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امکان‌سنجی جداسازی تثبیت‌کنندگان نیتروژن اتوتروفی و هتروتروفی از زیست‌لایه پریفایتون در شالیزار و بررسی اثرات آن بر رشد گیاه برنج در شرایط گلخانه‌ای | ||
| زیست شناسی خاک | ||
| مقالات آماده انتشار، پذیرفته شده، انتشار آنلاین از تاریخ 07 مهر 1404 | ||
| نوع مقاله: مقاله پژوهشی | ||
| شناسه دیجیتال (DOI): 10.22092/sbj.2025.369574.280 | ||
| نویسندگان | ||
| مهران غلامی1؛ حسینعلی علیخانی* 2؛ حسن اعتصامی1؛ زهرا کرمی1؛ محدثه شیرین زاده1؛ حمیدرضا زارع گیلدهی1 | ||
| 1گروه علوم و مهندسی خاک، دانشکدگان کشاورزی و منابع طبیعی، دانشگاه تهران | ||
| 2کرج-پردیس کشاورزی و منابع طبیعی دانشگاه تهران-گروه علوم ومهندسی خاک | ||
| چکیده | ||
| هدف از انجام این پژوهش بررسی پتانسیل زیست‌لایه پریفایتون و تثبیت‌کنندگان ساکن در آن برای تقویت تثبیت بیولوژیکی نیتروژن و بهبود حاصلخیزی خاک در شالیزارها بود. برای این منظور، نمونه‌های زیست‌لایه پریفایتونی از شالیزارهای استان گیلان جمع‌آوری شد و با تثبیت‌کنندگان جداشده از خود زیست‌لایه که در آزمون توان تثبیت نیتروژن برتر شناخته شده بودند، غنی‌سازی شدند. به مدت 40 روز در شرایط گلخانه‌ای اثر تیمارهای مختلف بر خاک و گیاه پایش گردید. نتایج نشان داد که زیست‌لایه پریفایتون پتانسیل بسیار بالایی در حاصلخیزی خاک و حمایت از رشد گیاه برنج دارد. تیمار پریفایتون‌غنی‌شده با باکتری و سیانوباکتری به طور قابل‌توجهی ویژگی‌های خاک از جمله میزان نیتروژن کل (83/37 درصد)، آمونیوم (1/42 درصد)، فسفر قابل‌جذب (35 درصد) و پتاسیم قابل‌دسترس (36/15) را افزایش داد. حاصلخیزی خاک منجر به افزایش کارایی جذب نیتروژن توسط گیاه شد. افزایش فراهمی نیتروژن در محلول خاک، افزایش در پارامترهای رشد از جمله ارتفاع گیاه، وزن خشک، میزان نیتروژن (97/3 درصد)، فسفر (18/5 درصد) و پتاسیم (21/5 درصد) در بافت گیاهچه‌های برنج را به دنبال داشت. نتایج حاصل از این تحقیق نشان داد که زیست‌لایه‌های موجود در شالیزارهای شمال ایران به مانند ریزوسفر گیاه برنج، میزبان طیف وسیعی از PGPRها از جمله انواع تثبیت‌کنندگان می‌باشند که با بهره‌گیری از آن‌ها، می‌توان راهکاری نوین در کشت محصولی سالم و پایدار ارائه داد. کودهای زیستی مبتنی بر پریفایتون به عنوان روشی جدید می‌توانند سلامت خاک و گیاه را تضمین کنند. | ||
| کلیدواژه‌ها | ||
| تثبیت زیستی نیتروژن؛ سیانوباکتری؛ کشاورزی پایدار؛ کود زیستی؛ نیتروژن | ||
| عنوان مقاله [English] | ||
| Feasibility of Isolating Heterotrophic and Autotrophic Diazotrophs from Periphyton Biofilm in Rice Fields and Evaluating Their Effects on Rice Growth under Greenhouse Conditions | ||
| نویسندگان [English] | ||
| Mehran Gholami1؛ Hosseinali Alikhani2؛ Hassan Etesami1؛ Zahra Karami1؛ Mohaddeseh Shirinzadeh1؛ Hamidreza Zare Guildehi1 | ||
| 1Department of soil science, University of Tehran | ||
| 2Soli Science and Engineering, College of Agriculture & Natural Resources, University of Tehran, Karaj-Iran | ||
| چکیده [English] | ||
| Background and Objectives: Rice, a key staple crop for over half the global population, is mainly grown in Asia and heavily depends on synthetic nitrogen fertilizers, which harm the environment and raise costs. Improving nitrogen use efficiency (NUE) in rice is essential, as current NUE is 28–35%, below the global average. Strategies to enhance NUE include balanced fertilization, slow-release fertilizers, nitrification inhibitors, precision nitrogen management, and breeding for efficient varieties. However, these approaches face challenges like high costs, labor intensity, and technological inaccessibility for small farmers. Biological nitrogen fixation (BNF) offers a promising alternative, using nitrogen-fixing bacteria to enhance NUE and yield while reducing chemical inputs. Studies show rice roots host beneficial bacteria like Azospirillum and Burkholderia, which support BNF. Yet, their effectiveness can be limited by soil and environmental factors. Periphytic biofilms, formed at the soil-water interface in rice paddies, are emerging as a valuable component in nitrogen cycling. Rich in microorganisms such as cyanobacteria and protozoa, these biofilms stabilize nitrogen in the ecosystem, reduce nitrogen losses, and act as natural biofertilizers. They support nitrogen fixation and nutrient uptake, boosting rice growth.Despite their benefits, periphytic biofilms are understudied. Recent research focuses on isolating nitrogen-fixing bacteria from these biofilms to assess their impact on nitrogen levels and rice growth. This study highlights the potential of diazotrophic biofilm enrichment as a sustainable solution to reduce fertilizer dependency, improve crop productivity, and promote environmental sustainability in rice farming. Materials and Methods: This study focused on evaluating soil, water, and periphytic biofilms in paddy fields in Guildeh, Iran, to investigate the impact of nitrogen-fixing microorganisms on rice plant nutrition. Soil, water, and periphyton samples were collected and analyzed for chemical properties using standard methods. Soil parameters such as pH, texture, nitrogen, phosphorus, and potassium content were measured. Microbial populations, including fungi and bacteria, were counted using plate count methods. To isolate nitrogen-fixing microbes (diazotrophs), periphyton samples were cultured on selective media. Bacterial and