Soil Biology, Biochemistry and Biotechnology
Farzaneh Dehdari; Mehdi Mehrabi-Koushki; Hamid Alvanipour; Jamshid Hayati
Abstract
Introduction: Soil contamination by crude oil is common in oilfield in different processes including extraction, transfer and refining of crude oil and its products. Bioremediation is an interesting strategy to remediation of soils polluted with crude oils and its derivatives. This method is based on ...
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Introduction: Soil contamination by crude oil is common in oilfield in different processes including extraction, transfer and refining of crude oil and its products. Bioremediation is an interesting strategy to remediation of soils polluted with crude oils and its derivatives. This method is based on the employed of organisms to neutralize oils in the environment. During bioremediation process, microorganisms degrade and transform persistent crude oil hydrocarbons into simple and less persistent molecules. It is very important to identify the microorganisms that can utilize and degrade these pollutants. Generally, fungi play an essential role in the biodegrading and remediation of soils polluted with hydrocarbons. Therefore, the present study was carried out to evaluate the tolerance of the fungal isolates obtained from the oil-contaminated soil to crude oil in Maroon oilfield.Materials and Methods: Twenty-three fungal isolates belonging to 12 genera were used to investigate their toleration to crude oil. The fungi had been isolated in December 2016 from soil samples contaminated with crude oils from four sites in the maroon oilfield of Ahwaz. The fungal isolates were obtained from the fungal collection of the department of plant protection of shahid chamran university of Ahvaz. The fungi had been identified based on phylogenetic analysis and morphological characteristics. The tolerance of these fungi to crude oil was studied by growing them on PDA medium containing 30, 40, and 50% concentrations of crude oil and through Radial growth measurements. The tolerance to crude oil was calculated based on growth inhibition percentage of fungal isolates. The research was conducted in a factorial completely randomized design for analysis of the growth-inhibitory percentages.Three replications were performed for each control (PDA-Tween culture medium without crude oil) and treatment. Mean data comparisons were performed based on Duncan's multi-range method at 1% significance level (P<0.01), using SAS 9.1 software.Results and Discussion: All isolates grew in the culture medium containing different concentrations of crude oil. The results of variance analysis showed significant difference between the main effects of isolates and different levels of crude oil, as well as their interaction effects on growth inhibition (P< 0.01). The growth inhibition means of three concentrations of 50, 40, and 30% was 33.6, 26.1, and 21.4, respectively, which indicated the direct relationship between the concentration level and the growth inhibition percentage. Naturally crude oil is a heterogeneous mixture that composed of hydrocarbons compounds, sulfur and other heavy elements, therefore an increase in its concentration leads to an addition in its toxicity. Comparisons of the mean of growth inhibition in different isolates in response to crude oil concentrations demonstrated that Aspergillus sp. SCUA-Deh-3 with 65.1 inhibition growth and placed in the group a had the lowest growth ability and highest sensitivity to oil and statistically significant difference exists between this isolate and all fungi (P< 0.01). M. circinelloides SCUA-34 and Cladosporium puyae SCUA-m5f4 ranked next with 45.1 and 41.8 inhibition of growth respectively and were placed in group b. Alternaria destruens SCUA-Deh-1 and Aspergillus sp.SCUA with 5.05 and 6.5 inhibitions and placed in group M had the lowest sensitivity and inhibition and had significant difference with all other fungi (P> 0.01). Also, the growth rate of both used Alternaria isolates enhanced by increasing oil concentration in media. The growth inhibition means were equal only in two isolates, Penicillium chrysogenum SCUA-Deh-12 and Aspergillus sp. SCUA-m1f8r2, in two concentrations of 30 and 40 % (4.6 and 19.6, respectively). Also, Aspergillus sp. SCUA-m3f10 had equal means percent inhibition of growth in two concentrations of 40 and 50 (28.5). Furthermore, in the isolates of Aspergillus sp. SCUA-Deh-3 initially stimulated growth at 40% concentration and then the growth inhibition percentage increased at concentration of 50%.Conclusion: These results showed that Alternaria destruens SCUA-Deh-1 and Aspergillus sp. SCUA-m1f7r2 have more growth potential than other fungi at presence of crude oil in growth medium. Also, the growth inhibition of Alternaria decreased by increasing of crude oil concentration. In other words, these two isolates were considered the most tolerant isolates to crude oil. So it seems; these native isolates are among the best fungi for bioremediation of oil-contaminated soils. However, regarding the biological degradation of petroleum materials, it seems necessary to mention that physicochemical properties and bioavailability of hydrocarbon pollutants play an important roles in their bioremediation.
Soil Biology, Biochemistry and Biotechnology
Elham Sadeghi; REZA GHORBANINASRABADI; Seyed Ali Reza Movahedi Naini; Mojtaba Barani Motlagh; Mostafa Khoshhal Sarmast; Mohammad Reza Pahlevan Rad
Abstract
Introduction: Plant growth and crop productivity may be adversely affected under unfavorable environmental conditions, such as a lack of organic matter in the soil. To counteract the negative impacts of these challenges, a unique strategy is required. The paucity of organic inputs, which is common in ...
