S. Keshavarz; R. Ghasemi
Abstract
Introduction: Chromium (Cr) is one of the toxic metals widely used in leather tanning, alloy preparation, electroplating, drilling mud, refractory steel and catalytic manufacture. Besides the toxicity of chromium to human, it also disturbs the soil ecology and plant growth due to its toxic nature even ...
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Introduction: Chromium (Cr) is one of the toxic metals widely used in leather tanning, alloy preparation, electroplating, drilling mud, refractory steel and catalytic manufacture. Besides the toxicity of chromium to human, it also disturbs the soil ecology and plant growth due to its toxic nature even at low concentration. Phytoremediation is effective and can be viewed as a relatively low cost, solar energy driven process for the management of contaminated soils. Hiwever the heavy metal toxicity adversely affects the plant growth and development. We can use some chemical compounds to increase plant resistance to heavy metal and increase the efficiency of phytoremediation. These days, foliar application of plant growth regulators such as Gibberelic acid Indole acetic acid and Benzyl amino purine are considered for various purposes such as enhancing plant growth and resistance to salinity, drought and heavy metals. Exogenous application of phytohormones can modulate the toxicity of Cr on plants most probably by maintaining hormonal balance of plant under metal stress. surfactants effectively enhance metal ion transfer to aqueous and hence increase their availability. Assessing surfactant assisted phytoremediation is important in order to ascertain the extent of its effectiveness under different conditions and to find its optimum level for metal phytoremediation. The application of plant growth regulators and surfactants can be an effective way to cope with stresses such as heavy metal contamination. The objectives of this study were to determine the effects of the growth hormones Gibberelic acid, Benzyl amino purine and Indole acetic acid alone and combined with surfactant on plant growth, concentration and uptake of Cr, Fe, Mn, Cu and Zn and some phytoremediation factor for Cr.
Material and Methods: The soil was air-dried and grounded to pass through a 2-mm sieve then was analyzed to determine various soil physic-chemical properties using standard methods. A greenhouse experiment was conducted in a completely randomized design with a factorial arrangement of 3 × 4 including three levels of surfactant (control, 2.5 and 5 mmol kg-1 soil) and four levels of plant growth regulators (control, Gibberellic acid, Indole acetic acid and Benzyl amino purine). All soils were contaminated by 5 mg/kg chromium and incubated for 1 month. During incubation, the soil samples were maintained at field capacity by distilled water. Safflower (Cartamus tinctorius L.) seeds were disinfested with 10% sodium hypochlorite, washed three time with distilled water and planted in the pots. Growth regulators were sprayed at three stage of 30, 20 and 40 days after planting at concentration of 1 mM. The plants were kept in the standard condition of greenhouse and the soil moisture content was maintained at field capacity by distilled water. Sixty days after planting, the plants were harvested and washed with distilled water, and then dried in oven at 65 Celsius until they reached a constant weight. Afterwards, the over-dried plant samples were grounded. Then dry ashing and extracting with 2 normal hydrochloric acid, the concentration of Cr, Fe, Zn, Cu and Mn in shoot was determined by atomic absorption (Shimadzu AA-670). The analysis of variance (ANOVA) was performed using a completely randomized design. Significantly different treatment means were separated using Duncan test (P < 0.05). Biological accumulation coefficient (BAC) and uptake index (UI) were calculated with a specific formula.
Results and Discussion: The results showed that addition of surfactant and growth regulators caused a significant increase in shoot dry weight, biological accumulation coefficient, uptake index and chromium concentration and uptake. Addition of surfactant reduced the concentration and uptake of iron in the absence of growth regulators, but in the presence of plant growth regulators, application of tween 80 increased iron concentrations. Application of 5 mmol kg-1of surfactant decreased mean concentration of manganese, copper and zinc. While addition of 2.5 mmol kg-1 of surfactant increased metals concentrations. Although addition of 5 mmol kg-1 surfactant increased dry weight, it did not have a satisfied effect on increasing the concentration of the elements in the plant. Plant growth regulators increased uptake of elements which is a protective mechanism against stresses.