cyanobacterial isolates capable of growing on nitrogen-free media were identified through morphological and genetic analysis using 16S rRNA gene sequencing. Delftia lacustris (bacterial) and Nostoc sp. (cyanobacterial) were selected for further testing based on their nitrogen-fixing abilities. A greenhouse experiment was conducted in a completely randomized design with three replicates to assess the effects of these isolates, alone and in combination, on rice plant growth. Treatments included natural periphyton, periphyton enriched with isolates, and controls with and without nitrogen fertilizer. Rice seeds were planted in pots with paddy soil, and periphyton treatments were applied. Growth conditions were controlled, and plants were monitored for 40 days. At the end of the experiment, soil and plant samples were analyzed for nutrient content. Plant height, dry weight, nitrogen (by Kjeldahl method), phosphorus (by spectrophotometry), and potassium (by flame photometry) concentrations were measured. The study aimed to compare the effectiveness of microbial inoculants with chemical fertilizers in enhancing rice plant nutrition, supporting the use of diazotrophic organisms as sustainable alternatives in agriculture. Results: The study demonstrated that applying periphytic biofilms, enriched with beneficial microorganisms, significantly improved soil fertility by enhancing the availability of nitrogen, phosphorus, and potassium in paddy fields. The enriched periphyton treatment (P+B+C) increased total soil nitrogen by 37.8% and ammonium by 42.1% compared to the unfertilized control. This improvement is largely due to biological nitrogen fixation carried out by microorganisms such as Nostoc species and Delftia lacustris, which convert atmospheric nitrogen into forms accessible to plants. Ammonium content also rose across all periphyton treatments after the growth period, indicating the active role of these microbial communities in nitrogen cycling. Soil phosphorus levels increased significantly with periphyton treatments (35%). The biofilms enhanced phosphorus availability by harboring phosphate-solubilizing microorganisms that release enzymes such as phosphatases. These enzymes break down organic phosphorus into forms that plants can absorb. Additionally, the periphyton helped regulate phosphorus availability over time, ensuring a steady supply during different growth stages of rice plants. Potassium availability also improved due to the presence of potassium-solubilizing microorganisms within the periphyton (15.36%). These microbes released substances that aided in converting fixed potassium into soluble forms, which plants can uptake. Periphyton also served as a reservoir, storing potassium early in the plant’s development and releasing it when needed later in the growth cycle. Rice plants treated with periphyton showed clear improvements in growth, including greater height, biomass, and higher nutrient content. These benefits were linked to the activity of plant growth-promoting microbes that produce hormones, facilitate nutrient absorption, and protect against stress. Notably, Delftia lacustris and Nostoc species were crucial contributors to these effects. Overall, periphyton-based treatments offer a sustainable and effective alternative to chemical fertilizers, enhancing nutrient cycling and supporting healthier, more productive rice cultivation systems. Conclusion: The results show that applying periphyton can significantly improve soil fertility and enhance the nutritional status of rice plants. Periphyton, rich in plant growth-promoting rhizobacteria (PGPR), plays a key role in supporting rice growth. Treatments involving periphyton produced better outcomes than other treatments, especially when enriched with Delftia lacustris and Nostoc species, which greatly increased nitrogen availability compared to natural periphyton and controls. While nitrogen improvement was the main focus, phosphorus and potassium levels in the soil also showed notable increases. These nutrient enhancements supported greater rice plant height and dry weight, highlighting the value of periphyton enrichment in improving soil quality and plant development. The study emphasizes the potential of using microbial communities like periphytic biofilms to promote sustainability in rice production systems. Future research should explore the long-term effects of periphyton application across different environmental conditions to optimize its use in sustainable agriculture worldwide. Understanding the role of these biofilms in nitrogen cycling can inform biofertilization strategies aimed at reducing synthetic fertilizer use and increasing agricultural productivity. Overall, the findings suggest that periphytic biofilms act as important reservoirs for nitrogen-fixing microbes, playing a vital role in nutrient cycling in both aquatic and terrestrial ecosystems. | ||
| کلیدواژه‌ها [English] | ||
| Biofertilizer, Biological nitrogen fixation, Cyanobacteria, Nitrogen, Sustainable agriculture | ||
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