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Introduction: Plant growth and crop productivity may be adversely affected under unfavorable environmental conditions, such as a lack of organic matter in the soil. To counteract the negative impacts of these challenges, a unique strategy is required. The paucity of organic inputs, which is common in conventional agricultural production, can lead to soil degradation, erosion, and loss of soil organic matter, which are unfortunate consequences. Soil organic amendments have been shown to have beneficial effects on crop production and a wide range of soil properties in agricultural systems. However, the limited availability of phosphorus (P) in soil can significantly restrict crop growth and productivity, particularly in maize crops. Adequate P supply has been found to enhance early maturity, crop quality, and yield. However, the prolonged use of chemical fertilizers such as NPK has been found to have adverse effects on soil fertility and crop quality. As a result, the combined application of organic and chemical fertilizers has been proposed as an effective approach compared to the single application of organic or chemical fertilizer alone. Therefore, this study aimed to assess the potential benefits of using compost and Triple Super Phosphate fertilizer (TSP) application on the chemical and biological properties of soil, as well as the properties of forage maize (cv. SC704), in loess soil.Materials and Methods: A factorial experiment was conducted using a completely randomized design with three replications. A total of 36 samples were performed in two separate cultivated and incubated experiments. A pot experiment was conducted to invwstigate the effects of simple and enriched compost, containing urea and Streptomyces, and varying amounts of TSP fertilizer (0, 10, 40, and 100 mg/kg), on soil properties and maize plant growth. In addition, an incubation experiment was conducted to measure the effects of the same treatments on soil microbial biomass and activity. The effect of treatments were analyzed as factorial under a completely randomized design. The biomass of maize plants was measured at the time of harvesting (the time from planting to harvesting of forage maize was 80 days). Some parameters such as available phosphorus, substrate-induced respiration, microbial biomass carbon, and some enzyme activity (acid phosphatase, alkaline phosphatase, catalase and urease) were measured in soil.Results and Discussion: The findings of this study indicated that the application of compost and TSP fertilizer had significant effects on plant biomass. Specifically, compost application led to an increase in microbial biomass carbon and enzymes activity (acid phosphatase, alkaline phosphatase, catalase and urease) in the soil, ultimately promoting plant growth. Moreover, the combined application of compost and TSP fertilizer increased the availability of phosphorus, substrate-induced respiration, and microbial biomass carbon in the soil. Based on the findings, the combined application of TSP and compost resulted in further increases in substrate-induced respiration (63-168%), microbial biomass carbon (72-167%), available phosphorus (29-103%), and enzyme activity (acid phosphatase (4-21), alkaline phosphatase (14-34%), catalase (13-32%), and urease(54-159%)) compared to the application of each amendment alone. This suggests that the addition of both TSP and compost promotes the availability of easily accessible nutrients for microbial growth and soil enzymes (acid phosphatase, alkaline phosphatase, catalase and urease) activity. The highest amount of available phosphorus, microbial biomass carbon, substrate-induced respiration, catalase activity and urease activity in cultivated soil (23%, 270%, 93%, 68%, 1.8%, respectively) and incubated soil (18%, 243%, 90%, 53%, 1.2%, respectively) were observed in C2P3 treatment. The results also indicated that the enriched compost+TSP treatment led to the highest substrate-induced respiration and microbial biomass carbon, followed by simple compost+TSP, enriched compost only, simple compost only, TSP fertilizer only, and the control. The increase in enzyme activity (P<0.01, r=0.90), and available phosphorus (P<0.01, r=0.60) in the soil positively influenced plant growth. Specifically, the simultaneous application of compost and TSP had a greater effect on maize plant biomass. The highest root biomass (2.80 g), stem biomass (10.4 g), and leaf biomass (2.27 g) were observed in the enriched compost and 100 mg kg-1 TSP treatment, which differed significantly from the other treatments.Conclusion: The results of this study demonstrated that the addition of compost and TSP to loess soils can promote microbial biomass carbon, substrate-induced respiration, enzyme activity (acid phosphatase, alkaline phosphatase, catalase, and urease), available phosphorus, and maize plant growth. Moreover, the use of compost can protect soil microbial and enzymatic activities in loess soils. Thus, the simultaneous application of enriched compost with TSP can reduce the use of chemical fertilizers and their negative environmental impacts.
Soil Biology, Biochemistry and Biotechnology
Morvarid HemmatiTabar; Setareh َAmanifar; Elaheh Vatankhah; Elham Malekzadeh
Abstract
Introduction: Nickel (Ni) is a fundamental micronutrient in plants but hampers plant growth and metabolism at elevated levels in the soil. Ni toxicity to plants is manifested mainly by the decrease in germination efficiency, the inhibition of growth and root branching, damage to the photosynthetic apparatus, ...
