دکتر حسینعلی علیخانی

Periphyton is a complex biological community comprising microorganisms and organisms from different physiological groups that collectively attach to various submerged surfaces in wetland ecosystems. Periphytic biofilms play a critical role in the wetland ecosystem’s dynamicity and possess a considerable capacity for decontamination. The following article examines the various aspects of periphytic biofilms’ capacity for removing some of the most critical environmental pollutants, including organic pollutants, pharmaceuticals, heavy metals, microplastics, and excess nutrients. The paper provides comprehensive discussions on the critical pollutant removal mechanisms employed by the periphytic communities. Additionally, the paper endeavors to contribute to the available knowledge regarding utilizing and developing periphyton-derived bioremediation technologies by presenting the most recent research findings, discussing common challenges in periphyton’s biotechnological application, and delineating crucial research gaps to postulate future research questions. Applying periphyton in pollutant removal aligns with the most recent paradigm of bioremediation technologies advocating the use of microbial consortia instead of single microbial species. In this regard, research results convey that the simultaneous presence of multiple microbial groups together in a biological community (such as periphyton) increases the microorganisms’ resistance to unfavorable environmental conditions and enhances the biological community’s capacity for decontamination. Based on the studies presented in this article, periphytic biological communities can employ different mechanisms to transform and biodegrade a wide array of pollutants.

Traditionally, most researches on artificial wetlands focuses only on two phases, i.e., water and soil, ignoring or underestimating the importance of the microbial aggregates between them, the third phase in artificial wetlands. Filamentous algae grow substantially by attaching themselves to the soil/sediment surface and form aggregates with bacteria, fungi, and other micro- and meso-organisms (e.g., protozoa and metazoa), known as periphytic biofilms. Actually, periphytic biofilms are ubiquitous in wetlands (including paddy fields) and play a major role in regulating nutrient cycling in these ecosystems. However, their effects on rice plant growth indices have been rarely reported. Therefore, the aim of this study was to investigate the effect of natural periphyton and enriched periphyton with plant growth-promoting microorganisms on germination and rice growth indices.

To achieve the objectives of this study, first three periphyton samples were collected from paddy fields of Guilan province and grown in BG11 medium in the laboratory. Then, the superior bacteria and fungi that stimulated plant growth were isolated from the periphyton mass and the periphyton samples were enriched with these microorganisms. The greenhouse experiment was conducted in 1399 in the research greenhouse of the Department of Soil Science and Engineering, University of Tehran. For this purpose, 2.5 kg pots with a length of 25 cm and a diameter of 15 cm were selected for greenhouse experiments. Twenty rice seeds (Oryza Sativa: cultivar Hashemi) were placed directly in pots in three replications for each treatment. About 100 mL of natural periphyton suspension grown in BG11 medium (equivalent to 2 g/kg dry weight) and periphyton enriched with superior bacteria and fungi and a mixture of bacteria + fungi was added to the pots. Experimental treatments included WP treatment:  without periphyton, PN1 epipelon 13, PN2 epiphyton 8 and PN3 epipelon 6, PN1 + Bacillus cereus, PN2 + Talaromyces stipitatus and PN3 +Acinetobacter calcoaceticus + Talaromyces minioluteus. Also, phosphorus fertilizer treatment at four levels (F0: without phosphorus fertilizer, F1: supply of 50% of phosphorus fertilizer from mono calcium phosphate source, F2: supply of 100% of mono calcium phosphate and F3: supply of 100% of rock phosphate source) was added to the pots. The treatments were grown in three replications in a greenhouse with a temperature between 25–35 °C for 30 days in 80 percent humidity.

The results showed that the presence of natural and enriched periphyton in the soil increased the germination index of rice seeds compared to the control by about 1.4 and 1.9 times, respectively. The rice seedlings decreased by about 10 percent with the presence of natural periphyton, but this negative effect was lowered by enrichment of plant growth promoting microorganisms. Measurement of rice seedling height index showed that the highest measured height was related to the treatment of periphyton enriched with Bacillus cereus (PSB) at F2 level of 39 cm. In general, in natural periphyton treatments, about 15 percent of the height of rice shoots was lower than the control treatment and periphyton treatments enriched with superior microorganisms. The maximum measured root length was related to the treatment of recombinant periphyton with Bacillus cereu (PSB) with 16.95 cm. The lowest root length was measured in natural periphyton treatment (PN3) with 11.5 cm. The highest shoot to root ratio was related to periphyton treatment enriched with Bacillus cereus at F2 and F3 fertilizer levels with 0.7 and 0.68, respectively, with a statistically significant difference at level 95 percentage (p˂ 0.05) compared to other treatments. The maximum weight of rice biomass in periphyton enriched with Bacillus cereus (PSB) treatment, which was the enriched with plant growth promoting bacterium, was measured at F2 and F3 fertilizer levels with 8.7 and 8.3 g, respectively. In general, measurement of rice seedling height, root length, biomass weight and phosphorus in shoots showed that treatment of enriched periphyton with Bacillus cereus at different levels of phosphorus fertilizer had a positive effect and led to an increase of 3.5, 9.4, 6.1, and 35.8 percent compared to the control treatment, respectively.