Conclusion: It appears that using plant growth regulators increased the resistance of the plant to chromium toxicity probably through increasing absorption of the elements such as Fe, Mn, Cu and Zn. According to the results, application of tween 80 along with plant growth regulators could increase safflower capability to cope with chromium toxicity.
N. Abdar; R. Ghasemi
Abstract
Introduction: Zinc (Zn) is an important nutrient element for plants growth, which plays an important role in the metabolism of plant. Zn uptake by plants requires release of Zn adsorbed onto the soil constituents and even Zn containing minerals. The release of Zn from soil surface to the soil solution ...
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Introduction: Zinc (Zn) is an important nutrient element for plants growth, which plays an important role in the metabolism of plant. Zn uptake by plants requires release of Zn adsorbed onto the soil constituents and even Zn containing minerals. The release of Zn from soil surface to the soil solution is an important factor that controls availability of Zn for growing plants. Kinetics of Zn release from soil could indicate ability of soil to Zn supply to plants. The purpose of present study was to investigate the effects of soil depth and canopy of three cultivars of palm including Shahani, Ghasab and Halavani on release kinetics of native Zn by AB-DTPA extractant.
Materials and Methods: In order to investigate the effects of depth and vegetation on the pattern of Zn release, 54 soil samples were collected from inside and outside canopy of different palm cultivars (Shahani, Halavani and Ghasab), three depths (0-20, 20-40 and 40-60 cm) with three replications. These samples were collected from village of Simakan, located in the city of Jahrom. Extraction was performed after eight shaking times (5, 15, 30, 60, 120, 240, 480, and 1440 min) with ammonium bicarbonate-diethylene triamine penta acetic acid (AB-DTPA). After each shaking time, samples were immediately centrifuged for 15 min, and then filtered through filter paper. The concentration of Zn in solutions were determined using an atomic absorption spectrophotometer (AA-67OG). Seven commonly used kinetics models in nutrient release studies were used to describe Zn release including zero-order, first-order, pseudo-first-order, pseudo-second-order, power function, parabolic diffusion, and simple elovich. Data analysis and drawing of charts were done by SAS software and Excel program, respectively. Relatively high value of coefficient of determination and low value of standard error of estimate were considered as criteria for the best fit.
Results and Discussion: The results of this study showed that the simplified Elovich, parabolic diffusion and power function equations well described the pattern of Zn release from soil as evidenced by higher coefficient of determination and lower values of the standard error of the estimate. The Zn release pattern in all soil samples consisted of a quick stage from the start of the experiment to 240 minutes and a slower stage at subsequent times. The correlation between the coefficients of the kinetic equations of the power function, simplified Elovich and parabolic diffusion showed that there was higher correlations between the coefficients of the equations obtained from the under canopy in comparison with those of out of canopy. Although soil is a major factor influencing vegetation growth and characteristics, plants could, in turn, also affect different soil properties. In addition, the palm root system and the rhizosphere exhibit a complex diversity, which could regulate the plant homeostasis. The interaction of root-microorganism in the rhizosphere can cause many of the physical, chemical and biological properties of the rhizosphere soil that are different from the bulk soil. Important changes in the soil properties of the rhizosphere environment include soil pH, soil oxidation-reduction reactions, soil moisture, and nutrient availability for microorganisms and plant. Root exudates also contribute to enhance of the availability of elements by reducing the pH of the rhizosphere and creating bioavailable Zn complex. Recent studies have shown that root exudates can act as an influential factor in extracting significant values of plant nutrients from calcareous soils. Our results showed that the amount of accumulated Zn released from the under canopy soils was more than the out of canopy soils, and the highest amount of accumulated Zn was released in the soils under canopy of Ghasab cultivar.
Conclusion: Results of present study showed that the values of Zn released from the under canopy soils was higher than interspaces soils, and the highest amount of accumulated Zn was released in the soils under canopy of Ghasab cultivar. Such observations clearly indicate that palm trees are able to supply Zn absorption capacity under their own canopy soils. Therefore, it appears that higher rates of Zn release from the under canopy soils in comparison with interspaces could be attributed to higher root exudates which impact soil properties, microorganism activities and lower pH which, in turn, increase the amounts of metals including of Zn release and bioavailability. Further researches on the effect of palm root system on physical and chemical properties of soil, including organic matter, soil pH, which could cause great impacts on the amount of Zn release are highly recommended.