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Introduction: Nickel (Ni) is a fundamental micronutrient in plants but hampers plant growth and metabolism at elevated levels in the soil. Ni toxicity to plants is manifested mainly by the decrease in germination efficiency, the inhibition of growth and root branching, damage to the photosynthetic apparatus, and the induction of oxidative stress. In recent years, the use of arbuscular mycorrhiza (AM) has gained importance for its role in enabling plants to tolerate Ni toxicity. However, information about their effectiveness in alleviating Ni stress is scanty. The process of element transport in plants may be assumed to be different among heavy metal concentrations in the substrate. Consequently, whether AM fungi enhance the metal transport to shoots (phytoextraction) or immobilize them in the roots (phytostabilization) mainly depends on metal concentration in the substrate. Moreover, Ni has been reported to compete with other micronutrients for absorption sites, which would trigger different changes of elements concentrations. The aim of this study was to investigate the role of AM fungus in alleviating Ni stress and its possible function in plant nutrition.Materials and Methods: In this study, the effects of mycorrhizal inoculation of corn plants with Claroideoglomus etunicatum on alleviation of Ni impact on plant were evaluated. Some growth characteristics of the plant, phosphorus content, micronutrients (iron, zinc, and copper), concentration of nickel in shoot and root, and Bradford reactive soil glomalin (BRSG) were assessed. Accordingly, a two-factor experiment (AM inoculation × Ni levels) in completely randomized design was done. The factors included the different concentrations of nickel (control (Ni0), 50 (Ni50), 100 (Ni100) and 250 (Ni250) mg kg-1), and the levels of fungal application (control without inoculation (NM) and inoculated with C. etunicatum (AM)). Plants were grown in the greenhouse for 90 days and then the growth parameters were recorded. The concentration of phosphorus was measured spectrophotometrically and the concentration of iron, zinc, copper, and nickel in digested plant samples was determined by ICP-OES. Bio-concentration factor and translocation factor were also calculated. The colorimetric method was used to quantify Bradford-reactive soil glomalin. The Bradford protein assay was utilized to determine the concentration of easily extractable and total Bradford-reactive soil glomalin using bovine serum albumin (BSA) as a standard.Results and Discussion: Increasing the nickel concentration in soil decreased the dry weight of root and shoot, and this decrease was significant in both inoculated and non-inoculated plants at Ni250 treatment (p≤0.05). Plants inoculated with AM fungus showed significantly higher height and dry weight of shoots than plants without inoculation (p≤0.05), but the effect of mycorrhizal inoculation on the dry weight of roots was not statistically significant. The effect of nickel on the colonization percentage of roots and easily extractable Bradford-reactive soil glomalin (EE-BRSG) was significant. EE-BRSG was higher at all levels of nickel in inoculated plants than in non-inoculated ones. Moreover, with the increase of nickel concentration in soil up to 100 mg Kg-1, total Bradford reactive soil glomalin (T-BRSG) increased. The concentration of phosphorus in the shoots and roots of inoculated plants was higher than in non-inoculated plants. Mycorrhizal inoculation significantly increased the concentration of zinc and copper in the aerial part. Moreover, nickel treatment did not show a statistically significant effect on the concentration of copper in the aerial part and iron in the roots. Inoculation with AM fungus showed a significant impact on the nickel concentration of the shoots and roots, and the concentration of nickel in the roots of inoculated plants at Ni250 level was significantly higher than plants without inoculation by 29% (p<0.05). Mycorrhizal plants had lower nickel concentrations in the aerial part at Ni100 and Ni250 by 30% and 33% respectively, compared to the NM plants. The translocation factors in inoculated plants at Ni100 and Ni250 levels were significantly lower than that in non-inoculated plants, which indicates the role of fungi in preventing the transfer of nickel to the aerial parts and its accumulation in the roots. Moreover, inoculated plants in the Ni100 and Ni250 treatments showed a significantly lower bio-concentration factor by 36% and 22%, respectively, compared to non-inoculated plants.Conclusion: The results showed that AM colonization can help to reduce the toxicity of nickel by increasing plant growth and uptake of phosphorus, zinc and copper. AM colonization had a prominent impact in preventing the nickel transfer to the aerial parts and its accumulation in the roots. It seems that AM fungi can be used for phytostabilization of heavy metals in soils.
Soil Biology, Biochemistry and Biotechnology
Mahboobeh Abolhasani Zeraatkar; Ahmad Tajabadi Pour
Abstract
Introduction: Plants are usually exposed to a wide variety of abiotic stresses which can seriously inhibit plant growth and development. To address this, numerous strategies have been proposed and used by researchers, including increased irrigation rounds, cultivation of salinity- and drought-resistant ...
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Introduction: Plants are usually exposed to a wide variety of abiotic stresses which can seriously inhibit plant growth and development. To address this, numerous strategies have been proposed and used by researchers, including increased irrigation rounds, cultivation of salinity- and drought-resistant genetically modified crops (GMO crops), and application of plant-growth-promoting rhizobacteria (PGPRs). PGPRs can act as an efficacious, long-lasting, and crucial option to ameliorate the negative impacts of abiotic stresses in crops. Plant growth promoting rhizobacteria can serve as key in sustainable agriculture by improving soil fertility, plant tolerance, crop productivity, and maintaining a balanced nutrient cycling. Consequently, search for new strains of PGPR for biofertilizer and development of microbial diversity map for any region is helpful. Hence, the present study investigates the effect of native salinity-resistant PGPRs on the physiological and biochemical characteristics and productivity of alfalfa plants in soil under salinity stress.Materials and Methods: The present study was based on a completely randomized factorial design. The experiments were conducted on alfalfa plants (Bami variety) in four repetitions and under two levels of salinity (control and 200 mM sodium chloride and calcium chloride) with five strains of PGPRs from Sinorhizobium meliloti sp., two positive controls (i.e., 20 mg/kg of phosphorus and 70 mg/kg of nitrogen fertilizers), two negative controls (i.e., no fertilizer and no bacteria), and two treatments (including positive control and negative control). Growth parameters (dry weight of aerial parts, roots, and nodules), osmolytes (reducing sugars, soluble proteins, and proline), uptake of K+ and K+/Na+ ratio, and concentration of malondialdehyde (MDA) in alfalfa plants in non-saline and saline soils were measured at the end of 60-day experiments.Results and Discussion: The analysis of variance (ANOVA) results revealed a significant effect of salinity on the dry weight of aerial parts and roots, the weight and number of nodes in each pot, the K+/Na+ ratio in roots and aerial parts, and the concentration of reducing sugars, proline, MDA, and soluble proteins in the aerial parts. The effect of PGPRs was also