نوع مقاله : مقاله پژوهشی

نویسندگان

• بنفشه رضایی نیکو ¹
• نعیمه عنایتی ضمیر ²
• مجتبی نوروزی مصیر ³

¹ دانشجوی سابق کارشناسی ارشد گروه خاکشناسی، دانشکده کشاورزی، دانشگاه شهید چمران اهواز، اهواز، ایران

² دانشیارگروه خاکشناسی، دانشکده کشاورزی، دانشگاه شهید چمران اهواز، اهواز، ایران

³ استادیار گروه خاکشناسی، دانشکده کشاورزی، دانشگاه شهید چمران اهواز، اهواز، ایران

چکیده

برای جداسازی باکتریهای انحلال کننده روی از منبع اکسید روی نمونه خاک از ریزوسفر ذرت تهیه و با استفاده از محیط کشت جامد و مایع دارای روی از منبع اکسید روی غربال‌گری شدند. 50 جدایه باکتری از ریزوسفر ذرت جداسازی شدند. که از بین این جدایه‌ها 16 جدایه که دارای شاخص حلالیت روی یک و بالاتر بودند بر اساس خصوصیات مرفولوژیکی، بیوشیمیایی و فیزیولوژیکی برای مطالعات بیشتر انتخاب شدند. جدایه‌ای که دارای توانایی بیشتری در انحلال روی، فسفر، پتاسیم و تولید اکسین بود انتخاب و شناسایی شد. این stenotrophomonas maltophilia بودند. تاثیر جدایه Z14 بر رشد گیاه ذرت بررسی شد. این پژوهش در زیستگاه درون شیشه‌ای با آرایش فاکتوریل در قالب طرح کاملاً تصادفی در پنج تکرار انجام شد. فاکتورهای آزمایش شامل دو سطح باکتری B1 (شاهد)،B2 (stenotrophomonas maltophilia) و سه سطح کود سولفات روی Zn0 (بدون افزودن کود روی)، Zn20 (50 درصد نیاز گیاه) و Zn40 (100 درصد نیاز گیاه) بودند. بعد از یک دوره 20 روزه شاخص کلروفیل اندازه‌گیری و بخش هوایی و ریشه گیاه برداشت شد. صفات وزن تر و خشک اندام هوایی و ریشه، طول ریشه و بلندی گیاه اندازه‌گیری شد. این بررسی نشان داد پیامد مایه‌زنی باکتری بر همه ویژگی‌های اندازه‌گیری شده در سطح یک درصد معنی‌دار است. تمام ویژگی‌های ذکر شده در حضور باکتری بالاترین اندازه‌ها را داشتند. با توجه به مشکل کمبود روی قابل جذب در خاک‌های آهکی خوزستان و با توجه به توانایی آن در انحلال روی، فسفر، پتاسیم و تولید اکسین(خصوصیات محرک رشدی) می‌تواند به عنوان کود زیستی به کاربرده شوند.

کلیدواژه‌ها

• کود
• پتاسیم
• روی
• فسفر
• رشد

موضوعات

• تغذیه گیاه، حاصلخیزی خاک و کودها

عنوان مقاله [English]

Effect of zinc solubilizing growth promoter bacterium on plant growth under laboratory conditions

نویسندگان [English]

• banafsheh rezaee niko ¹
• Naeimeh Enayatizamir ²
• mojtaba norozi masir ³

¹ M.Sc. graduate student of Soil Science, Department of Soil Science, Shahid Chamran University of Ahvaz

² Associate Prof., Department of Soil Science, Shahid Chamran University of Ahvaz,

³ Assistant Prof., Department of Soil Science, Shahid Chamran University of Ahvaz

چکیده [English]

Introduction

Zinc is one of the imperative micronutrients required relatively in small concentrations in tissues for healthy growth and reproduction of plants. Zinc deficiency in plants leads to reduced membrane integrity and synthesis of carbohydrates, auxins, nucleotides, cytochromes, and chlorophyll and develops susceptibility to heat stress. The solubility of Zn is highly dependent upon soil pH and moisture and hence arid and semiarid areas are often zinc-deficient. The use of microorganisms with the aim of improving nutrients availability for plants is an important practice and necessary for agriculture. Zinc-solubilizing microorganisms can solubilize zinc from inorganic and organic pools of total soil zinc and can be utilized to increase zinc availability to plants. Therefore, the present study was carried out to isolate and characterize native zinc-solubilizing bacteria from Zea mays rhizosphere and evaluate their zinc-solubilizing potential and the effect of zinc solubilizing isolate on Zea mays growth.