Finally, it can be concluded that periphyton enriched with superior plant growth microorganisms can be used as a multi-functional biofertilizer in paddy fields, it increases plant growth and efficiency of fertilizer, and it can also control weeds in paddy fields.

Today, in order to increase the efficiency of fertilizer use and reduce environmental pollution, the production and consumption of slow-release fertilizers is considered. The objective of the current study was to apply three methods of rotary drum (A), insitu hydrogel synthesis (B) and two-stage (C) to reduce the solubility rate of urea fertilizer using starch as a cheap and environmentally friendly source and evaluation the comparative efficiency of these samples on the growth and nutritional responses of tomatoes. At first, fertilizers were synthesized in three methods. Then, the effects of synthesized samples (A,B and C) were compared with un-coated urea granules on morphological characteristics of tomatoes. A factorial based on completely randomized blocks design were utilized with three replications in 2020 in greenhouse conditions, at 180 and 420 kg/ha of each fertilizer treatment. The results showed that urea release rate after 6 hours from synthesized (A, B and C) fertilizers was reduced 87.33, 32.08 and 29.22%, respectively compared to un-coated urea. Comparison of coating methods showed that the highest amount of dry weight (roots and shoots), stem length, chlorophyll content and number of leaves and lateral branches were observed in C fertilizer treatment. Nitrogen use efficiency and apparent nitrogen recovery in C fertilizer treatment increased 36.54 and 27.04% compared to urea, respectively. The use of starch as a natural biopolymer in the structure of these fertilizers reduces nitrogen loss and environmental pollution.

Periphyton is a biological layer that is widely present in flood plains such as paddy fields and plays an important role in the nutrient cycle in such ecosystems. The role of this biological layer in dissolving and absorbing insoluble phosphorus in the country's paddy fields has not been recognized so far. This study was performed in the research laboratory of the department of soil science and engineering, university of Tehran in 2020 to investigate the role of periphyton grown in paddy fields of Guilan province in the release and absorption of phosphorus. For this purpose, 20 paddy fields in Guilan province were sampled from epipelon (LON) and epiphyton (TON). The results showed that about 68% of the population of autotrophic components in epipelon and epiphyton samples belonged to Chlorella and Chlorococcum. The genera Lyngbya, Scenedesmus, Nostoc and Navicula were the most abundant in the next ranks. The results of phosphate dissolution showed that samples of LON 6 and 13 and TON 8 have the highest solubility of phosphorus. Phosphorus uptake capacity was also very high in LON 6 and 13 samples and increased by 1840 and 2000% compared to the initial biomass, respectively. This amount was 825 percent in the TON 8. The results also showed that epipelon samples showed a higher ability than epiphyton samples in terms of phosphorus absorption and retention. In general, the results of this study showed that the periphytic biofilm has a high ability to absorb phosphorus, which reduces the waste of fertilizer used and therefore helps to increase its efficiency, and thus reduces non-point pollution.

To date, no research has been done on the role of periphyton in paddy fields, especially on phosphate solubilizing ability of bacteria and fungi isolated from the biofilm. The aim of this study was to investigate the phosphate solubilizing ability and some other plant growth promoting (PGP) traits of bacteria and fungi isolated from the periphyton sampled from 20 paddy fields in Guilan province. In this study, 44 bacterial isolates and 32 fungal isolates capable of solubilizing phosphate were isolated. Among the microbial isolates, effective 10 bacterial isolates and 5 fungal isolates were selected for additional tests. The results showed that bacterial isolates 13B25 and 6B11, with the highest phosphate solubilization, solubilized 354 and 327.3 mg P l-1, respectively. The ability to produce siderophore (based on HD / CD index) by isolate 13B25 and 6B11 was equal to 3.2 and 3.4, respectively, with a significant increase (p < 0.001) compared to other isolates. The production of indole-3-acetic acid by the isolates 13B25 and 6B11 was 175.3 and 205.7 μg ml-1, respectively. Among the fungal isolates, two isolates, 6F11 and 8F12, were the best in PGP traits. The solubilization content of phosphorus by these two fungal isolates was 742 and 818 mg l-1, respectively. The results of molecular identification of effective bacterial isolates showed that 13B25 and 6B11 were most similar to Bacillus cereus and Acinetobacter calcoaceticus, respectively. In addition, fungal isolates 6F9 and 8F12 were most similar to Talaromyces minioluteu and Talaromyces stipitatus, respectively.