found to be significant on all the above traits. Under no salinity stress and compared to negative control plants, the dry weight of aerial parts in plants inoculated with superior PGPRs (SM89, SM16, and SM65) was raised by 2.3, 1.9, and 1.8 folds, while this increase in plants inoculated with mild (SM73) and weak (SM21) PGPRs was 1.4 and 1.2 folds, respectively. Under salinity stress (200 mM NaCl and CaCl2) and compared to negative control plants, the increase in dry weight of aerial parts of plants inoculated with superior PGPRs (SM89, SM16, and SM65) was increased by 4.2, 4, and 2.1 folds, while this increase in plants inoculated with mild (SM73) and weak (SM21) PGPRs was raised by 1.7 and 1.2 folds, respectively. Despite a drop in the growth of aerial parts in plants under salinity, salinity-resistant PGPRs were able to significantly enhance the growth of aerial parts of plants in saline conditions compared to the controls (receiving no fertilizer and PGPRs). Salinity stress reduced other growth parameters, the rate of K+ uptake, and the K+/Na+ ratio, while it contrarily increased the concentration of reducing sugars, soluble proteins, proline, Na+, and MDA in plants. Inoculation of alfalfa plants with two superior PGPRs (SM89 and SM16) was found to significantly improve growth parameters, uptake of K+, osmolytes, and K+/Na+ ratio in alfalfa plants under non-saline conditions and salt stress, compared to control plants (not inoculated with PGPRs and receiving no fertilizer). Ultimately, each inoculation of plants with all three superior PGPRs reduced the concentration of MDA and Na+ in alfalfa plants.Conclusion: Experiments on the biochemical and physiological plant–PGPR interactions revealed that plant responses to stresses are largely controlled by microbial communication. PGPRs can trigger systemic resistance in plants through their metabolites, which function as extracellular signals, thereby enabling plants to survive under abiotic stresses. In the present study, microbial inoculation was found to significantly improve the physiological functioning of the plants. The results revealed that adding native salinity-resistant PGPRs to the soil can diminish the negative effects of salinity stress on alfalfa plants. Likewise, inoculation and enrichment of the plant's rhizosphere with beneficial and resistant microbiomes were efficient for sustaining the growth of plants under abiotic stresses such as salinity.
Soil Biology, Biochemistry and Biotechnology
Marzieh Mazraeh; Roya Zalaghi; Naiemeh Enayatizamir
Abstract
Introduction Growth-stimulating bacteria are now proposed as an alternative to chemical fertilizers in order to increase soil fertility in sustainable agriculture. Biofertilizers are also expressed as microbial inoculants that are capable of removing soil nutrients from an inaccessible state through ...
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Introduction Growth-stimulating bacteria are now proposed as an alternative to chemical fertilizers in order to increase soil fertility in sustainable agriculture. Biofertilizers are also expressed as microbial inoculants that are capable of removing soil nutrients from an inaccessible state through biological processes. Plant Growth Promoting Bacteria (PGPRs) refer to a broad group of susceptible bacteria, which grow alongside the plant as the host and stimulate plant growth. On the other hand, these microorganisms in the soil are able to stimulate and improve biological indicators, such as microbial carbon biomass, microbial respiration, and microbial yield, and may also affect different forms of carbon in the soil. Among the PGPRs, it is possible to refer to Enterobacter and Pseudomonas. Pseudomonas are bacteria present in all agro-soils and have different growth-promoting characteristics. Enterobacteriaceae family is a large group of bacteria that are naturally present in the water, soil, and materials that are corrupted and contaminated. To evaluate the biological changes of soil due to the activity of PGPRs, biochemical parameters (microbial respiration and microbial carbon biomass) are usually monitored in the plant's rhizosphere. The rhizobox is one of the tools used to study the changes in the rhizosphere, by limiting the roots in a certain volume of soil and facilitating the sampling of rhizosphere soil. The aim of this study was to investigate the effect of plant growth-promoting bacteria on some biological and chemical properties of the soil under Rhizobox conditions. Materials and Methods In order to study some of the chemical and biological properties of the soil cultivated with maize and wheat and inoculated with growth promoting rhizobacteria (PGPR), a completely randomized design, including two maize and wheat plants and three levels of inoculation, including non-inoculated, Pseudomonas sp. strain Rhizo_9 and Enterobacter cloacae strain Rhizo_33 in three replications in Rhizobox pots was done in greenhouse conditions. At the end of the period, the plants were harvested and the dry weight of roots and shoots was measured. Also, 3 soil samples were sampled from each rhizobox, as follows: rhizosphere 1 (soil clinging to the root), rhizosphere 2 (1 cm soil clinging to mesh), and non-rhizosphere (soil far from the mesh). Some soil characteristics, including basal respiration, substrate induced respiration, metabolic quotient, and soil carbon components (soil organic carbon, microbial carbon biomass, cold-water-soluble carbon, hot-water-soluble carbon, and permanganate oxidable carbon) were measured. Results and Discussion Results showed that the amount of each carbon component, as well as basal and substrate-induced respiration in treatments with bacteria, was higher than non-bacterial treatments and these biological properties in the soil cultivated with maize were higher than those under wheat cultivation. According to the results, the highest amounts of the basal respiration (0.31 mg CO2 g-1 day-1), the substrate-induced respiration (1.65 mg CO2 g-1 day-1), the permanganate oxidable carbon (213.1 mg kg-1), and the microbial carbon biomass (17.53 mg 100g-1) were related to rhizosphere 1 soil of maize inoculated with Pseudomonas. The highest amounts of the organic carbon (0.82%), the cold-water-soluble carbon (1727 mg kg -1), and the hot-water-soluble carbon (955 mg kg-1) were related to rhizosphere 1 soil in maize inoculated with Enterobacter. This could show the differences between two bacteria in affecting on different forms of carbon in the soil. Conclusion The results of this study showed that maize had a higher effect on carbon forms of soil that could be because of higher root biomass and probably higher root secretions of maize in comparison to wheat. Also, by increasing the distance from plant roots (from rhizosphere1 soil to bulk soil), different forms of carbon decreased that showed the impact of rhizosphere (plant roots and rhizospheric microorganisms) on physicochemical and biological characteristics.Inoculation of PGPR bacteria caused an increase in soil respiration and soil different carbon forms but the two bacteria were different in increasing various forms of soil carbon that seems to be related to different secretions or different effects of bacteria or plant-bacteria associate on soil carbon forms. Although inoculation of Pseudomonas resulted in a higher amount of microbial carbon biomass, inoculation of Enterobacter resulted in higher amounts of cold-water-soluble carbon, hot-water-soluble carbon, and soil organic carbon. Also, the application of two PGPR bacteria (Enterobacter was more effective) increased root and shoot dry weights of maize and wheat compared to non-bacterial treatments.
