نوع مقاله : مقالات پژوهشی
نویسندگان
دانشگاه ارومیه
چکیده
باکتری های افزاینده رشد گیاه (PGPR) و قارچ ریشه های آربوسکولار (AMF) سبب بهبود رشد گیاهان در تنش های محیطی میشوند. در این پژوهش نقش برخی گونه هایPGPR (ترکیبی از گونه های Pseudomonas شامل سویه های P. fluorescens ، P.putida و P. aeruginosa) و AMF (ترکیبی از گونه های Glomus شامل G. mosseae، G. intraradices و G. fasciculatum) بر برخی عناصر و همچنین برخی شاخص های فیزیولوژیک، توسط گیاه خارزن بابا (Onopordon acanthium L) بررسی شد. این مطالعه در شرایط گلخانهای به صورت فاکتوریل با دو فاکتور غلظت کادمیم (صفر، 10، 30 و 100 میلی گرم کادمیم بر کیلوگرم) و تیمار تلقیح میکروبی، در قالب طرح پایه بلوک های کامل تصادفی انجام شد. نتایج نشان داد که با افزایش غلظت کادمیم در خاک رشد گیاه، غلظت آهن، روی و مس در شاخساره، مقادیر کلروفیلها و کاروتنوئیدها، ارتفاع، تنفس میکروبی و محتوای نسبی آب برگ (RWC) کاهش و مقادیر غلظت کادمیم در گیاه به طور معنی داری (05/0P≤) افزایش یافت. مایه زنی میکروبی سبب کاهش تاثیر نامطلوب کادمیم بر رشد گیاه شد. عملکرد شاخساره گیاه به طور میانگین در تیمارهای PGPRو AMFبه ترتیب بیش از 1/2 و 7/2 و تنفس میکروبی به ترتیب بیش از 17/2 و 01/2 برابر تیمارهای مشابه شاهد بود. چنین نتیجه گیری میگردد که مایه زنی میکروبی سبب افزایش بردباری گیاه و کاهش تاثیر نامطلوب کادمیم بر رشد گیاه می شود.
کلیدواژهها
عنوان مقاله [English]
Influence of PGPR Bacteria and Arbuscular Mycorrhizal Fungi on Growth and some Physiological Parameters of Onopordon acanthium in a Cd-Contaminated Soil
نویسندگان [English]
- MirHassan Rasouli-Sadaghiani
- Habib Khodaverdiloo
- Mohsen Barin
- Solmaz Kazemalilou
Urmia University
چکیده [English]
Introduction: Heavy metals (HMs) are serious threat for environment due to their dangerous effects. These metals as contaminants that can be accumulated in soil and after absorption by plants, finally will be found in food chains. Cadmium (Cd) is one of the dangerous HMs that threats the health of plants, living organisms and human. Physicochemical remediation methods may cause large changes in different characteristics of soils . Recently environmental-friendly strategies including phytoremediation have been emphasized by researchers. Phytoremediation that refers to the use of plants and their assistance with microorganisms for remediation of contaminated soils is an effective and low cost method for reclamation of heavy metals polluted soils. The most important limitation of phytoremediation is low availability of heavy metals and sensitivity of plants to contamination. There are evidences that soil microbes can help to overcome these limitations through several ways. Plant growth promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) are known to enhance plant growth and survival in heavy metal contaminated soils through different mechanisms including producing promoting metabolites, auxin, siderophore and antibiotics. In this study the role of some strains of PGPR (a mixture of Pseudomonas species including P. putida, P. fluorescens, and P. aeruginosa) and AMF (a mixture of Glomus species including G. intraradices, G. mosseae and G. fasciculatum), on uptake and accumulation of Cd, Fe, Zn and Cu as well as some physiological properties of Onopordon (Onopordon acanthium L) were evaluated.
Materials and Methods:This study was carried out under greenhouse condition as a factorial experiment based on a randomized complete block design with two factors including Cd concentration (four levels) and microbial treatment (three levels) in three replications. Consequently, a soil was selected and spiked uniformly with different concentrations of Cd (0, 10, 30 and 100 mg Cd kg-1 soil) at greenhouse of agricultural college in Urmia University. The contaminated soils were then sterilized and subsequently inoculated with arbuscular mycorrhizal fungi (a mixture of Glomose species including G. intraradices, G. mosseae and G. fasciculatum) and plant growth promoting rhizobacteria (a mixture of Pseudomonas species includeing P. putida, P. fluorescens, and P. aeruginosa). The seeds of Onopordon plants were grown in 2.5 kilogram pots under greenhouse condition. At the end of growing season the shoot dry weight, Cd, Fe, Zn and Cu concentration and element contents and some of physiological parameters of plant as well as microbial properties were analyzed. Furthermore, the effect of soil Pb level on population, activity and efficiency of the inoculated microbes was studied.
Results and Discussion: Significant difference was observed for plants’ dry weights. At different Cd levels, the yield of inoculated plants was higher than that of control plants. Furthermore, at elevated Cd concentration, plant height, biomass, relative yield, chlorophyll a, b, carotenoids, relative water content (RWC) decreased significantly (P < 0.05), however, plants inoculated with plant growth promoting rhizobacteria and arbuscular mycorrhizal fungi showed considerable amount of dry matter, chlorophyll a, b as well as RWC. Mycorrizal and bacterial inoculation and Cd treatment also had significant effect on leaf photosynthetic pigments concentration and plant relative water content. In general, concentrations of photosynthetic pigments and RWC were higher in inoculated plants at every level of soil Cd. The microbial inoculation effectively decreased the inhibitory effects of Cd on plant growth. Shoot yield of arbuscular mycorrhizal fungi and plant growth promoting rhizobacteria plants increased by 2.7 and 2.1 times as well as microbial respiration increased by 2.17 and 2.01 times compared to control treatment. The results showed inoculated plant absorbed more Cd than non-inoculated plants. Plant growth promoting rhizobacteria were more effective than arbuscular mycorrhizal fungi inoculation in shoot Cd concentration. Cd contamination reduced soil microbial population and basal respiration. Results showed that with increasing soil Cd concentration shoot Fe, Zn and Cu concentrations significantly decreased. Root colonization rates decreased significantly with 10 mg kg-1 Cd addition for AMF treatments, and drastically with 100 mg kg-1 Cd added. Plant roots in the control and PGPR treatment were not colonized.
Conclusion: It is concluded that plant growth promoting rhizobacteria and arbuscular mycorrhizal fungi inoculation could be sustained and promoted plant growth in phytoremediation processes. Therefore, under Cd contamination it can be use PGPR and AMF as growth promoters and finally enhance phytoremediation efficiency.
کلیدواژهها [English]
- Cd Toxicity
- Heavy metals
- Microbial Inoculation
- Onopordon acanthium
- Physiological Properties
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