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.
mohsen azarnia; abbas biabani; Abdollatif Gholizadeh; Hamid Reza Eisvand; Ebrahim Gholamalipour Alamdari
Abstract
Introduction: The most important problems of farmers in arid and semi-arid regions are adequate nutrition, optimum rooting, emergence, establishment and optimal density, and ultimately plant yield. Using grain priming and mycorrhizal inoculation is effective strategies in these conditions. Priming can ...
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Introduction: The most important problems of farmers in arid and semi-arid regions are adequate nutrition, optimum rooting, emergence, establishment and optimal density, and ultimately plant yield. Using grain priming and mycorrhizal inoculation is effective strategies in these conditions. Priming can cause earlier growth of seedling, to increase emergence rate, emergence percentage, plant tolerance to drought and salinity stress, early flowering as well as to increase the quality and quantity of yield and nutrient absorption. Plant hormones such as salicylic acid and gibberellic acid can be used for priming. Regarding plant response to environmental stresses, salicylic acid, which is an important signal molecule, plays a key role in the regulation of several physiological processes such as growth and plant development, absorption of ions, emergence and photosynthesis. Gibberellic acid (GA3) has been shown to be involved in many physiological processes such as cell division activity of meristem regions, increase the cell length, emergence speed, and emergence percentage, seedling growth in field condition, early flowering and yield. Mycorrhizal inoculation increases the availability of nutrients especially plant phosphorus, concentrations of plant hormones (auxins, cytokinins and gibberellins), chlorophyll content, the efficiency of biological nitrogen fixation, assimilates allocation to host plant organs, the changes of root structure, and improve soil structure.
Materials and Methods: In order to evaluate the response of lentil to grain priming (without grain priming, hydro-priming, 100 ppm gibberellic acid, 100 ppm salicylic acid, 100 ppm gibberellic acid + 100 ppm salicylic acid) and soil mycorrhizal inoculation (non-inoculated control, inoculated with Glomus moseae and Glomus intraradices), a factorial experiment based on a completely randomized block design with four replications carried out in a greenhouse and research farm of the Gonbad Kavous University during 2013 and 2014. Various priming treatments - applied in the laboratory. Then, during planting, mycorrhizal inoculation treatment was kept in the closet place to the grains about 5 g per gram of grain (40 spores per gram). To determine the activity of roots (root length and number of nitrogen fixation nodes) 10 seedlings per pot were kept. Measured traits in the field condition were included the concentration and uptake of total phosphorus in aerial parts, concentration and total phosphorus uptake of grain, grain yield, and biological yield.
Results and Discussion: Variance analysis showed that different treatments of mycorrhizal inoculation, priming, and their interactions had significant effects on the studied traits such as the root length, number of nitrogen fixation nodules, phosphorus concentration of aerial parts, grain phosphorus concentration, grain phosphorus uptake, biological yield, and grain yield. In this study the highest root length (39.5 cm), nitrogen fixation nodules (114), aerial parts phosphorus uptake (12.1 kg/h) were obtained under combined treatment of G. intraradices inoculation+ 100 ppm gibberellic acid. While the aerial parts phosphorus concentration (0.24%) and grain phosphorus uptake (22.8 kg/ha) were higher due to using combined treatment of mycorrhizal G. Moseae + hydro-priming. Hormonal priming with salicylic acid increased grain yield and biological yield significantly over the other hormonal priming and control. Hydro-priming had a significant and positive effect on grain yield in three levels of bio-fertilizer. Results of salicylic acid treatment were similar to the results of hydropriming. Influence of hormones, especially gibberellic acid in grain causes more activities in some emergence catalytic enzymes, the emergence speed, emergence percentage and root elongation. These effects may be inconspicuous in irrigated cultivation, but it can lead to the survival of plants in the dry farming situation. In this study, gibberellins increased the radicle length and the number of nitrogen fixation nodules. It may be an important factor in increasing the quality and quantity of grain yield of lentil. Various treatments of salicylic acid had a moderate effect. More positive effects were obtained when these treatments applied to the form of combination. The most applied treatments in this experiment such as mycorrhizal and priming treatments and their interaction had a positive effect on quality and quantity of grain properties of lentil aerial parts. This positive effect may be due to availability of some nutrients which is supplied using priming treatments, microorganisms, secretion of growth promotion and the change of root structure.
Conclusion: In the present study inoculation of both fungi and various treatments of priming had a positive effect on the studied traits individually, but the higher effects of them were found in the combined treatments. The effect of G. intraradices + hydro-priming was more outstanding. Overall, the present study indicated that the various treatments of bio-fertilizer and priming increased the root length and nitrogen fixation. Therefore, the absorption of nutrients was increased. It could be concluded that synthesis fertilizer is unnecessary.
