اثر مایه‌زنی با قارچ claroideoglomus etunicatum بر گیاه‌پالایی نیکل و جذب برخی عناصر ریزمغذی توسط گیاه ذرت (zea mays l.)

استفاده از قارچ‌های میکوریزا آربوسکولار به دلیل نقش آن‌ها در توانمندسازی گیاهان برای مقاومت در برابر سمیت نیکل اهمیت دارد. در این مطالعه اثر مایه‌زنی گیاه ذرت با قارچ‌ claroideoglomus etunicatum بر ویژگی‌های رشدی، غلظت فسفر، نیکل و برخی عناصر ریزمغذی و محتوای گلومالین خاک واکنش‌پذیر بردفورد (brsg) در سطوح مختلف نیکل خاک ارزیابی شد. آزمایش به صورت فاکتوریل در قالب طرح کاملاً تصادفی اجرا شد. عامل اول شامل سطوح مختلف کاربرد نیکل (شاهد، 50، 100، 250 میلی‌گرم نیکل بر کیلوگرم خاک) و عامل دوم شامل سطوح کاربرد قارچ میکوریزا آربوسکولار (شاهد بدون مایه‌زنی و مایه‌زنی شده با c. etunicatum) بود. گیاهان مایه‌زنی شده ارتفاع بوته و وزن خشک بخش هوایی بیشتری را نسبت به گیاهان بدون مایه‌زنی نشان دادند. brsg ساده قابل استخراج (ee brsg) در تمام سطوح نیکل بطور معنی‌داری در گیاهان مایه‌زنی شده بیشتر از بدون مایه‌زنی بود. در تیمار ni100، brsg کل (t brsg) به‌میزان 8/15 درصد نسبت به سطح شاهد نیکل افزایش نشان داد. همچنین اثر مایه‌زنی میکوریزی بر غلظت فسفر، روی و مس بخش هوایی افزایشی و معنی‌دار بود. غلظت نیکل در بخش هوایی گیاهان مایه‌زنی شده در تیمارهای ni100 و ni250 به‌ترتیب به‌میزان 30 و 33 درصدکمتر از گیاهان بدون مایه‌زنی بود. فاکتور انتقال در گیاهان مایه‌زنی شده در همه سطوح به‌جز سطح ni50 بطور معنی‌داری کمتر از گیاهان بدون مایه‌زنی بود. این مطالعه پتانسیل همزیستی میکوریزاآربوسکولار را در راستای فناوری تثبیت گیاهی نشان می‌دهد و بهره برداری از این قارچ‌ها می‌تواند در تثبیت گیاهی نیکل در خاک‏هایی با آلودگی زیاد و در سطح وسیع موثر باشد.

effect of claroideoglomus etunicatum inoculation on nickel phytoremediation and uptake of some micronutrients by maize (zea mays l.)

introduction nickel (ni) is a fundamental micronutrient in plants but hampers plant growth and metabolism at elevated levels in the soil. ni toxicity to plants is manifested mainly by the decrease in germination efficiency, the inhibition of growth and root branching, damage to the photosynthetic apparatus, and the induction of oxidative stress. in recent years, the use of arbuscular mycorrhiza (am) has gained importance for its role in enabling plants to tolerate ni toxicity. however, information about their effectiveness in alleviating ni stress is scanty. the process of element transport in plants may be assumed to be different among heavy metal concentrations in the substrate. consequently, whether am fungi enhance the metal transport to shoots (phytoextraction) or immobilize them in the roots (phytostabilization) mainly depends on metal concentration in the substrate. moreover, ni has been reported to compete with other micronutrients for absorption sites, which would trigger different changes of elements concentrations. the aim of this study was to investigate the role of am fungus in alleviating ni stress and its possible function in plant nutrition.materials and methods in this study, the effects of mycorrhizal inoculation of corn plants with claroideoglomus etunicatum on alleviation of ni impact on plant were evaluated. some growth characteristics of the plant, phosphorus content, micronutrients (iron, zinc, and copper), concentration of nickel in shoot and root, and bradford reactive soil glomalin (brsg) were assessed. accordingly, a two factor experiment (am inoculation × ni levels) in completely randomized design was done. the factors included the different concentrations of nickel (control (ni0), 50 (ni50), 100 (ni100) and 250 (ni250) mg kg 1), and the levels of fungal application (control without inoculation (nm) and inoculated with c. etunicatum (am)). plants were grown in the greenhouse for 90 days and then the growth parameters were recorded. the concentration of phosphorus was measured spectrophotometrically and the concentration of iron, zinc, copper, and nickel in digested plant samples was determined by icp oes. bio concentration factor and translocation factor were also calculated. the colorimetric method was used to quantify bradford reactive soil glomalin. the bradford protein assay was utilized to determine the concentration of easily extractable and total bradford reactive soil glomalin using bovine serum albumin (bsa) as a standard.results and discussion increasing the nickel concentration in soil decreased the dry weight of root and shoot, and this decrease was significant in both inoculated and non inoculated plants at ni250 treatment (p≤0.05). plants inoculated with am fungus showed significantly higher height and dry weight of shoots than plants without inoculation (p≤0.05), but the effect of mycorrhizal inoculation on the dry weight of roots was not statistically significant. the effect of nickel on the colonization percentage of roots and easily extractable bradford reactive soil glomalin (ee brsg) was significant. ee brsg was higher at all levels of nickel in inoculated plants than in non inoculated ones. moreover, with the increase of nickel concentration in soil up to 100 mg kg 1, total bradford reactive soil glomalin (t brsg) increased. the concentration of phosphorus in the shoots and roots of inoculated plants was higher than in non inoculated plants. mycorrhizal inoculation significantly increased the concentration of zinc and copper in the aerial part. moreover, nickel treatment did not show a statistically significant effect on the concentration of copper in the aerial part and iron in the roots. inoculation with am fungus showed a significant impact on the nickel concentration of the shoots and roots, and the concentration of nickel in the roots of inoculated plants at ni250 level was significantly higher than plants without inoculation by 29% (p<0.05). mycorrhizal plants had lower nickel concentrations in the aerial part at ni100 and ni250 by 30% and 33% respectively, compared to the nm plants. the translocation factors in inoculated plants at ni100 and ni250 levels were significantly lower than that in non inoculated plants, which indicates the role of fungi in preventing the transfer of nickel to the aerial parts and its accumulation in the roots. moreover, inoculated plants in the ni100 and ni250 treatments showed a significantly lower bio concentration factor by 36% and 22%, respectively, compared to non inoculated plants.conclusion the results showed that am colonization can help to reduce the toxicity of nickel by increasing plant growth and uptake of phosphorus, zinc and copper. am colonization had a prominent impact in preventing the nickel transfer to the aerial parts and its accumulation in the roots. it seems that am fungi can be used for phytostabilization of heavy metals in soils.