Soil Biology, Biochemistry and Biotechnology
Maryam Talebi Atouei; mohsen olamaee; REZA GHORBANI NASRABADI; seyed alireza movahedi Naeini
Abstract
Introduction Salinity is the most important challenge in arid and semi-arid regions. Salt stress, ionic and osmotic components, like other abiotic stresses, lead to oxidative stress that damage cellular membranes, nucleic acids, oxidizing proteins, and causing lipid peroxidation through overproduction ...
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Introduction Salinity is the most important challenge in arid and semi-arid regions. Salt stress, ionic and osmotic components, like other abiotic stresses, lead to oxidative stress that damage cellular membranes, nucleic acids, oxidizing proteins, and causing lipid peroxidation through overproduction of reactive oxygen species (ROS). Antioxidant capacities and osmolytes play a vital role in protecting plants from salinity that causes oxidative damages. Applying biological methods such as using of halotolerant plant growth promoting rhizobacteria (PGPR) is very important to reducing the harmful effects of salinity on plants. Also exopolysaccharide production by plant growth-promoting strains helps in binding cations, including Na+, and thus decreases the content of Na+ available for plant uptake. This is especially useful for alleviating saline stress in plants. Biochar can also alleviate the negative impacts of salt stress in crops. Biochar can enhance plant growth either by its direct or indirect mechanisms of actions. The direct growth promotion relates to supplying mineral nutrients, such as Ca, Mg, P, K and S etc., to the plant, whereas, indirect mechanisms involve improving soil physical, chemical and biological characteristics. Materials and Methods In this research, the effect of halotolerant plant growth promoting bacteria, biochar and gypsum was investigated on enzymatic and non-enzymatic defense mechanisms of barley such as Catalase, Superoxide Dismutase, Proline and Membrane stability under salinity stress. The experiments were carried out as a factoria with a completely randomize design in greenhouse conditions for 2016-2017. The factors included: bacteria (without inoculation (T0), bacterial isolate T5 (megaterium Bacillus), bacterial isolate T17 (licheniformis Bacillus ), biochar (0 and 5percent w/w), gypsum ( 0and 50 percent gypsum requirement ) and soil leaching (without and leaching with) with three replications. The activity of catalase (CAT) was determined by changes in absorbance at 240 nm (IUg−1FW) (Aeby, 1984). Superoxide dismutase (SOD) activity was determined by nitroblue tetrazolium (NBT) reduction, according to Minami and Yoshikawa (1979) and the enzyme activity was expressed as (IUg−1FW). Proline content was estimated according to Bates et al., (1973) and expressed as µ mol g−1 fresh weight (FW). Membrane stability was estimated according to Sairam and. Saxena (2001). All statistical analyses were performed using SAS software. The means of different treatments were compared using LSD (P ≤0.05) test. Results and Discussion The results showed that using halotolerant bacteria and biochar reduced the activity of antioxidant enzymes in barley plants. This reduction was higher in the treatment containing bacteria T17 (Bacillus licheniformis) biochar and with leaching. Also, inoculated plants with both bacteria had the highest concentration of proline, which was significantly higher in the treatment containing bacteria T17 (Bacillus licheniformis) biochar and gypsum. Also, application of halotolerant bacteria, biochar and gypsum improved the membrane stability of plant. This increase has been remarkable in inoculated treatments with T17 bacteria (Bacillus licheniformi) in saline soil with leaching associated with 50 percent gypsum requirement Conclusion Generally, results showed that halotolerant bacteria, biochar and gypsum can be used as a tool for reducing adverse effects of salt stress. Inoculation of soil with these bacteria has helped in alleviating saline stress by changing several physiological, enzymatic, and biochemical agents in plant. Bio-remediation of salt affected soils is one of the cheap and eco-friendly approaches for remediation of salt affected lands as the traditional physical and chemical techniques are becoming costly. The plant growth promoting halotolerant bacteria helps in Bio-remediation of salt affected soils and thereby improving the agricultural crop yields. Incorporation of biochar into salt-affected soil could diminish salinity stress by decreasing soil bulk density, increasing in soil cation exchange capacity, potassium and calcium concentrations, water holding capacity and nutrient and water availability in soil. Also, bichar due to high organic matter content can play a dramatic role in salt affected soil with organic compound defficiency. According to these amended features of biochar in soil, we suggest, more experiments conducted by biochar with different material and ratios under saline - sodic soils.
Soil Biology, Biochemistry and Biotechnology
Naeimeh Enayatizamir; A Moezzi; Shila Khajavi
Abstract
Introduction Biosurfactants or microbial surfactants are surface active molecules that are produced from a variety of microorganisms. Due to its amphiphilic nature, these biomolecules are capable of lowering the surface tension, interfacial tension and forming micro-emulsion to enable mixing of two immiscible ...
