO [20 mg L −1 (ZNPs1), 40 mg L −1 (ZNPs2), and 60 mg L −1 (ZNPs3)] for 20 days. Salinized plants showed a reduction in plant growth parameters (root length, shoot length, fresh weight, and dry weight) and in the contents of photosynthetic pigments (chlorophyll a and b, and carotenoids) and Zn, as well as in the activity of catalase (CAT) against control plants. On the other side, salinity stress boosted the contents of organic solutes (soluble sugar, soluble protein, total free amino acids, and proline), total phenols, malondialdehyde (MDA), ascorbic acid and Na, as well as the activities of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) in stressed plants over control plants. However, seed-priming with ZNPs mostly stimulated growth of stressed plants, which was accompanied by reinforcement in the levels of photosynthetic pigments, organic solutes, total phenols, ascorbic acid and Zn, as well as in the activities of SOD, CAT, POD, and APX enzymes over stressed plants alone. On the contrary, priming with ZNPs caused a decrement in the contents of MDA and Na in stressed plants relative to salinized plants alone. It is worthy to mention that, this improvement in salt tolerance of plants primed with ZNPs was more obvious in plants primed with ZNPs3 and grown both in unstressed and stressed regimes. Thus, our findings suggest that seed-priming with ZNPs, especially 60 mg L −1 ZnO is an effective strategy that can be used to enhance salt tolerance of lupine plants.

A pot study was performed to examine the effect of plant growth-promoting rhizobacteria (PGPR) including Azospirillum lipoferum or Azotobacter chroococcum on growth criteria (leaf area and seedlings fresh and dry weight), pigments [chlorophylls (Chl a and b) and carotenoids], osmolytes (soluble sugars, soluble proteins and proline), nutrient uptake, antioxidant enzyme activities, and oxidative stress in maize plants under normal and salt-affected soils. The results showed that salt stress induced a reduction in growth traits, pigments, soluble proteins, K+, and K+/Na+ ratio. On the other side, it increased soluble sugars, proline, Na+, malondialdehyde (MDA), and the activity of peroxidase (POD) and catalase (CAT). Meanwhile, salt stress did not significantly change the activity of ascorbate peroxidase (APX) in maize plants. The inoculation using Azospirillum lipoferum or Azotobacter chroococcum significantly enhanced growth parameters, pigments, K+, osmolytes, K+/Na+ ratio, and the activity of CAT, POD, and APX of the salt-affected maize plants as well as uninoculated control plants. In addition, the results showed that both types of bacteria have attributed to lower MDA and Na+ in maize plants. Interestingly, Azospirillum lipoferum has affected more compared to Azotobacter chroococcum in control and salt-stressed plants. We, therefore, have observed in this study that microbial inoculation significantly improved plant physiological activities and that adding bacteria such as Azospiroillum or Azotobacter to the soil could mitigate the negative effects of salt stress on maize plants.

A pot experiment was conducted to determine the effects of Glomus mosseae inoculation on growth and some biochemical activities in roots and shoots of pepper (Capsicum annuum L. cv. Zhongjiao 105) plants subjected to four levels of NaCl [0 (control), 25 (low), 50 (medium), and 100 (high) mM] for 30 days, after 30 days of establishment under non-saline conditions. In mycorrhizal (M) plants, root colonization varied from 48 to 16 %. M plants had higher root and shoot dry weight and leaf area compared with non-mycorrhizal (NM) plants. Under salinity stress, M plants accumulated higher amounts of leaf photosynthetic pigments as well as soluble sugar, soluble protein, and total free amino acids in roots and shoots than those of NM plants. In contrast, the accumulation of proline was less intense in M plants than NM plants. Salt stress induced oxidative stress by increasing malondialdehyde (MDA) content; however, the extent of oxidative damage in M plants was less compared with NM plants due to G. mosseae-enhanced activity of superoxide dismutase (SOD) and peroxidase (POD). We concluded that inoculation with G. mosseae improved growth performance and enhanced salt tolerance of pepper plants via improving photosynthetic pigments and the accumulation of organic solutes (except proline), reducing oxidative stress, and enhancing antioxidant activities of the SOD-POD system.

