K. Kiani Jam; M.R. Bihamta; D. Habibi; A. Asgharzadeh; A. Saremirad
Abstract
Introduction: Nowadays, increasing soil contamination by heavy metals is one of the most important issues around the world, and is the focus of attention. Lead as the most dangerous heavy metal and persistent chemical pollutant affects the environment, especially the metabolic and physiological activities ...
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Introduction: Nowadays, increasing soil contamination by heavy metals is one of the most important issues around the world, and is the focus of attention. Lead as the most dangerous heavy metal and persistent chemical pollutant affects the environment, especially the metabolic and physiological activities of organisms and ultimately cause serious damage to the environment and human health. The purpose of this study was to investigate the effect of mycorrhizal fungus (Rhizophagus irregularis) on some biochemical traits of 10 wheat genotypes in three different concentrations of lead heavy metal (0, 218 and 437 ppm) in soil.
Material and Methods: The present study was conducted as factorial experiment based on randomized complete block design with three replications. The factors included lead in three concentrations (0, 218 and 437 mg / kg), mycorrhizal inoculum (addition and no addition), and 10 wheat genotypes (Shiraz, Sepahan, Sirvan, Back Cross Roshan, Marvdasht, Sivand, Bahar, Pars, Roshan, and Pishtaz). Soil samples were prepared from a depth of 0-25 cm of the research farm of Islamic Azad University, Karaj Branch. Samples were taken randomly. After soil drying and passing through a 2 mm sieve, they were transferred to the soil science laboratory to determine some of the physical and chemical properties. According to the soil test results, the soil was sandy loam, a semi-light soil with 25% clay, 25% silt and 50% sand, with pH = 7.49 and salinity of 1.63 dS. m-1, and also free of heavy metals. The soil was sterilized for four hours by an autoclave at the temperature of 121 °C and a pressure of 1.5 atm. After soil preparation, the lead was added to the soil at three concentrations of 0, 218 and 437 ppm, and stored in a pre-embedded bag with 60% moisture content to achieve a two-week equilibrium. In order to inoculate the mycorrhizal fungus, after removal of 3-4 cm from the soil surface, Rhizophagus irregularis (35 g) was added to the soil surface, then 30 to 40 seeds were placed on the soil surface and covered with soil. In the control samples without mycorrhizal fungus, a certain amount of mycorrhizal fungus placed at 105 ºC to kill the fungus and then added to the pots.
Results and Discussion: Malondialdehyde concentration increased by increasing the concentration of lead. The highest concentrations of proline were belonged to the level 218 ppm of lead, in Pars cultivar in both treatments of with and without mycorrhiza fungus as well as Sirvan cultivar in the treatment of without fungi, respectively. The activity of Catalase was highest in the treatment of 218 ppm of lead without fungus. Roshan cultivar also showed high levels of ascorbate peroxidase activity in 218 ppm of lead. Similar to cultivar, BC Roshan and Pishtaz cultivars also showed high ascorbate peroxidase activity in this concentration of lead. The amount of hydrogen peroxide was reduced by changing the concentration of lead from 0 to 218 ppm, while its amount increased at 437 ppm concentration. With increasing lead concentration, the amount of chlorophyll a decreased while chlorophyll b increased. Using mycorrhizal fungus, the amount of malondialdehyde, proline and hydrogen peroxide and catalase content decreased compared with control. It seems that lead, due to its concentration in the environment, leads to the induction of oxidative stress and the formation of free radicals and thus change in the amount of biochemical traits of wheat such as malondialdehyde, proline, hydrogen peroxide and chlorophyll a and b and activity of catalase and ascorbate peroxidase. The genotype of the plant is very important factor in tolerating the toxicity of lead, and it deals with various protective mechanisms. Not only the plant genotype but also environmental factors such as the use of mycorrhizal fungus are effective in reducing the harmful effects of lead, and helps plants tolerate the stress caused by lead toxicity.
Conclusion: Lead in the soil causes changes in the biochemical content of wheat cultivars. The amount of change depends on the plant's genotype, lead concentration, and other factors in the soil, such as symbiotic fungi. As shown in the present study, mycorrhizal fungus was effective in eliminating the negative effects of lead during symbiotic with wheat. It is suggested further studies to determine the concentration of lead and even other heavy metals in wheat genotypes and to compare with Iranian national standards in order to overcome the concerns about the entry of these metals into the diet.