Mahshid Shafigh; reza ghasemi; abdolmajid ronaghi
Abstract
Introduction: Plants can uptake, bioaccumulate and immobilize different metals in their tissues. Phytoremediation technique has been used to remove hazardous substances including heavy metals from the environment. Assisted phytoremediation is usually the process of applying a chemical additive to heavy ...
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Introduction: Plants can uptake, bioaccumulate and immobilize different metals in their tissues. Phytoremediation technique has been used to remove hazardous substances including heavy metals from the environment. Assisted phytoremediation is usually the process of applying a chemical additive to heavy metal contaminated soils to enhance the metal uptake by plants. The main objective of present study was to investigate the effectiveness of plant growth regulators (PGRs) and a humic substance (HS) on Ni phytoremediation by maize in a Ni-pollutrd calcareous soil.
Materials and Methods: The experiment designed as a 5×3 factorial trial arranged in a completely randomized design with three replicates. Three kilograms of soil was placed in plastic pots and pots were watered with distilled water to field capacity and maintained at this moisture level throughout the experiment by watering the pots to a constant weight. The soils were polluted with 250 mg Ni Kg-1 as Ni-nitrate Ni (NO3)2. Six maize (Zea mays L.) seeds were planted 2 cm deep in soil and thinned to three uniform stands 1 week after emergence. Treatments consisted of three levels of soil application of commercially humic substance, HS, (0, 3, and 6 mg kg as Humax 95-WSG containing about 80% humic acid, and about 15% fulvic acid) and five levels of PGRs (0 or 10 µM GA3, IAA, BAP and SA). The HS was applied as split doses in three times at 15 day intervals along with irrigation water. The seedlings were exposed to aqueous solutions of HS 16 days after sowing for the first time. Prepared solutions of PGRs were sprayed three times at 15 day intervals from emergence. Seven weeks after planting, shoots were harvested and roots were separated from soil carefully, both parts were rinsed with distilled water and dried at 65°C for 72 h, weighed, ground, and dry meshed at 550°C. Root and shoot dry matter and Ni concentration and uptake and phytoremediation criteria were considered as plant responses. Data were statistically analyzed using SAS and SPSS software packages. Application of different PGRs had no considerable effect on phytoextraction or translocation efficiencies. Among the four PGRs studied application of SA and BA significantly increased mean uptake efficiency.
Results and Discussion: Among four PGRs evaluated, application of GA3 increased mean shoot dry matter yield and application of SA increased mean root dry matter yield. Application of the highest HS level (6 mg kg-1) decreased both mean root and shoot dry weight. Application of SA increased Ni concentration in both maize root and shoot. Application of BA only increased Ni concentration in maize root. Although application of the highest HS level (6 mg kg-1) caused an increase in Ni concentration in maize shoot, this effect was attributed to the influence of HS on the decrease in decreasing dry weight of maize shoot. Application of all PGRs except GA3 increased leaf greenness criterion. Addition of HS had no significant effect on leaf greenness. Application of PGRs enhanced root concentration factor (RCF) and decreased translocation factor (TF). Among PGRs evaluated, BA was the most effective on TF, and SA or BA was the most effective on RCF. However HS were not significantly influenced these phytoremediation criteria, as compared with control. The efficiency of PGRs in root Ni uptake was in the order of SA > BA > GA3 > IAA. Application of BA had a significant effect on Ni distribution among root and shoot, in comparison with other PGRs, and caused an increase and a decrease in root and shoot uptake of Ni, respectively. However HS had a negative effect on tolerance index and its application decreased root and shoot dry weights. Results showed that the values of Ni in maize root was considerably higher than that of maize shoot demonstrated that phytostabilization was the main mechanism involved in the phytoremediation of Ni by maize and application of PGRs was effective on this mechanism.