Materials and Methods:

In vitro zinc solubilization assay of isolates was done using 0.1% zinc from zinc oxide in both plate and broth assays. Actively growing cultures of each isolates were spot-inoculated (7 µL) onto the agar and plates were incubated at 28°C for 48 h. The clearing zone around colony was recorded. Quantitative study of zinc solubilization was studied in 150 mL conical flasks containing 50 mL of liquid mineral salt medium. The broth was inoculated with 10 µL of overnight grown bacterial inoculum and incubated for 72 h at 160 rpm in an incubator shaker at 28°C. After incubation, the culture broth was centrifuged and the concentration of Zn in the supernatant was estimated in atomic absorption spectrophotometer. Among these isolates, 18 isolates with a solubility index of 1 and higher were selected based on morphological, biochemical and physiological characteristics for further studies. An isolate with more ability to dissolve zinc, phosphorus, potassium and auxin production were selected for investigation the effect of isolate on Zea mays growth. Maize seeds of cultivable variety were surface sterilized with 1% sodium hypochlorite for 5 min and washed several times with sterile distilled water. Seeds were treated with inoculum containing 108 cfu•g−1 of isolate. A factorial experiment in a completely randomized design with five replications was conducted. The treatments included two levels of bacteria B1 (control), B2 (Stenotrophomonas) and zinc sulfate fertilizer at three levels of Zn0 (control), Zn20 (20 kg/ha) and Zn40 (40 kg/ha). After 60 days of sowing, plants were removed from the tubes carefully and biometric parameters like root length, shoot length and dry mass of plants were recorded as the indicative of plant growth.

Results and Discussion:
A total of 50 bacterial isolates were isolated from corn rhizosphere. Of all, sixteen isolates showed solubilization halo on plate agar medium. Among the cultures, Z1, Z3, Z16 and Z12 showed the highest solubilisation zone in ZnO amended medium with maximum solubility index (1.3). Quantitative assay for zinc solubilisation revealed that Z14 were able to dissolve 44.8 ppm from ZnO in liquid medium. While solubility index of this isolate was lower that above mentioned isolates (1). Of all, the isolate Z14 with highest zinc solubilisation by broth assay was characterized and identified as Stenotrophomonas
species based on Gram-negtive reaction and other biochemical and physiological properties. This isolate was able to produce auxin and dissolve insoluble phosphorus and potassium from the source tricalcium phosphate and vermiculte, respectively. One of these strains (Z14), Stenotrophomonas was used as inoculum in corn culture.
Seed bacterization of maize with zinc solubilising Stenotrophomonas enhanced the plant growth significantly after 15 days. Results indicated a significant interaction effect of bacterium and fertilizer on shoot dry weight and chlorophyll content (p < 0.01). The maximum spad index and wet weight of aerial part obtained at present of bacterium and without using of zinc sulfate. The main effect of bacterium on wet and dry weight of root and wet weight of aerial part, root length and shoot height was significant (p < 0.01). َApplication of bacterium in all treatments caused to increased all measured parameters in th eperesence of zinc fertilizer or absence of zinc fertilizer.
Conclusion: PGPR is known as a group of useful rhizospheric bacteria that increase plant growth. Today, the increasing use of PGPRs in agriculture as an alternative to chemical fertilizers to prevent environmental contamination.

کلیدواژه‌ها [English]

• Fertilizer
• Potassium
• Zinc
• phosphorus
• Growth