نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه زیستشناسی، دانشگاه پیام نور، تهران- ایران
2 گروه آموزشی زیست شناسی، دانشگاه فرهنگیان، صندوق پستی 889-14665،تهران- ایران
3 دانش آموخته ،گروه زیستشناسی، دانشکده علوم و فناوریهای زیستی، دانشگاه اصفهان، اصفهان
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Nickel (Ni) and zinc (Zn) are essential micronutrients and most of their contaminations are related to the increasing use of fertilizers and pesticides. The present study focuses on the effects of the different concentrations of Ni (0, 17, 43, 85 and 170 mM) and Zn (0, 60, 120, 300 and 600 mM) on the growth factors, Ni and Zn accumulation, and the concentration of Iron (Fe) in roots and shoots. Th experiments carried out in this study used a randomized complete block design with three replications in the growth chamber at Isfahan University. The basil plants the seeds of which were provided from Pakan Bazr Company (Isfahan) were transferred to hydroponic mediums and after proper vegetative growth, they were exposed to different concentrations of Ni and Zn for 10 days. The findings showed that the increasing concentrations of Ni and Zn resulted in a significant decrease in the growth, so that the shoots and roots dry weight decreased at the highest level of treatments in Ni (170 mM) in comparison with the control treatment by 52.8% and 65.9% and Zn (600 mM) by 38.9% and 41.7%, respectively. With the increasing concentration of Ni and Zn in the medium, the accumulation of both heavy metals in the roots and shoots increased which caused a disruption in Fe transport, hence an enhancement the in the accumulation of Fe in the roots, and decline its accumulation in shoots. Fe accumulation in root at highest level of Ni and Zn stress (170 and 600 mM) increased in comparison with the control treatment by 51% and 89.9%%, respectively, while it reduced in shoot at highest level of Ni and Zn stress by 66.8% and 59%, respectively. However, translocation factor of Zn (mean translocation factor in treatments; 0.56) was higher than Ni (mean translocation factor in treatments; 0.28) which indicated that basil is resistant to Zn accumulation. These results revealed that basil is an Ni and Zn excluder plant, so root growth was restricted in comparison with shoot growth. Therefore, the excessive use of micronutrient fertilizers has not only contaminated agricultural soils, but also entered into food chains.
کلیدواژهها [English]
EXTENDED ABSTRACT
Nickel (Ni) and zinc (Zn) are essential micronutrients and most of their contaminations are related to the increasing use of fertilizers and pesticides. Basil (Ocimum basilicum L.) is a medicinal plant that is also used as a vegetable. By the increase in the Earth's population and consequently the rising demand for agricultural products, along with the limitation of farm lands, the use of chemical fertilizers to enhance their productivity has become common, Therefore, the contamination of agricultural soils has increased due to heavy metals. The present study focuses on the effects of the different concentrations of Ni (0, 17, 43, 85 and 170 mM) and Zn (0, 60, 120, 300 and 600 mM) on the growth factors, Ni and Zn accumulation, and the concentration of Iron (Fe) in roots and shoots.
In this study, basil (Ocimum basilicum) seeds were obtained from Pakaan Bazr Company. The disinfected seeds were transferred to perlite pots for germination, watered with distilled water, and fed with a modified Hoagland solution at the two-leaf stage. After 12 days, four uniform seedlings were transferred to plastic pots containing half-strength Hoagland medium and grown in a greenhouse with day/night temperature of 25/20 °C, a 16 h photoperiod. After 25 days plants were transferred to hydroponic mediums and after proper vegetative growth, they were exposed to 0, 17, 43, 85, 170 mM treatments of nickel (NiSO4.6 H2O) and 0, 60, 120, 300, 600 mM treatments of zinc (ZnSO4.7 H2O) for 10 days. The nutrient solutions were aerated continuously and changed every three days. Shoot and root dry weights were measured after drying in an oven at 70 °C for 48 h and Ni, Zn and Fe concentrations were determined in root and shoots using a flame atomic absorption spectrophotometer (AAS, Shimadzu model 6200). The Ni, Zn, Fe translocation factor (TF) from root to shoot were calculated as their concentration in the shoot divided by their concentration in the root. The experiments carried out in this study used a randomized complete block design with three replications. Duncan’s test with P < 0.05 as significance threshold was used to compare individual means.
The results showed that with the increasing concentrations of Ni and Zn in the medium, the growth significantly decreased, so that the shoots and roots dry weight decreased at the highest level of treatments in Ni (170 mM) in comparison with the control treatment by 52.8% and 65.9% and Zn (600 mM) by 38.9% and 41.7%, respectively. The ratio of shoots to roots increased at the high levels of Ni treatment (85, 170 mM), but this increase only occurred at the highest level of Zn (600 mM). With increasing in the concentrations of heavy metals in the medium, their accumulation in the roots and shoots increased, but the accumulation in the roots was always more than in the shoots in both heavy metals. The translocation factor of these heavy metals to shoots varied, but the translocation factor of Zn was consistently greater than Ni which indicated basil is resistant to Zn accumulation. With the enhancing concentration of Ni and Zn in the medium, the accumulation of both heavy metals in the roots and shoots increased which caused a disruption in Fe transport, hence an enhancement the in the accumulation of Fe in the roots, and decline its accumulation in shoots. Under the highest levels of Ni and Zn stress (170 and 600 mM), Fe accumulation in the roots increased by 51% and 89.9%, respectively, compared to the control treatment. In contrast, Fe levels in the shoots decreased by 66.8% for Ni and by 59% for Zn under the same stress conditions. Additionally, the translocation factor for Zn (mean: 0.56) was greater than Ni (mean: 0.28).
Considering the higher accumulation of heavy metals Ni and Zn in the roots of the basil plants, they can be classified as excluder plants for these elements, so root growth was restricted in comparison with shoot growth. Although the basil displayed greater resistance to zinc. With increasing in the concentrations of essential heavy metals (Ni and Zn) in the medium, Fe accumulation in the roots also increased, while its transfer to the shoots decreased. This reduction in translocation of Fe is one of the reasons for the reduced growth in the shoots due to the deficiency of essential elements. Therefore, the excessive use of micronutrient fertilizers has not only contaminated agricultural soils, but also entered into food chains.
Behrooz Salehi-Eskandari: Writing – review & editing, Software, Methodology. Zahra Ghasemi: Writing – review & editing. Somayeh Mousavi Rizi: writing – original draft, Investigation.
Data will be made available on request.
The authors are thankful to the Graduate School of University of Isfahan for providing the research facilities needed for this study.
The authors avoided data fabrication, falsification, plagiarism, and misconduct.
The author declares no conflict of interest.
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