Conclusion: Results reported here indicated that although the addition of HS did not cause a significant effect on Ni phytoremediation, application of most studied PGRs had a positive effect on Ni phytoremediation by maize. Application of SA and BA increased uptake efficiency and RCF and application of GA3 increased shoot dry matter and tolerance index. The fact that Ni uptake by roots was significantly higher than that of shoots demonstrated that phytostabilization was the main mechanism involved in the phytoremediation of Ni by maize. According to results reported herein the addition of PGRs especially SA is likely to be promising in phytostabilization of Ni in calcareous soils polluted with this metal.
leila zare; abdolmajid ronaghi; Seyed Ali Akbar Moosavi; Reza Ghasemi
Abstract
Introduction: Vermicompost is one of the important bio-fertilizer which is the product of the process of composting different organic wastes such as manures and crop residues using different earthworms. Vermicomposts, especially those are derived from animal wastes,contain the large amounts of nutrients ...
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Introduction: Vermicompost is one of the important bio-fertilizer which is the product of the process of composting different organic wastes such as manures and crop residues using different earthworms. Vermicomposts, especially those are derived from animal wastes,contain the large amounts of nutrients compaired with the composts prepared from crop residues. Vermicomposts contain plant available form of nutrients such as nitrate nitrogen, exchangeable phosphorus and potassium, calcium and magnesium. Nowadays, the use of vermicompost in sustainable agriculture to improve the growth and quality of fruits and crops is very common. Drought occurs when the amount of moisture in soil and water resources and rainfall is less than what plants need for normal growth and function. Two thirds of farm lands in Iran have been located in arid and semi-arid regions with annual rainfall less than150 mm that has been distributed irregularly and unpredictable during growth season imposing water stress in most crops. It indicates the importance of water management and proposing different strategies for mitigating detrimental effect of water stress in croplands. Due to the fact that crops nutrient management under drought and water stress using organic fertilizers is an effective method in reaching to high yields in sustainable agriculture, the objective of the present study was to investigate the influence of vermicompost application on reducing the adverse effects of water stress on the growth and chemical composition of corn in a calcareous soil.
Materials and Methods: In order to study the influence of water stress and application of vermicompost on corn dry matter yield and nutrients concentration of corn shoot, a greenhouse factorial experiment (4×3) in completely randomized design with three replications was conducted in college of agriculture, Shiraz university, Shiraz, Iran. The factors consisted of four vermicompost levels (0, 10, 20 and30g kg-1soil equal to 0, 20, 40 and 60 Mg ha-1) and three moisture levels(100, 80and 60%of field capacity(FC)). The soil samples were collected (0-30 cm depth) from a calcareous soil (Fine, mixed, mesic, Typic, Calcixrepts), located at Bajgah, Shiraz, Iran. Soil samples were mixed thoroughly with different levels of vermicompost and transfred to plastic pots. Six corn seeds were planted in each pot and were thinned to three uniform plants, one week after germination. Eight weeks after germination, corn shoots were harvested, dried and recorded. Plant samples were grind using a portable grinder and transferred to the laboratory for chemical analysis. The collected data were statistically analysed using SAS software (9.1.3) package.
Results and Discussion: The results indicated that with increasing the levels of vermicompost, dry matter yield and concentrations of total nitrogen (TN), phosphorus (P), iron (Fe), copper(Cu) and zinc (Zn) in corn shoots were significantly increased. But, due to the antagonistic relationship between manganese (Mn) and Zn or Fe,concentrations of Mn were significantly decreased. However, the concentration of Mn was in the sufficiency range. The highest dry matter yield and concentrations of nitrogen and phosphorus in corn shoot was observed at 30 g kg-1 vermicompost treatment, with 19, 10 and 20 % increase (compared to the control), respectively. The application of 30 g kg-1 vermicompost increased the concentrations of Zn, Cu and Fe by 41%, 90% and 75%, respectively and concentration of Mn decreased by 11.88%, compared to the control. Increasing the levels of water stress increased significantly the concentration of nutrients in corn shoot due to the reduction of corn biomass. The highest increase in nutrient concentrations was observed at 60% FC moisture level. Nitrogen and phosphorus concentrations in corn shoots by 12.5and 22.5% and Zn, Cu, Fe and Mn by 25, 83, 43and29% were higher compared to those of control (100% FC), respectively. The interaction effects of water stress and vermicompost on the concentrations of shoot N and Cu were significant and both were incresead by simultanoeus application of vermicompost and levels of water stress. The applicaion of 30 g kg-1 vermicompost (about 60 ton ha-1) under 60% FC moisture level increased significantly dry matter yield and the concentrations of nitrogen, phosphorus, zinc, copper and iron in corn shoot by 29%,5.5%, 23, 110, 41 and 71 percent compared to the control, respectively. However, because of the antagonistic relationships,the iron or manganese concentrations were reduced, but were yet in the sufficiency range. The use of 30 g kg-1 vermicompost under 80% FC moisture level Also increased significantly the concentrations of nitrogen, phosphorus, zinc, iron and copper by 9, 23, 24, 59 and 43 percent compared to the control, respectively.