Phthalic acid esters are synthetic compounds used as emollients in polymer and plastic compounds. The entry of these compounds into the environment and the human food cycle and the development of a variety of cancers has raised global concerns. The purpose of this research was to investigate the concentration of phthalic acid esters (PAEs) in the soil exposed to the leachate (landfill) and finding a microbial consortium capable of the degradation of these pollutants. The concentration of phthalic acid esters in the soil was measured by the ultrasonic method and GC-MS. The results showed that the concentration of diethyl hexyl phthalate (DEHP) in soil (4.52 mg/Kg) was 6 times that of its international standard (0.7 mg/Kg). Microbial enrichment was performed in a mineral salt medium containing phthalic acid esters (30 o C and 120 rpm) and a microbial consortium capable of degrading phthalic acid esters was isolated. To investigate the biodegradation of phthalic acid esters by consortium, the residual phthalate concentration was extracted with ethyl acetate and measured by GC-MS. The results showed that the this consortium was able to degrade more than 96% of low molecular weight phthalates of dimethyl phthalate, diethyl phthalate and dibutyl phthalate (medium molecular weight phthalate) (30 o C and 120 rpm). In the case of DEHP (the world's most widely used plasticizer), the consortium was able to degrade it by 55% at 400 mg/L. Besides, phthalic acid esters separately were degraded almost completely by this consortium (5 days incubation, 30 oC, 120 rpm). Our results demonstrate the biodegradation of phthalic acid esters by this consortium and recommend its use for bioremediation of phthalates in contaminated soils.

There are hardships in oil-polluted soil remediation that are increased by factors, such as soil salinity and pollution age. This study aimed to evaluate the effect of the native strain of Rhodococcus bacterium and organic waste on the the total petroleum hydrocarbons reduction in contaminated saline soil by crude oil in incubation condition. For this purpose, a full factorial experiment using a completely randomized design was conducted with four factors: bacterial inoculation of Rhodococcus cercidiphylli Y1M65003, 5% spent mushroom compost, 5% sugarcane bagasse, and addition nitrogen and phosphorus with 100: 10: 1 ratio from urea and superphosphate triple. The analysis of variance of total petroleum hydrocarbons elimination showed that all four factors could significantly affect (p

The use of biofertilizers such as plant growth-promoting bacteria to reduce damage caused by water-deficit stress in plants and improve physiological factors and thus increase plant growth in arid and semi-arid regions is an essential management to control water-deficit stress. Therefore, this study was conducted to investigate the simultaneous effect of different levels of water-deficit stress and inoculation of plant growth-promoting bacteria on some physiological traits of Brant's Oak )Quercus brantii L.) seedlings.

In order to investigate the effect of plant growth-promoting bacteria and different levels of irrigation on some physiological traits of oak) Quercus brantii L.) seedlings, an experiment was conducted in a complete randomized design with five replications in the research greenhouse of Yazd University. The main factor was three irrigation levels (80 % of full irrigation as control, 60 and 40 % of full irrigation) and the sub-factor was six levels of plant growth promoting bacteria (no inoculation as control and seed inoculation with Bacillus anthracis, B. licheniformis, Stenotrophomonas maltophilia, B. cereus and BMix (combination of 4 strains().

The results of analysis of variance showed a significant effect of water deficit stress levels, bacterial treatments and their interaction on all studied traits. The results of comparison of means showed that the amount of chlorophyll a, b and total chlorophyll decreases with increasing levels of water-deficit. In contrast, the amount of proline, total phenol and percentage of free radical scavenging in oak seedlings under stress increased significantly compared to the control sample. The accumulation of malondialdehyde (MDA) that shows the rate of degradation and peroxidation of membrane lipids were significantly increased by water-deficit treatments, while application of PGPRs caused reduction in malondialdehyde content. These results showed that PGPRs can reduce negative effects on lipids peroxidation and thus increases the resistance of seedlings to water-deficit stress conditions.

In general, among the bacterial treatments, (BMix) bacterial treatment increased chlorophyll a and b, total chlorophyll and decreased malondialdehyde and Bacillus anthracis bacterial treatment increased proline, total phenol and percentage of free radical scavenging under water-deficit severe stress.