The present study evaluates the potential of Sar gassum muticum (Sar) and Jan ia rubens (Jan) seaweeds for enhancing growth and mitigating soil-salinity in chickpea ( Cicer arietinum L.). Under control conditions, Sar and Jan extracts improved chickpea growth which was attributed to their potential for increasing photosynthetic pigments, K + and amino acids, particularly proline, in comparison with water-sprayed control. Upon stress imposition, chickpea growth was reduced in NaCl concentration-dependent manner, and principal component analysis (PCA) revealed Na + accumulation and oxidative damage as major determinants of sensitivity at high salinity. Furthermore, amino acid quantification indicated activation/deactivation of overall metabolism in roots/shoots, as an adaptive strategy, for maintaining plant growth under salt stress. Sar and Jan extract supplementations provided stress amelioration, and PCA confirmed that improved growth parameters at high salinity were associated with enhanced activities of superoxide dismutase and peroxidase. Besides, four key amino acids, including serine, threonine, proline and aspartic acids, were identified from roots which maximally contribute to Sar- and Jan-mediated stress amelioration. Sar showed higher effectiveness than Jan under both control and salt stress conditions. Our findings highlight “bio-stimulant” properties of two seaweeds and provide mechanistic insight into their salt-ameliorating action which is relevant for both basic and applied research.

A pot experiment was carried out to study the ameliorative role of foliar application of an extract of the halophyte Arthrocnemum macrostachyum (A. macrostachyum) on soybean (Glycin max L.) plants grown under salinity stress (0, 75, and 150 mM NaCl). Growth traits, content of photosynthetic pigments, osmolytes, ascorbic acid and total phenol, oxidative damage, and proteins pattern were determined. Growth parameters of soybean plants grown under both saline regimes (75 and 150 mM NaCl) were reduced except for the response to the foliar application of A. macrostachyum extract in either stressed or non-stressed plants. Foliar application of A. macrostachyum extract reinforced the photosynthetic pigment, soluble sugars, and soluble proteins content. Besides, it also minimized the negative impacts of salinity on soybean plants by decreasing the content of malondialdehyde (MDA) and hydrogen peroxide (H2O2). The results herein showed that the plant water extract and their interactions in the two NaCl levels increased the proline, total free amino acids, total phenols, and ascorbic acid content. Protein patterns in soybean leaves indicated protein expression suppression in soybean plants irrigated with 150 mM NaCl. The magnitude of suppression caused by the saline level was enhanced by using A. macrostachyum extract. The findings of this study indicate that the use of an extract of the halophyte A. macrostachyum can be considered as an unconventional and novel tool in the mitigation of salinity stress.