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Introduction Biosurfactants or microbial surfactants are surface active molecules that are produced from a variety of microorganisms. Due to its amphiphilic nature, these biomolecules are capable of lowering the surface tension, interfacial tension and forming micro-emulsion to enable mixing of two immiscible solutions. Such properties exhibit excellent detergency, emulsifying, foaming and dispersing traits, which can be applied in various industries. The features that make them commercially promising alternatives to chemically synthesized surfactants are their lower toxicity, higher biodegradability, better foaming properties, and greater stability towards temperature and pH. Limited full scale production has been realized for many biosurfactants due to expensive raw material, low production yield and high purification cost. In order to alleviate these problems, many studies have been carried out using cost-free or low-cost feed stocks or agricultural byproducts as substrates for biosurfactant production. Oil pollution and remediation technology has become a global phenomenon of increasing importance. Materials and Methods In this study, Potential strains of microorganism were isolated from various hydrocarbon polluted area on nutrient agar medium using sterile saline (0.85% NaCl) method and different bacterial isolates were selected based on the colony morphology on nutrient agar. The selected isolates were screened for the production of biosurfactants using following screening methods. Pure culture of bacterial isolates were streaked on the freshly prepared blood agar and incubated at 37°C for 48-72 h. Results were recorded based on the type of clear zone observed i.e. α-hemolysis when the colony was surrounded by greenish zone, β-hemolysis when the colony was surrounded by a clear white zone and γ-hemolysis when there was no change in the medium surrounding the colony. Surface tension reduction and emulsification index of isolates was determined by culturing the isolates in minimal mineral salt solution containing glucose as carbon source. Based on the screening test results, the positive isolates were inoculated into the mineral salt medium for the biosurfactant production and then identified by its microscopic appearance, biochemical tests based on Bergey’s manual of determinative bacteriology and molecular method. Bio-surfactant production by superior isolate was evaluated in minimal mineral salt medium containing different carbon sources (kerosene, sugar cane molasses, phenanthrane and glucose) at 30 and 37 °C within the incubation periods of 48 and 156 hours. Emulsification activity, oil spreading, drop collapse, cell hydrophobicity and surface tension activity of isolate were used to detect biosurfactant production. Results and Discussion Out of 13 isolates of microorganism, strain S10 showed positive response to biosurfactant tests (hemolytic activity, surface tension reduction and emulsification index) and was select for identification and considering the effect of different carbon sources on its biosurfactant production. The biochemical and molecular identification results showed isolate S10 belongs to Bacillus pumilus. Results showed that Bacillus pumilus was able to grow in all carbon sources. Based on bio-surfactant production, this strain had a positive or β hemolysis on blood agar medium. Results showed that this bacterium was able to grow in all carbon sources. The compound produced by this strain in each of carbon sources at both temperatures (30 and 37 °C) and incubation periods (48 and 156 hours) collapsed down. The maximum surface tension reduction was recorded in the samples containing molasses as carbon source incubated at 30 ° C for 48 hours, in which bacterium reduced surface tension to 20.33 mNm-1. The highest bacterial growth with a higher surface tension reduction selected this isolate as a potential biosurfactant producing microorganism. The maximum emulsifying and cell hydrophobicity were also recorded in molasses (28%) and kerosene (70%) respectively. Conclusion In conclusion, the study represented surfactant activity of the bacterial strain isolated from oil contaminated soils. This confirms that environment has an influence on the metabolism of the tested microbes. This study suggests that, Bacillus pumilus isolated from oil contaminated soil showed biosurfactant producing ability. Further study on the utilization of agro industrial wastes as substrates for the large-scale production of biosurfactants is recommended.
Soil Biology, Biochemistry and Biotechnology
S. A. Hosseini; mhsen olamaee; S. A. Movahedi Naeini; F. Khormali; R. Ghorbani Nasrabadi
Abstract
Introduction Potassium is one of the essential and macro elements in the growth of plant cells. This element plays an important role in improving the quality of agricultural products. The amounts of available potassium levels in most soils decrease more quickly and potassium balance is disturbed in many ...
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Introduction Potassium is one of the essential and macro elements in the growth of plant cells. This element plays an important role in improving the quality of agricultural products. The amounts of available potassium levels in most soils decrease more quickly and potassium balance is disturbed in many fields. Cultivation and lack of the application of potassium fertilizers in agricultural soils of Iran have caused the depletion of potassium and the amount of available potassium in most soils has reached below the critical level. The compensation of depleted potassium in the soil through indigenous resources and use of potassium bio-fertilizers is therefore very important. Weathering of silicate minerals by bacteria is considered as one of the essential K source for plant growth and development. The objective of this study was to isolate and identify potassium solubilizing bacteria from the shale containing glauconite mineral in Golestan Province and determine some traits related to plant growth promotion and selecting a superior strain in order to incubate in wheat lands. Materials and Methods Accordingly, a total of 5 samples 1 kg of rhizosphere of wheat from a depth of 0 to 30 cm and 5 samples 1 kg from shale stone (containing glauconite) were collected from Aitamir formation in Golestan Province in May 2015 and were transferred to the laboratory of Gorgan University of Agricultural Science and Natural Resources. Isolates were transferred to Aleksandrov media containing glauconite and muscovite and incubated for 10 days and the isolated strains were stored in the refrigerator at 4 oC. The amount of potassium release in solutions after 10 days was measured. Some biochemical and morphological properties of isolates were determined based on standard methods. PGPR tests were done in the isolates which were morphologically different and had high potential in releasing K. Finally, a strain whith high ability in releasing potassium and growth promoting properties was identified using nucleotide sequence of 16S rRNA gene. Results and Discussion Results showed that 40 strains from the first stage, 20 strains from rhizospherial soil and 20 strains from the soil resulting from glauconite mineral powders were isolated. Biochemical and potassium release tests showed that the highest released potassium was related to isolate No. 39 with an amount of 34.2 mg l-1 in muscovite, and 31.8 mg. l-1 in glauconite. The amount of siderophore produced in the