Today, the use of chemical fertilizers to increase agricultural production has created many environmental problems. In addition, environmental stresses are one of the most important factors reducing crop yield and production. Given the importance of rice plants in ensuring food security nationally and globally and increasing the price of chemical fertilizers, it is necessary to find eco-friendly routes for sustainable agriculture. The use of biofertilizers is the most worthy way to reduce the use of chemical fertilizers and improve plant resistance in rice fields. Azotobacter has been used as a biofertilizer for over a century and has been well studied on a laboratory and field scale. Azotobacter have also been reported as nitrogen-fixing bacteria in the rhizosphere and roots (endophytically) of rice. In this study, the effect of Azotobacter biofertilizer as a plant growth-promoting rhizobacteria, on rice and the mechanisms of this effect were investigated. The results showed that this bacterium produces phytohormones and stimulants of plant growth and fix atmospheric nitrogen in the rhizosphere and as an endophyte in rice. In addition to nitrogen fixation, this bacterium increases plant growth indices, nutrient uptake, and grain yield of rice by dissolving insoluble phosphates, producing indole acetic acid, hydrogen cyanide, siderophore. Also, the use of Azotobacter inoculant in acute salinity conditions increased the concentration of proline, malondialdehyde, ACC-deaminase enzyme, and some hormones in the plant, which increased the resistance of rice to this stress. Considering the positive effect of using Azotobacter inoculant as a biofertilizer on rice plants and the effect of this bacterium on reducing the consumption of nitrogen fertilizers, preparation of biofertilizers containing native bacteria of Azotobacter and their application in rice fields is recommended.

In order to investigate the effect of plant growth promoting rhizo-bacteria (PGPRs) and humic acid on some morphological and physiological characteristics of marshmallow (Altheae officinalis L.) a pot experiment was carried out under greenhouse condition at Faculty of Agriculture, University of Birjand, in 2017. The experiment was conducted using a complete randomized blocks design based on factorial arrangement with three replications. First factor was seed inoculation with strains of Pseudomonas fluorescence bacteria at four levels (non- inoculation, inoculation with strains 51, 79 and 163) and second factor was humic acid at four levels (0, 150, 300 and 450 mg/kg soil). Results showed that Pseudomonas fluorescence strains and humic acid had significant effects on morphological and physiological measured traits. The most effects of inoculation created by strain 163 of Pseudomonas fluorescenss bacteria and it increased leaf dry weight, leaf area, leaf chlorophyll index, carotenoids and protoin leaf compare to control. The result also showed that increasing of humic acid concentration up to 150 mg/kg of soil increased, leaf area, leaf chlorophylls index, chlorophyll fluorescence index and protein leaf compare to control. Combination use of Pseudomonas fluorescenss bacteria (strain 163) and humic acid (150 mg/kg soil) had the most effect on increasing of leaf fresh weight, leaf area, chlorophyll a, chlorophyll b, total chlorophyll, carotenoids and phosphor leaf compare to control. Due to these results, application of biological fertilizers containing Pseudomonas fluorescence and humic acid can improve morphological and physiological characteristics of marshmallow.

Plant growth promoting rhizobacteria with ACC deaminase activity can be applied for stimulating plant growth under tension situations. In the present study, bacterial isolates were isolated from wheat rhizosphere in three provinces of Zanjan, Kurdistan and Hamedan and then screened for ACC deaminase production and salinity tolerance. Six isolates out of 167 isolates were able to degrade ACC to alpha-keto-butyrate and ammonia and the K78 isolate was selected as superior isolate. A completely randomized design with factorial arrangement was carried out on wheat plant in a greenhouse experiment. Experimental factors include: five salinity levels (1.3, 8, 12, 14, and 16 dS.m-1), three bacterial inoculation levels (no inoculation (B0), inoculation with salinity-resistant isolate and ACC deaminase production capacity (B1), inoculation with salinity-resistant isolate without ACC deaminase production capacity (B2). The results showed that salinity had a significant and negative effects on growth and nutrient uptake and decreased shoot length. The K78 isolate increased shoot length (21.5 %) and potassium uptake (15 %) significantly compare to B0 treatment but had no significant effect on sodium uptake. Overall, it can be concluded that inoculation of K78 isolate can reduce the negative effects of salinity on growth indices and the nutritional conditions of wheat.