Conclusion: The applicaion of 30 g kg-1 vermicompost increased significantly dry matter yield and the concentration of nitrogen, phosphorus, zinc, copper and iron in corn shoot under water stress treatments. In conclusion, the application of vermicompost mitigated the detrimental effects of water stress on corn dry matter yield and concentration of nutrients due to the positive effects of compost on physical, chemical and biological properties of the calcareous soil.
M. Bahraminia; M. zarei; abdolmajid ronaghi; R. Ghasemi
Abstract
A greenhouse experiment was conducted to evaluate the effectiveness of arbuscular mycorrhizal (AM) fungi in phytoremediation of zinc contaminated calcareous soil by vetiver grass. Experiment was a factorial arranged in a completely randomized design (CRD) with three replications. Two factors consisted ...
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A greenhouse experiment was conducted to evaluate the effectiveness of arbuscular mycorrhizal (AM) fungi in phytoremediation of zinc contaminated calcareous soil by vetiver grass. Experiment was a factorial arranged in a completely randomized design (CRD) with three replications. Two factors consisted of Zn levels (10, 150, 300 and 600 mg kg-1 as ZnSO4.7H2O) and AM fungi (control, Glomus intraradices, Glomus versiforme). Shoot and root dry weights decreased as Zn levels increased. Mycorrhizal inoculation increased those plant measured parameters compared to those of control. With increasing Zn levels, and mycorrhizal inoculation, Zn uptake of shoot and root increased. Root colonization with mycorrhizal inoculation increased, but decreased as Zn levels increased. Mycorrhizal inoculation increased zinc extraction, uptake and translocation efficiencies. Zinc translocation factor decreased as Zn levels increased, however inoculation with AM fungi increased it. Zinc extraction and uptake efficiencies of G. intraradices were more than G. versiforme,while zinc translocation efficiency and factor were vice versa.
S. Abdi; reza ghasemi; N.A. Karimian; M. Feizian
Abstract
Sum of exchangeable and solution forms of soil potassium is widely used to determine potassium availability for plants. Reliability of these methods is not enough in soils that contain 2:1 phyllosilicates. Additional to exchangeable potassium, nonexchamgeable potassium also has an important role in plant ...
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Sum of exchangeable and solution forms of soil potassium is widely used to determine potassium availability for plants. Reliability of these methods is not enough in soils that contain 2:1 phyllosilicates. Additional to exchangeable potassium, nonexchamgeable potassium also has an important role in plant nutrition. Limited information about availability and release kinetics of nonexchangeable potassium in calcareous soils of Fars province is available. For this purpose, some extractants including ammonium acetate, boiling nitric acid, 0.1M nitric acid, 2M sodium chloride and water were evaluated to prediction of potassium availability for corn in 10 calcareous soils of Fars province. Release kinetics of nonexchangeable potassium was studied using 15 successive 15-min extraction with 0.01M calcium chloride. Kinetics models describing nonexchangeable potassium release rate including zero order, first order, second order, third order, parabolic diffusion, power function and ellovich were evaluated. Results showed that 1M neutral amonium acetate, 0.1M aitric acid, water and 2M sodium chloride extractants had high correlation with corn potassium uptake. Amount of potassium released among studied soils was vary in the range of 243 to 814 mg kg-1. According to R2 and SE, kinetics of nonexchangeable potassium release was described with power function, parabolic diffusion and ellovich equations satisfactorily. According to this fact that constant rate of parabolic diffusion and ellovich models had significant correlations with corn potassium uptake, it is recommended that these two models are suitable for use in these studied soils.
