گیاه‌پالایی سرب در حضور تلقیح جداگانه و هم‌زمان کرم خاکی، قارچ‌های میکوریزا و ریزوباکتر‌ها در ذرت

نوع مقاله: مقاله پژوهشی

نویسندگان

1 گروه خاک شناسی، دانشکده کشاورزی، دانشگاه شهرکرد

2 گروه خاکشناسی دانشگاه شهرکرد

3 دانشگاه شهرکرد

چکیده

سابقه و هدف:خاک ممکن است به‌طور طبیعی ازجمله نزدیکی به مواد معدنی و سنگ معدن و فعالیت‌های صنعتی بشر با غلظت بالایی از فلزات سنگین آلوده شود.سرب (Pb)،معمولاً مسبب آلودگی خاک است و عامل کاهش قابل‌توجه فعالیت زیستی خاک در نظر گرفته می‌شود.گیاه‌پالایی فن‌آوری نوظهور و کم‌هزینه‌ای است که با بهره‌گیری از گیاهان و موجودات زنده باعث حذف، تبدیل یا تثبیت آلاینده‌ها در آب، رسوبات و یا خاک می‌شود. بنابراین موفقیت گیاه‌پالایی به اثر متقابل بین ریز/درشت جانداران و ریشه گیاهان در ریزوسفر بستگی دارد.هدف این پژوهش بررسی پیامد مایه‌زنی جداگانه و هم-زمان کرم خاکی قارچ و باکتری بر قابلیت دسترسی و استخراج و یا تثبیت عنصر سرب توسط گیاه ذرت در خاک آلوده به سرب با اندازه گیری غلظت و جذب سرب در اندام هوایی و زیرزمینی گیاه می‌باشد.
مواد و روش‌ها: خاک آلوده از منطقه معدن سرب باما واقع در جنوب غربی اصفهان جمع‌آوری شد. بذر ذرت، پس از استریل سطحی و جوانه‌زنی، به گلدان‌های حاوی 4 کیلوگرم خاک آلوده به سرب (استریل شده در دمای oC 121 به مدت 2ساعت) منتقل شدند.آزمایش در قالب طرح کاملاً تصادفی با آرایش فاکتوریل(2×2×2) انجام شد.فاکتور‌ها شامل 1) کرم خاکی (بدون کرم و با کرم خاکی ایزینیا فتیدا (Eisenia foetida))، 2) قارچ میکوریزا (بدون قارچ و با قارچ میکوریزا (ترکیبی از Funneliformis mosseae و Septoglomus constrictum)) و 3) باکتری (بدون باکتری و با باکتری (ترکیبی از Bacillus sp.و Bacillus licheniformis)). پس از گذشت 3ماه از دوره رشد تحت شرایط گلخانه، اندام هوایی ذرت از سطح خاک جدا شد. ریشه و اندام هوایی به‌طور جداگانه به‌منظور تعیین غلظت سرب هوا‌خشک، توزین و آسیاب شدند. به‌منظور عصاره‌گیری سرب ریشه و اندام هوایی از روش خاکستر استفاده شد و توسط دستگاه جذب اتمی اندازه‌گیری شد. غلظت سرب خاک با روش DTPA-TEA اندازه‌گیری شد. فاکتور‌های تجمع زیستی، انتقال و اصلاح برای هر تیمار محاسبه شد.
یافته‌ها:به طور‌کلی تلقیح گیاه با این جانداران، وزن خشک ریشه و اندام هوایی، سرب قابل دسترس خاک، جذب سرب و فاکتور‌های تجمع زیستی و اصلاح سرب را افزایش داد. بیشترین وزن خشک اندام هوایی در تیمار‌های هم‌زمان کرم خاکی- میکوریزا و میکوریزا-باکتری با افزایش 2/3 برابری نسبت به شاهد مشاهده شد. سرب قابل دسترس خاک نیز در تیمار هم‌زمان کرم خاکی-میکوریزا-باکتری نسبت به شاهد حدود 3 برابر بیشتر بود. بیشترین مقدار جذب سرب در ریشه و اندام هوایی ذرت در تیمار همزمان کرم خاکی-میکوریزا-باکتری مشاهده شد. علاوه براین، تجمع زیستی سرب در ریشه ذرت در تمام تیمارها، به‌ویژه در تیمار میکوریزا به تنهایی، بیشتر از یک بود. اگرچه فاکتور انتقال سرب برای گیاه ذرت کمتر از یک بود، اما تنها تیمار هم‌زمان کرم خاکی و باکتری این نسبت را به بیش از یک(32/1) افزایش داد. این در حالی است که قارچ میکوریزا فاکتور انتقال را نسبت به تیمار شاهد کاهش داد. حداکثر فاکتور اصلاح سرب (14/0%)توسط ذرت با افزایش ۲۳ برابری نسبت به شاهد در تلقیح هم‌زمان کرم خاکی-میکوریزا-باکتری مشاهده شد اما به‌اندازه‌ای نبود که جهت اصلاح خاک آلوده به کار رود.
نتیجه‌گیری:با وجود افزایش قابل توجه غلظت سرب در ذرت، جذب سرب آن به اندازه ای نیست که برای استخراج عملی سرب استفاده شود. همچنین با توجه به مقادیر فاکتور‌های تجمع زیستی، انتقال و اصلاح زیستی، گیاه ذرت در فرآیند تثبیت گیاهی خاک مفیدتر بوده و بنابراین قارچ میکوریزا به‌عنوان عامل بهبود دهنده تثبیت گیاهی در افزایش رشد گیاه و همچنین ممانعت از سمیت گیاه از طریق جلوگیری از انتقال سرب به اندام هوایی مؤثر است. حضور قارچ میکوریزا موجب رشد بهتر گیاه در تیمارهای کرم خاکی و باکتری شد،به‌ویژه در شرایط طبیعی که حضور هر سه موجود زنده با یکدیگر محتمل تر است، که می‌تواند نقش بسزایی در کاهش سمیت و رشد گیاهان در مناطق آلوده داشته باشد.