Cadmium (Cd) is a highly toxic heavy metal. Its emission is suspected to be further increased due to the dramatic application of ash to agricultural soils and newly reclaimed ones. Thereby, Cd stress encountered by plants will exacerbate. Acute and chronic exposure to Cd can upset plant growth and development and ultimately causes plant death. Microorganisms as agriculturally important biofertilizers have constantly been arising as eco-friendly practices owing to their ability to built-in durability and adaptability mechanisms of plants. However, applying microbes as a biofertilizer agent necessitates the elucidation of the different mechanisms of microbe protection and stabilization of plants against toxic elements in the soil. A greenhouse experiment was performed using and plant growth-promoting (PGP) bacteria ( and ) individually and integrally to differentiate their potentiality in underpinning various resilience mechanisms versus various Cd levels (0, 50, 100, and 150 mg/kg of soil). Microorganisms were analyzed for Cd tolerance and biosorption capacity, indoleacetic acid production, and phosphate and potassium solubilization . Plant growth parameters, water relations, physiological and biochemical analysis, stress markers and membrane damage traits, and nutritional composition were estimated. Unequivocal inversion from a state of downregulation to upregulation was distinct under microbial inoculations. Inoculating soil with and PGPB markedly enhanced the plant parameters under Cd stress (150 mg/kg) compared with control plants by 4.9% and 13.9%, 5.6% and 11.1%, 55.6% and 5.7%, and 9.1% and 4.6% for plant fresh weight, dry weight, net assimilation rate, and transpiration rate, respectively; by 2.3% and 34.9%, 26.3% and 69.0%, 26.3% and 232.4%, 135.3% and 446.2%, 500% and 95.6%, and 60% and 300% for some metabolites such as starch, amino acids, phenolics, flavonoids, anthocyanin, and proline, respectively; by 134.0% and 604.6% for antioxidants including reduced glutathione; and by 64.8% and 91.2%, 21.9% and 72.7%, and 76.7% and 166.7% for enzymes activity including ascorbate peroxidase, glutathione peroxidase, and phenylalanine ammonia-lyase, respectively. Whereas a hampering effect mediated by PGP bacterial inoculation was registered on levels of superoxide anion, hydroxyl radical, electrolyte leakage, and polyphenol oxidase activity, with a decrease of 0.53%, 14.12%, 2.70%, and 5.70%, respectively, under a highest Cd level (150 mg/kg) compared with control plants. The available soil and plant Cd concentrations were decreased by 11.5% and 47.5%, and 3.8% and 45.0% with and PGP bacterial inoculation, respectively, compared with non-inoculated Cd-stressed plants. Whereas, non-significant alternation in antioxidant capacity of sunflower mediated by action even with elevated soil Cd concentrations indicates stable oxidative status. The uptake of nutrients, ., K, Ca, Mg, Fe, nitrate, and phosphorus, was interestingly increased (34.0, 4.4, 3.3, 9.2, 30.0, and 1.0 mg/g dry weight, respectively) owing to the synergic inoculation in the presence of 150 mg of Cd/kg. However, strategies of microbe-induced resilience are largely exclusive and divergent. Biofertilizing potential of showed that, owing to its Cd biosorption capability, a resilience strategy was induced reducing Cd bioavailability to be in the range that turned its effect from toxicity to essentiality posing well-known low-dose stimulation phenomena (hormetic effect), whereas using and , owing to their PGP traits, manifested a resilience strategy by neutralizing the potential side effects of Cd toxicity. The synergistic use of fungi and bacteria proved the highest efficiency in imparting sunflower adaptability under Cd stress.

Background To our knowledge, the role of exogenous fluoride (F – ) on aluminum (Al)-stress mitigation in plants has not been investigated yet. In this experiment, barley ( Hordeum vulgaris ) seedlings were exposed to excessive Al 3+ concentrations (aluminum chloride, 0.5, 1.0, 2.0, 3.0, and 4.0 mM) with and without fluoride (0.025% sodium fluoride) to explore the possible roles of fluoride on the alleviation of Al-toxicity. Results Overall, Al-stress caused inhibition of growth and the production of photosynthetic pigments. Principal component analysis showed that the growth inhibitory effects were driven by increased oxidative stress and the interruption of water balance in barley under Al-stress. Fluoride priming, on the other hand, enhanced growth traits, chlorophyll a and b content, as well as invigorated the protection against oxidative damage by enhancing overall antioxidant capacity. Fluoride also improved osmotic balance by protecting the plasma membrane. Fluoride reduced endogenous Al 3+ content, restored Al-induced inhibition of glutathione-S-transferase, and increased  the contents of phytochelatins and metallothioneins, suggesting that fluoride reduced Al 3+ uptake and improved chelation of Al 3+ . Conclusions Aluminum chloride-induced harmful effects are abridged by sodium fluoride on barely via enhancing antioxidative responses, the chelation mechanism causing reduction of Al uptake and accumulation of barely tissues. Advanced investigations are necessary to uncover the putative mechanisms underpinning fluoride-induced Al-stress tolerance in barley and other economically significant crops, where our results might serve as a solid reference.