Periphytons are the most important microorganism communities which can be found almost in all aquatic systems. Periphytons play important roles in ecological functions of an ecosystem. They are composed of multilayered consortia of photoautotrophs (e.g. unicellular and filamentous cyanobacteria, benthic diatoms and green microalgae) and heterotrophs (bacteria, fungi and protozoa). Due to the role of periphytons in the processes of nitrogen fixation and dissolution of insoluble phosphorus and potassium, Samples of sediment, water and periphytons collected and investigated from three lagoons in Fashtam, Tazesel and Qalewersel in Guilan province. Results showed that Chlorophyta, Bacillariophyta and Cyanobacteria constituted 26.24%, 56.06% and 17.69% of the periphyton components in Qalewersel lagoon, respectively. In the Fashtam lagoon, the Chlorophyta, Charophyta, Euglenozoa, Ochrophyta, Bacillariophyta, and cyanobacteria species formed 38.48%, 20.58%, 1.72%, 1.74%, 19.68% and 19.52% of the periphyton components, respectively. Also, in the Tazesel lagoon, Chlorophyta, Euglenozoa, Bacillariophyta and Cyanobacteria constituted about 13.93%, 0.56%, 51.9% and 33.6% of components of periphyton, respectively.

A significant part of the nitrogen fertilizers due to the high solubility in water, penetrates into the lower parts of the soil and become unavailable to the plant. To prevent nitrogen losses, various methods have been used, of which coatings is the most widely used methods to reduce the rate of dissolution in water. The objective of the current study was to produce novel slow release fertilizers (SRFs) using starch-based polymer nanocomposites (in terms of environmental compatibility and degradability) and to investigate the comparative efficiency of these samples on the growth and nutritional responses of tomatoes. Firstly, two formulations of urea fertilizer coated with starch-based polymer nanocomposite reinforced with biochar nanoparticles (A) and pristine polymer without nanoparticles (B) were synthesized. Then, the effects of two levels (180 and 420 kg/ha or 60 and 140 mg/kg) synthesized SRF samples (A and B) and un-coated urea granule fertilizer (as a control) on morphological characteristics of tomatoes were investigated. A factorial design based on the completely randomized blocks with three replications was performed at Agricultural Biotechnology Research Institute, Karaj. The results showed that the presence of nanoparticles increases the release time of urea from the coating layer, and it was prolonged with increasing the amount of NCNPs because of favorable interfacial polymer-filler interactions. So that, the nitrogen release rate from sample A, at pH= 2, 6 and 10, was respectively decreased 49.46, 18.52 and 45.13% as compared to sample B. Moreover, application of SRF samples increased nitrogen use efficiency, nitrogen agronomic efficiency and apparent nitrogen recovery. So that, the nitrogen use efficiency in fertilizer treatments A and B with usage of 420 kg/ha was respectively increased 7/85 and 14/68% compared to urea fertilizer.

Periphyton or periphytic biofilms are microbiomes consisting of a complex matrix including autotrophic and heterotrophic types such as algae, bacteria, fungi, protozoa, metazoa, etc. Periphytic biofilms are commonly found in many aquatic ecosystems such as the sea, lakes, rivers, streams, ponds and paddy fields and play an important role in primary production, food network interactions such as carbon cycle, phosphorus and some other nutrients. Periphytic biofilms respond quickly to environmental changes, especially nutrients and light, and can be used as an indicator of disturbances and adverse conditions in aquatic ecosystems. In recent years, research interests in using periphyton for controljng the non-point source pollution, treating contaminated water, and interferencing nutrient have increased. Although the effects of periphyton on water quality and its relationship to water flows have been investigated by researchers, our understanding of their function in paddy fields and their effect on nutrient cycles is limited. In the present article, an attempt has been made to present a summary of the research done on periphyton and their effect on the nutrient cycle, especially on rice plants' growth in paddy fields.

The present study was carried out to investigate the effects of biological and chemical fertilizers on morpho-physiological characteristics and nutrients uptake in tomato plant (Lycopersicon esculentum Mill). A factorial trial arranged in a completely randomized design was carried out under greenhouse conditions. Treatments consisted of five levels of  chemical fertilizers applied as: control (F0), fertilizer traditionally used (F1), soil-test-based optimum nutrients levels (F2), commercial root stimulant (F3), optimum nutrients levels + application of N, P, Zn and Si by the rate of twofold of the optimum levels (F4) and five levels of  biological fertilizers including: control (BF0), PGPR (BF1), arbuscular mycorrhiza fungi (BF2), vermicompost (BF3), and biological package (BF4).The results indicated that the interaction effect of treatments was significant only for shoot dry weight. F4-BF4 and F2-BF4 treatments increased shoot dry weight up to 122% and 121% compared to the control (F0-BF0), respectively. The application of BF4 incresed the leaf area 55% and the application of F4 increased SPAD chlorophyll index 29% as compared to the control and they were the best for increasing such properties.  Among the biological treatments, the application of BF4 increased the uptake of N, P, K and Si in the shoot by 108.4, 224.7, 115.6 and 226.3%, respectively, and among the chemical treatments, the application of F4 increased the uptake of these elements by 58.7%, 14.9% 25.1% and 158% in comparison with control, respectively. The results of this study showed that in the soils with high pH, the nutrients uptake of tomato plant can be effectively improved via integrated application of vermicompot and chemical fertilizers under both optimum and even higher levels.