superior strains showed that the lowest and the highest ratios of the diameter of the colony, were 1.12 and 3.1 related to isolate No. 19 and No. 39, respectively. The highest and the lowest auxins produced were also related to the isolate No. 39 and No. 27 with the amount of 52.25 and 5.15 mg per liter, respectively, measured at 72 and 96 hours. The results showed that the soluble phosphorus between different isolates was significantly different (P <0.05), its greatest concentration at 72 hours was related to isolates No. 39 with an amount of 295 mg per liter and the lowest at 24 hours was related to isolate No. 31 with an amount of 80 mg per liter. Also, the production of hydrogen cyanide test showed that none of the isolates was capable of producing siderophore. The obtained results from nucleotide sequence of 16S rRNA gene showed that the selected strain belonged to Arthrobacter phenanthrenivoran species. Conclusion It can be concluded that silicate bacteria contribute to the dynamics and mineralizing of elements in the soil and eventually K release from glauconite containing shale minerals mainly by reducing rhizosphere pH, the secretion of organic anions and complex formation with the surface cations of mineral and secreted extracellular Polysaccharides and soluble compounds and decomposition of soil organic matter. Among 40 isolated strains and the various tests and the results of released potassium in both minerals, the results showed that the potential of potassium releasing was different between the tested strains. Moreover, this study showed that in addition to the effect of these strains on potassium releasing, siderophore production, auxin and inorganic phosphate solubility, they can be effective in plant growth and in land inoculation. This study revealed the potential of indigenous bacteria species in the release of K from shale containing glauconite. It is anticipated that shale containing glauconite can provide a part of the need of the crops for potassium.
Soil Biology, Biochemistry and Biotechnology
Majid Baghernejad
Abstract
Abstract Introduction Drought stress is one of the important environmental factors that limit distribution and productivity of major crops. Drought stress caused by reducing the availability of external water, which makes reduces the ability of the plant’s roots to take up nutrients and induced ...
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Abstract Introduction Drought stress is one of the important environmental factors that limit distribution and productivity of major crops. Drought stress caused by reducing the availability of external water, which makes reduces the ability of the plant’s roots to take up nutrients and induced cellular and photo-oxidative damages, through the increased accumulations of reactive oxygen species. Plant growth promoting rhizobacteria and arbuscular mycorrhizal fungi by using different mechanisms such as production of siderophores, organic acids, proton, growth regulators, and other chelating agents, and creative of reductive conditions, increase dissolution of minerals and mobility of non-soluble nutrients and thus improve nutrients uptake and yield of plants. They can influence plant root morphology and change the quantity and quality of root exudates. Mycorrhizal symbiosis involves a complex interaction among plant, soil and mycorrhizal fungi. Arbuscular mycorrhizal associations' relationship are rather important in crops because they are believed to increase nutrients uptake, improve plant fitness, and plant water relations and thus increase the drought resistance of host plants. Plant growth promoting rhizobacteria improve water relations of plants in part due to increases of plant growth, nutrient uptake and antioxidant activities. Maize is an effective host of arbuscular mycorrhiza in infertile and drought conditions and its root system consists of different root types. Therefore, the objectives of this study was to evaluate the effects of Glomus intraradices, Pseudomonas fluorescens (as a PGPR bacterium) and drought stress on growth characteristics and micro-nutrients uptake of maize in a calcareous soil under maize cultivation. Materials and Methods A greenhouse experiment in a factorial completely randomized design was conducted to evaluate the effects of arbuscular mycorrhizal (AM) fungus (Glomus intraradices), Pseudomonas fluorescence, and drought stress on root colonization and absorption of micro-nutrients (Fe, Mn, Zn, Cu) by maize (Zea mays). The factors were consisted of arbuscular mycorrhizal fungus at two levels: G0 (not inoculated with fungus) and G1 ( inoculated with Glomus intraradices), bacteria at two levels: B0 (not inoculated with bacterium) and B1 (inoculated with Pseudomonas fluorescence) and drought stress at four levels: S0 (without stress), S1 (75% FC), S2 (50% FC) and S3 (25% FC). Mycorrhizal inoculum was prepared through the trap culture of forage sorghum (Sorghum biocolor L.) with spore of Glomus intraradices. The potential of inoculum (spore numbers of 12 g-1 substrates and root colonization of 80%) was measured for spore extraction and counting, and evaluation of root colonization. The bacterium used in the present experiment was Pseudomonas fluorescens and provided by soil biology and biotechnology laboratory of College University of Agriculture and Natural Resources of Tehran University, Karaj, Iran. The bacterium had a high ability to dissolve poorly soluble organic and inorganic phosphate compounds, to produce siderophores, indole acetic acid (IAA), and 1-aminocyclopropane-1-carboxylate (ACC)-deaminase enzyme. A non-sterile composite soil sample was collected from depth of 0-30 cm soil surface of Agriculture Research Station of Shiraz University, Shiraz, Iran (fine, mixed, mesic, Calcixerollic Xerochrept). The samples were air-dried and passed through a 2mm sieve. Some physical and chemical properties of studied soil are measured. The seeds were inoculated with 1mL fresh and active suspension of bacterium (population of 1×108 colony-forming units (CFU) per milliliter). After a growth period of 4 months, plant materials harvested and data were subjected to analysis of variance and means were compared by least significant difference. Results and Discussion In non microbial treatments, wet and dry weights of shoot significantly decreased whereas other measured parameters had not significant changes under drought stress of 25% FC. At each level of drought stress, root colonization significantly higher in mycorrhizal treatments than non mycorrhizal treatments. The highest root colonization percent was observed in treatments of co-inoculation of plant with both inoculants. Co-inoculation of plant with both inoculants significantly increased morphological properties and shoot nutrients uptake except Fe uptake in comparison with non microbial treatments up to drought stress of 50% FC. Conclusion All measured parameters ( leaf area, wet and dry weights of root, root colonization, shoot micronutrient uptake) except wet and dry weights of shoot significantly decreased with increasing of drought stress up to 25% of FC. Single and co-application of bacterium and fungus decreased the negative effects of drought stress under low levels of water stress. Root colonization significantly increased with single application of fungus and co-inoculation of plant with fungus and bacterium. Co-application of fungus and bactrieum increased shoot nutrients uptake except Fe uptake up to 50% FC in comparison with non inoculated treatments.