Sabireh Golshahi; Ahmad Gholamalizadeh Ahangar; Noshin Mir; Maryam Ghorbani
Abstract
Introduction: First and the most important requirement of human being is food and food supply, which is directly, or indirectly associated with agriculture. Iron is a critical element for the growth, expansion and survival of the plant, since multiple metabolic and a physiological process is essential ...
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Introduction: First and the most important requirement of human being is food and food supply, which is directly, or indirectly associated with agriculture. Iron is a critical element for the growth, expansion and survival of the plant, since multiple metabolic and a physiological process is essential for the proper functioning. Agricultural areas in the world have a high pH in soil, which in turn decreases iron absorption by plants. Iron deficiency depending on many soil and environmental factors as well as plant genetic that in turns can decrease the yield and product quality. One method of overcome iron deficiency in plants is foliar application. A foliar application of iron fertilizer in agriculture is the common practice, especially in soils that accompanied with iron deficiency. The proper use of various types of fertilizers is the main solution to improve and maintaining soil fertility and increase crop production. The objective of this study is to evaluate the effect of foliar application of iron sources on growth parameters, concentration and absorption of iron in shoot and root and enzymes activity of catalase (CAT), ascorbate peroxidase (APX) and guaiacol peroxidase (GPOX) on forage sorghum plant to determine the best combination of iron fertilizer.
Materials and Methods: An experiment was conducted in a completely randomized design with factorial arrangement and three replications in greenhouse condition on forage sorghum (Sorghum Bicolor (L.) Moench) varieties of speed feed. The treatments included two levels of iron (0.25 and 0.5 g Fe.L-1 with Control (C)) from nine iron sources (Iron chelate (F1), Iron sulfate (F2), Iron oxide nanoparticles (F3), Monodisperse iron oxide nanoparticles (F4), Green nano iron (F5), Polymeric iron chelate (F6), Polymeric iron sulfate (F7), Polymeric iron oxide nanoparticles (F8) and Polymeric monodisperse iron oxide nanoparticles (F9)). The soil was obtained from educational and research greenhouses of Zabol university and after air drying and sieving passing 2 mm, some physical and chemical characteristics of soil such as texture, pH, electrical conductivity, cations exchange capacity, calcium carbonate equivalent, organic matter, total nitrogen contents, available P contents, available K contents and available Fe contents was measurement. Spraying of iron resources performed in two stages (4 leaf and the two weeks after first spraying). After two months of planting, the shoot cut from the surface of the soil and roots of the plants collected. Some parameters such as shoot and root dry weight, chlorophyll a, b and carotenoids, iron concentration in shoot and root, iron absorption in shoot and root, and activity of the enzyme (catalase, ascorbate peroxidase, guaiacol peroxidase) was measured. The experimental data examined using Excel and SAS 9.4 statistical software and the averages were compared using Duncan’s Multiple Range Tests at 0.01 and 0.05 significance level.
Results: Results analysis of variance indicated that the interaction effects between iron resources and iron level on the dry weight of shoots and roots, chlorophyll a and b, iron absorption in shoots and roots, enzymes guaiacol peroxidase. Ascorbate peroxidase and catalase were significant at the level of 5 percent and iron concentrations in shoots and roots were significant at the level of 1 percent. The carotenoid content in leaves in the simple effects of iron resources was significant at the level of 5 percent. According to the results, foliar application of treatments on dry weight of shoots and roots, Fe concentration and Fe absorption by shoots and roots, chlorophyll a, b and the enzyme activity of APX, GPOX in addition CAT were significantly increased compared to Control. Foliar application at 0.25 g Fe.L-1, chlorophyll b in the treatment of monodisperse iron oxide nanoparticles, Fe concentration and Fe absorption in the shoots in treatments of polymeric iron sulfate and polymeric iron chelate, respectively. Fe concentration and Fe absorption in the roots in treatment of polymeric monodisperse iron oxide nanoparticles and APX activity in iron chelate treatment increased significantly compared to control. At level of 0.5 g Fe.L-1, dry weight of shoots in the treatment of iron chelate, dry weight of roots and CAT enzyme in the treatment of green nano iron, chlorophyll a in the treatment of polymeric iron chelate and GPOX enzyme in the treatment of monodisperse iron oxide nanoparticles were compared with the control increased significantly. The simple effects of iron sources indicated that the highest level of carotenoids observed in the foliar application of polymeric iron chelate.