Stresses of drought, salinity and deficiency of nutrients especially phosphorus (P) are the most important challenges for wheat production in Iran. One of the ways to achieve more wheat yield production is increasing of this plants tolerance to stresses of water-deficit, salinity and deficiency of essential elements such as P; and/or alleviate destructive effects of these stresses. In this respect, use of PGPR can be useful. Research has shown that PGPR with multiple mechanisms reduces the negative effects of water-deficit and salinity stresses, and also increases the resistance of plants to these stresses, which ultimately leads to increase of plants growth. This study was designed and carried out to investigate the effect of three superior PGPR on qualitative and quantitative indices of wheat under water-deficit stress in saline soil.

The soil used in this experiment was collected from longitude of 49° 26' 25'' E, latitude of 35° 52' 26'' N and elevation of 1534 m (located in the Qazvin province of Iran) from depth of 0-30 cm of soil. According to the experimental design, 3.5 kg of soil with applying P-fertilizers treatments was filled to the pots. The factorial arrangement based on completely randomized design (CRD) was used in this study. The treatments were replicated three times. The first factor: soil water content at two levels including 80% and 55% FC (W80 and W55); the second factor: Bacterial inoculants at four levels including control or non-inoculated seeds with bacterium (B0), inoculated seeds with Bacillus pumilus strain W72 (B1), inoculated seeds with B. safensis strain W73 (B2), inoculated seeds with Staphylococcus succinus strain R12N2 (B3); and the third factor: P-fertilizers at six levels including control or non-treated plants with P-fertilizers (F0), and plants treated with (rock phosphate) RP - (F1), RP + 19 mg triple superphosphate (TSP) / kg of soil (F2), RP + 38 mg TSP / kg of soil (F3), RP + 57 mg TSP / kg of soil (F4), with 57 mg TSP / kg of soil (F5), generally there were 144 experimental units (pots). Also, 192 mg RP (containing 13.8% P2O5 or 6.13% P) was mixed per kg of soil in each of RP treatments. Statistical analysis of data was performed using SAS software and comparison of means was evaluated by using the Tukey's test (HSD) at p < 0.05 level. There were 5 plants in each pot and irrigated up to 80% FC with distilled water. With the beginning of stem elongation stage, water-deficit stress was applied and continued until the harvest. During the experiment, pots were kept in greenhouse at 25/20±2°C day/night temperatures and 16 h photoperiod with 23,000 lux light intensity. At the end of the experiment, plants height, fertile clusters, root dry weight /shoot dry weight ratio, total dry weight of plant, grain number, thousand grain weight, also, root, shoot and grain P-concentration were measured.

Generally, it can be said that the moisture level of W80 compared to W55 increased all of measured traits in wheat plant. Due to the unique properties of water and its role in biological and non-biological reactions, by reducing soil water content to near of the permanent wilting point (W55), water absorption by the plant hardly occurs. Therefore, the plant needs to consume more energy for water absorption or grow with less water than normal status, which these factors disturb the metabolism of cells and eventually decreases natural activity and growth of plant. Also, it seems that under water stress condition, wheat plant by formation of “Rhizosheaths” around of their own roots, enters to the defensive phase and by this strategy prevents expansion of their own rhizosphere. With attention to the special importance of the rhizosphere in the supply of water, nutrients and activity of microorganisms, as well as the effect of microorganisms secretion and root exudates on the solubility and availability of nutrients. Thus, it is reasonable that qualitative and quantitative traits of plants decrease by reduction of the rhizosphere diameter due to the water-deficit stress. There was no significant difference between application of rock phosphate and control (F0) for most of measured traits of soil and plant; but, application of RP with bacterial treatments (B1 and B2 at W80 and B3 at both level of W55 and W80) compared to the control, often increased measured traits. Also, each level of TSP compared to the control, often increased this trait. Research indicates that RP can be used as a P-fertilizer, but its efficiency depends on its reactivity in the soil. There is ample evidence that RP has not enough efficiency in neutral and alkaline soils; but, it can be used as the P-fertilizer with proper efficiency in acidic soils or alkaline soil with application of PGPR. Often, all of three bacterial treatments (B1, B2 and B3) at level of W80 and B3 treatment at level of W55, compared to control (without bacterial inoculation) improved qualitative and quantitative traits of plant. Research also shows that under stressful and non-stressful conditions, PGPR can improve plant growth by different strategies. However, this microorganism does not always improve plant growth under all conditions. It seems to be due to differences in genetic and function of bacteria and with conditions change, each bacterium may behave differently. Conclusions In general, for wheat cultivation that may get exposed to moisture stress at one or more stages of its growth (such as dry-farming of wheat), the use of B3 bacterial inoculant (Staphylococcus succinus strain R12N2) seems appropriate for crop management. Because in this study at both W80 (non-water-deficit stress) and W55 (severe water-deficit stress) levels of soil water content, B3 treatment increased qualitative and quantitative of wheat traits. In other words, because of the natural conditions of the dryland farming, the probability of precipitation is different; it seems that B3 treatment can increase wheat production under these conditions. However, the use of this bacterium as a biofertilizer for dryland wheat farming in Iran or other place of the world requires further testing and evaluation in dryland farms of that countries.