Soil Biology, Biochemistry and Biotechnology
M. Soliemanzadeh; H. Khademi; M. Sepehri
Volume 37, Issue 2 , March 2015, , Pages 59-72
Abstract
Microorganisms play an important role in providing nutrients for plants and also in soil development. This study was carried out to investigate the effect of two strains of Bacillus cereus on the release of potassium and iron from micaceous minerals. An experiment was set up with a completely randomized ...
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Microorganisms play an important role in providing nutrients for plants and also in soil development. This study was carried out to investigate the effect of two strains of Bacillus cereus on the release of potassium and iron from micaceous minerals. An experiment was set up with a completely randomized design and factorial arrangement with three replications. Treatments included two types of mineral (phlogopite and muscovite), two strains of bacteria (PTCC 1247 and PTCC 1665), control and eight time periods. The results indicated that released potassium and iron were highly dependent on the strain of bacterium and also the mineral type. Strain PTCC 1665 could release a higher amount of potassium as compared to PTCC 1247. The amount of released iron increased at the beginning of the experiment but decreased and then increased as time passed. In general, the amount of released iron from phlogopite was higher than that from muscovite.
Soil Biology, Biochemistry and Biotechnology
A.R. Fallah Nosratabad; S. Momeni; S. Shariati
Volume 37, Issue 2 , March 2015, , Pages 73-86
Abstract
The present investigation was designed to compare the effect of combination biofertilizer of nitrogen fixing free-living bacteria and plant growth promoting bacteria of Azotobacter. It also aimed to compare the effect of Azospirillum alone and in combination with other plant growth promoting bacteria ...
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The present investigation was designed to compare the effect of combination biofertilizer of nitrogen fixing free-living bacteria and plant growth promoting bacteria of Azotobacter. It also aimed to compare the effect of Azospirillum alone and in combination with other plant growth promoting bacteria of Pseudomonas fluorescens and Bacillus subtilis with five nitrogen fertilizer levels on the wheat growth indices and yield.The experiment including biofertilizer and different amounts of nitrogen fertilizer was carried out as factorial in completely randomized design with three replications. At the end of plant growth period, some plant indices such as spike and grain number, crop yield, grain to straw weight ratio, straw yield, and grain nitrogen percentage were measured. The results showed that in the simple effect of bio fertilizer, the most effective factor was related to the biofertilizer consortium containing Azotobacter, Azosprillum, Pseudomonas and Baillus subtilis which respectively increased 8, 22.5, 26.5 and 23.3 % the amounts of grain nitrogen, spike number, straw yield and plant yield in comparison with control treatment. Although in the simple effect of chemical fertilizer on studied indices, 100 kg/ha of nitrogen had the most effect, it didn’t demonstrate any significant difference in comparison with the fertilizer level of 75 kg/ha. The highest amounts of measured indices were related to the interaction of bio fertilizer including Azotobacter, Azosprillum, and Pseudomonas and Bacillus subtilis with nitrogen level of 75kg/ha that could respectively increase 25, 100.4, 53.5, 100.6 and 92.6% of grain and spike number, the nitrogen content of grain, straw and plant yield compared to control plant.
Soil Biology, Biochemistry and Biotechnology
S. Shariati; H. Alikhani; A. Pourbabaei; F. Shariati
Volume 37, Issue 1 , September 2014, , Pages 93-107
Abstract
In order to determine the effect of plant growth promoting bacteria Pseudomonas fluorescens on yield and nutrient availability in corn some special materials like mesoporous silica nanoparticles, vermicompost, bentonite and a mixture of all were inoculated by the bacteria and preserved for six months. ...
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In order to determine the effect of plant growth promoting bacteria Pseudomonas fluorescens on yield and nutrient availability in corn some special materials like mesoporous silica nanoparticles, vermicompost, bentonite and a mixture of all were inoculated by the bacteria and preserved for six months. Soil and seeds were treated by the inoculants. The experiment was set up in a randomized complete block design with three replications. The treatments comprised of three inoculants and two fertilizers including diammonium phosphate, single super phosphate and control (without any phosphorus fertilizer). After 60 days of corn emergence, some plant growth indices and the concentration of some elements in plant shoots were measured. The results demonstrated that Pseudomonas fluorescens inoculant significantly increased phosphorus shoot content, total yield and chlorophyll by 74, 46 and 22.1%, respectively compared to the control treatment (P<0.05), but it did not show any significant difference with phosphorus fertilizer treatments (P>0.05). The vermicompost inoculants could significantly (P<0.05) increase zinc and iron contents of shoots by 114 and 53.6%, respectively in comparison to the control treatment. Orthogonal comparisons of the two methods of seed and soil inoculation showed the efficiency of seed inoculation on shoot phosphorus at 5% level, but no significant difference was observed between these two methods for other measured characteristics (P>0.05).