The release of harmful wastes via different industrial activities is the main cause of heavy metal toxicity. The present study was conducted to assess the effects of heavy metal stress on the plant growth traits, antioxidant enzyme activities, chlorophyll content and proline content of Sesbania sesban with/without the inoculation of heavy-metal-tolerant Bacillus gibsonii and B. xiamenensis. Both PGP strains showed prominent ACC-deaminase, indole acetic acid, exopolysaccharides production and tolerance at different heavy metal concentrations (50–1000 mg/L). Further, in a pot experiment, S. sesban seeds were grown in contaminated and noncontaminated soils. After harvesting, plants were used for the further analysis of growth parameters. The experiment comprised of six different treatments. The effects of heavy metal stress and bacterial inoculation on the plant root length; shoot length; fresh and dry weight; photosynthetic pigments; proline content; antioxidant activity; and absorption of metals were observed at the end of the experiment. The results revealed that industrially contaminated soils distinctly reduced the growth of plants. However, both PGPR strains enhanced the root length up to 105% and 80%. The shoot length was increased by 133% and 75%, and the fresh weight was increased by 121% and 129%. The proline content and antioxidant enzymes posed dual effects on the plants growing in industrially contaminated soil, allowing them to cope with the metal stress, which enhanced the plant growth. The proline content was increased up to 190% and 179% by the inoculation of bacterial strains. Antioxidant enzymes, such as SOD, increased to about 216% and 245%, while POD increased up to 48% and 49%, respectively. The results clearly show that the utilized PGPR strains might be strong candidates to assist S. sesban growth under heavy metal stress conditions. We highly suggest these PGPR strains for further implementation in field experiments.

In this study, the positive role of hydrogen peroxide (H2O2) pretreatment in mitigating the adverse impacts of seawater stress has been evaluated in two wheat (Triticum aestivum L.) cultivars, namely Gemmiza 11 as a salt-sensitive and Misr 1 as a salt-tolerant cultivar, with contrasting phenotypes in response to the salinity stress. Under normal conditions, wheat seeds eustress with H2O2 have shown significant effects on the improvement of plant growth parameters, such as dry weight and root and shoot lengths. Under salt stress conditions, seeds eustress with H2O2 have shown a reduction in damage to plant growth and physiological parameters as compared to the seeds kept as un-primed in both wheat cultivars. In addition, eustress of seeds with H2O2 has induced an increment in the pigments content, proline level and mineral uptake (K+, Ca2+ and Mg2+). Moreover, seeds eustress with H2O2 have shown significant decrement in Na+ content uptake in plants and that subsequently reduced lipid peroxidation. Seawater stress has increased the activity of the antioxidant system based on catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) in both cultivars, except POD in Gemmiza 11. Similarly, the application of H2O2 has further enhanced the activity of the antioxidant system in stressed plants and this enhancement of the antioxidant system further reduced Na+ content in plants and subsequently increased the growth parameters. Results of inter-simple sequence repeat (ISSR) markers have shown clear differentiation among the treatments and have provided strong evidence in support of the hypothesis proposed in this study that H2O2 eustress improves seed tolerance and enhances plant growth parameters under seawater stress.

A pot experiment was designed and performed in a completely randomized block design (CRBD) to determine the main effect of two plant growth-promoting rhizobacteria (PGPR) and their co-inoculation on growth criteria and physio-biochemical attributes of canola plants (Brassica napus L.) plant grown in saline soil. The results showed that inoculation with two PGPR (Azotobacter chroococcum and/or Alcaligenes faecalis) energized the growth parameters and photosynthetic pigments of stressed plants. Moreover, soluble sugars’ and proteins’ contents were boosted due to the treatments mentioned above. Proline, malondialdehyde (MDA), and hydrogen peroxide (H2O2) contents were markedly declined. At the same time, antioxidant enzymes, viz. superoxide dismutase (SOD), ascorbate peroxidase (APX), and peroxidase (POD), were augmented due to the inoculation with Azotobacter chroococcum and/or Alcaligenes faecalis. Regarding minerals’ uptake, there was a decline in sodium (Na) and an increase in nitrogen (N), potassium (K), calcium (Ca), and magnesium (Mg) uptake due to the application of either individual or co-inoculation with the mentioned bacterial isolates. This study showed that co-inoculation with Azotobacter chroococcum and Alcaligenes faecalis was the most effective treatment and could be considered a premium tool used in facing environmental problems, especially saline soils.