The present study investigates the potential of rhizosphere and endophytic bacterial isolates isolated from the roots of wheat plant in terms of plant growth promoting (PGP) traits and their effect on the wheat yield and decreased phosphorus (P) fertilizer use. To this end, the isolated bacteria have been first screened for the production of indole-3-acetic acid (IAA) in the presence of tryptophan in the culture medium, and then the bacteria have been tested for their ability to dissolve inorganic and organic phosphates. In further laboratory studies, a factorial experiment has been conducted as a randomized complete block design with three replications over two-year field study (2017 and 2018). Experimental treatments include biological and chemical phosphorus fertilizer, the former with two levels (with and without bacterial inoculation) and latter (as the second factor) from triple super phosphate source with five (0%, 25%, 50%, 75%, and 100% of the full recommended fertilizer rate). Results from this experiment prove that supplementing 75% of the recommended P-fertilizer rate with bacterial isolates (co-inoculation with rhizospheric and endophytic bacteria) increases wheat growth indices and yield (747.40 g m-2), which are statistically equivalent to the full fertilizer rate without them. Based on these results, it is suggested that biofertilizer can be used as a fertilizer supplement to reduce the level of fertilizer use but cannot be a substitute for phosphorus fertilizer.

Currently, the excessive application of chemical fertilizers in agriculture field is under debate due to environmental concerns. Therefore, it is important to find the alternative strategies to reduce harmful effects of farming practices. Aims of the research was to investigate the potential of rhizosphere and endophytic bacterial isolates isolated from the roots of wheat plant in terms of plant growth promoting (PGP) traits and study their effect on the wheat plant growth indices and decreased phosphorus (P) fertilizer use. To this end, the isolated bacteria were first screened for the production of indole-3-acetic acid (IAA) in the presence of tryptophan in the culture medium, and then the bacteria were tested for their ability to dissolve inorganic and organic phosphates. Then, the ability of these bacteria to improve wheat plant growth was conducted in a completely randomized design under greenhouse condition. Rhizospheric isolate R185 and endophyte isolate E240 produced 299.2 and 330.1 μg / ml P respectively and also produced 19.2 and 22 μg / ml IAA, respectively. 16S rRNA sequencing showed that these bacterial isolates were Pseudomonas. The results obtained from pot assay showed that the combined use of the strains caused a significant increase in wheat growth and nutritional indices (an increase of 55.6% in the amount of plant P) compared to their single application (35.6 and 36.4% increase in plant P content by R185 and E240, respectively). Among the cultivars evaluated, Roshan cultivar had a higher percentage of P (4.7%) and biomass (14.2%) than Marvdasht cultivar.

Despite the abundance of iron in the earth's crust and soil, this nutrient is not usually available for plants in calcareous soil with high pH. In the present study four superior isolates with alternative physiological traits (No. 3, 8, 20 and 23) isolated from 10 soil samples for producing siderophore and their contribution in solubilizing insoluble iron-containing compounds in calcareous soil were evaluated. Results showed that in spite of higher halo diameter to colony diameter of isolate No. 23 in CAS agar medium (3.46mm) at soil incubation test, DTPA-extractable iron using isolates No. 3 and 20 was greater than the ones in isolate No. 23 as 10.7 and 14.67 percent, respectively. Greatest amount of DTPA-extractable iron in the soil sample was obtained during 40-days incubation. Molecular test showed that isolate 20 was 99 percent similar to the strain Bacillus Sporothernodurans. Biochemical tests also revealed that isolate 8 probably belong to Entrobacteriaceae family and isolates 3 and 23 belong to Pseudomonas Genus.