کلیدواژه‌ها

عنوان مقاله [English]

Phytoremediation of Lead in the presence of individual and combined inoculation of earthworms, arbuscular mycorrhizal fungi and rhizobacteria by maize

نویسندگان [English]

  • Ali Mahohi 1
  • Fayez Raiesi 2
  • alireza Hosseinpur 3

1 Soil Science and Engineering, Faculty of Agriculture, Shahrekord University

2 Department of Soil Science, Faculty of Agriculture, Shahrekord University

3 shahrekord univecsity

چکیده [English]

Abstract
Introduction Soils may become polluted with high concentrations of heavy metals both naturally, as a result of proximity to mineral outcrops and ore bodies and anthropogenically, as a result of industrial activities. Lead (Pb), commonly caused soil pollution and considered to be responsible for significant decreases in biological activities in soils. Phytoremediation is an emerging and low cost technology that utilizes plants and associated organisms to remove, transform, or stabilize contaminants located in water, sediments, or soils. Phytostabilization focuses on the formation of a vegetation cover where sequestration (binding and sorption) processes immobilize metals within the plant rhizosphere reducing metal bioavailability. Therefore, the success of phytoremediation depends on the interactions between macro- and microorganisms and plant roots in the rhizosphere.
Materials and Methods The contaminated soil was collected from Bama mining site located in the southwest of Isfahan. After surface-sterilization and germination, maize seeds were transplanted into each plastic pot containing 4 kg of contaminated soil that already autoclaved at 121 oC for 2 h. A completely randomized design with 2×2×2 factorial treatment combinations was used with the following factors: with or without earthworm treatments (Eisenia foetida), with or without arbuscular mycorrhizal (AM) fungal treatments (co-inoculated with Funneliformis mosseae and Septoglomus constrictum) and with or without rhizobacteria (co-inoculated with Bacillus sp. and Bacillus licheniformis). After three months of growth under greenhouse conditions, maize shoots were harvested. Shoot and root were oven dried, weighed and milled used to determine Pb concentration. Concentration of Pb in roots and shoots were measured by dry ash method and soil Pb concentration was determined with DTPA-TEA method. Bioaccumulation (BF) and translocation (TF) and remediation (RF) factors for each treatment were calculated.
Results and Discussion In general, inoculation of these organisms increased plant growth, availability of Pb in soil, plant Pb concentration and bioaccumulation factor. The highest shoot dry weight was observed in earthworms-AM fungi (EM) and AM fungi-bacteria (MB) co-inoculations with 3.2 times increase compared to un-inoculated plants. Available Pb in soil in earthworm-AM fungi-bacteria co-inoculation (EMB) was about 3 times higher than un-inoculated treatments. The higher Pb uptake in maize shoot and root were recorded in EMB. Furthermore, the BF for root maize in all treatments was higher than 1, especially in AM fungal treatment, alone. Although the TF for maize was lower than 1, it was increased above 1 in polluted soil co-inoculated with earthworm and bacteria. However, AM fungi tended to decrease the TF compared to un-inoculated maize. The highest RF (0.14%) with 23 times increase compared to un-inoculated was showed in EMB treatment. Conclusions Despite the substantial enhancement of Pb concentration in the maize, Pb absorption was not high enough to achieve extraction rates which would be necessary for practical use. Furthermore, the amounts of BF, TF and RF in this study demonstrated that maize could useful for Pb phytostabilization. Hence, it appears that the presence of AM fungi (as factor improve phytostabilization) could result in a better plant growth and tolerance against Pb toxicity, when soil is co-inoculated with earthworm and/or bacteria, especially under natural conditions that the presence of these organisms' together, could reduce Pb toxicity and improve maize.

کلیدواژه‌ها [English]

  • Earthworms
  • AM fungi
  • rhizobacteria
  • Pb bioaccumulation
  • Pb translocation
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