Today, groundwater contamination has become a major environmental issue around the world. Petroleum products affect groundwater quality at many sites across the country. It mainly results from leaking or seeping of products from storage tanks or transferring pipes. These products are typically multicomponent organic mixtures composed of chemicals with varying degrees of water solubility. Many of the petroleum products are amenable to biological degradation in the aqueous phase by naturally occurring microorganisms in the subsurface. To create and maintain conditions that are conductive to microbial activity within the contaminated aqueous-phase is the main focus of this research. BTEX was selected as the petroleum contaminant to be used in a laboratory experiment. A two-dimensional sand tank was built and BTEX was injected into the sand at top of the unsaturated zone. In order to simulate the behaviour of the bacteria and to predict the long-term remediation program, RT3D model with double Monod algorithm was selected. The comparison of the observed data in laboratory experiment with simulated results showed that the calibrated model can simulate the BTEX movement and biodegradation, satisfactory. Using the calibrated model indicated that complete remediation would occur after three months with biodegradation and 27 months without biodegradation. This proved that how important is the biodegradation in long-term remediation projects. In addition, the proposed methodology in this research for isolating the bacteria and remediation was successful and can be proposed to be implemented in larger scale.

Drought, salinity and essential plant nutrient stresses especially phosphorus (P) are the most important challenges for wheat production in dryland farming of Iran. The objective of this study was to investigate the effect of three plant growth promoting bacteria strains on soil available-P, as well as some of the physiological and growth traits of wheat under water-deficit stress. For this purpose, a pot experiment was carried out as factorial arrangement with three factors including: water deficit stress at two levels, application of P-fertilizer at six levels and strains of plant growth promoting bacteria at four levels, based on completely randomized design (CRD) with three replications within 125 days. The results show at the water deficit stress of 55% field capacity (FC) and without P-fertilizer application, bacterial treatment of Staphylococcus succinus compared to control increased available-P, P-uptake of root and grain by 2.4, 4.9 and 2.7 times respectively. At moisture treatment of 80% FC and without P-fertilizer application, treatments of Bacillus pumilus, B.safensis and S. succinus compared to control, increased available-P by 1.6, 1.6 and 1.6 times; P-uptake of root by 3.1, 3.1 and 2.9 times; P-uptake of grain by 2.2, 2.4 and 2.2 times, respectively. Maximum dry weight of root, shoot and grain (5.3, 18.2 and 4.6 g pot-1, respectively) were obtained at the maximum level of P-fertilizer treatment (F4). At the water deficit stress of 55% FC, bacterial treatment of S. succinus compared to control increased prolin, root dry weight, grain dry weight and P-uptake of shoot up to 8, 31.9, 20.4 and 25.5 percent, respectively. Generally, the use of Staphylococcus succinus strain R12N2 seems to be appropriate for increasing wheat production in dryland farming.

The soil microbial community affects its fertility through the decomposition, mineralization, storage, and release of nutrients. Given the release of about 20-30% of photosynthetic materials in the rhizosphere, this environment has provided favorable conditions for the presence of microbial populations.

The aim of this study was to investigate the potential of rhizosphere and endophytic bacterial isolates isolated from the roots of wheat plant in terms of plant growth promoting (PGP) traits to identify their 16S rRNA sequences. To this end, the isolated bacteria were first screened for the production of indole-3-acetic acid (IAA) in the presence of tryptophan in the culture medium, and then they were tested for their ability to dissolve inorganic and organic phosphates. In the next step, other growth promoting factors including siderophore production and ACC-deaminase were investigated.

Among the isolates obtained from rhizosphere and intra-root of wheats, 15 rhizosphere and 7 endophyte isolates were selected based on their ability to induce growth promoting properties. A total of 7 isolates belonged to the Bacillus, 4 isolates to Pseudomonas, 2 isolates to Staphylococcus, 2 isolates to Paenibacillus, and the rest belonged to the genera Sphingobacterium, Lysinibacillus, Advenella, Enterobacter, Variovorax, and Plantibacter.

According to the obtained results, the dominant genera among the rhizosphere and endophyte isolates were Pseudomonas and Bacillus. Increased yield through increased nutrient bioavailability is the result of siderophore production, dissolution of insoluble inorganic and mineral phosphates, the production of growth factors and plant growth hormones, especially indole acetic acid, which can increase crop growth indices and yield. It also has to protect the environment and the plant.