Taleb Nazari; mojtaba barani; Esmaeil dordipour; Reza Ghorbani nasrabadi; Somayeh Sefidgar shahkolaie
Abstract
Introduction: Fe is the first identified micronutrient for crops and required in higher amount than other micronutrients. Fe plays important roles in enzyme metabolism, protein metabolism, chlorophyll construction, chloroplast evolution, photosynthesis, respiration and reduction-oxidation reaction as ...
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Introduction: Fe is the first identified micronutrient for crops and required in higher amount than other micronutrients. Fe plays important roles in enzyme metabolism, protein metabolism, chlorophyll construction, chloroplast evolution, photosynthesis, respiration and reduction-oxidation reaction as well as organic acids metabolism. Iron, as an essential micronutrient, has great contribution in important antioxidant enzymes activity and through which affects plant tolerance against environmental stresses. Plant enzymes including superoxide dismutase, catalase and glutathione peroxidase are among the most important enzymes scavenging the hydrogen peroxide have iron in their structure, so they affected by iron deficiency. In this study, the effect of soil, foliar and fertigation application of humic acid on iron availability, chlorophyll types and superoxide dismutase, catalase and glutathione peroxidase enzymes in canola (Hyola 308) were evaluated.
Results and Discussion: Results showed that highest total iron content in plant leaves was obtained in 0.4 percent foliar application and the lowest was belonged to control treatment. Highest iron content in plant stem and active iron was obtained in humic acid application through irrigation at 2000 mg L-1 by 85 and 44.86 mg kg-1, respectively, and lowest amounts were obtained in control by 54.62 and 20.40 mg kg-1. Also, greatest concentration of chlorophyll a, chlorophyll b and total chlorophyll were recorded under0.4 percent humic acid foliar application by 3.58, 1.79 and 5.37 and the lowest chlorophyll contents were associated to control. Highest activities for plant enzymes superoxide dismutase and glutathione peroxidase were obtained under0.1 percent foliar application of humic acid by 4.20 and 1.95 (Iu/gr. FW) and the highest activity for catalase enzyme by 4.46 Iu/gr FW in 1000 mg L-1 humic acid through was irrigation and the lowest enzyme activity obtained in control treatment. Findings showed that application of various levels of humic acid increased plant enzyme activity compared to control in all of three application method (soil, foliar and application through irrigation water). Increasing humic acid concentration decreased enzyme activities. Also, there was negative correlation between activity of plant enzymes and concentation of chlorophyll types and active iron.
Conclusions: Active iron and antioxidant enzymes represent iron status within cell cytoplasm. Based on the results of this study, active iron concentration and activity of antioxidant enzymes are appropriate indices for evaluating plant tolerance to iron deficiency compared to assessing total iron content in leaves.
Somayeh Sefidgar; Mojtaba Barani Motlagh; farhad khormali; Esmael Dordipour
Abstract
Introduction: Soil pollution with heavy metals have become a global concern because of its damaging effects on the environment, including human health, toxicity in plants and long-term effects on soil fertility. Heavy metals stress in plants is characterized by decrease in photosynthesis, nutrient uptake, ...
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Introduction: Soil pollution with heavy metals have become a global concern because of its damaging effects on the environment, including human health, toxicity in plants and long-term effects on soil fertility. Heavy metals stress in plants is characterized by decrease in photosynthesis, nutrient uptake, damaging of roots and finally plant death. Lead (Pb) is found to be the most dangerous heavy metal, responsible for reduced soil fertility and elevated environmental pollution. Lead toxicity causes the inhibition of seed germination and exerts adverse effects on growth and metabolic processes of plants, which retards plant and crop production. The overproduction of reactive oxygen species (ROS) is the best indicator for secondary stress, which results in a number of toxic effects on biochemical processes in many plant cells. The overproduction of ROS due to Pb stress brings about changes in cellular membrane permeability, which in turn damages organelles such as nuclei, mitochondria, and chloroplasts in plant cells which decreased plant growth and yield. Chemical stabilization is an in situ remediation method that uses inexpensive amendments to reduce contaminant availability in polluted soil. The aim of this study was to investigate the immobilization of lead in a calcareous contaminated soil using two types of biochar as organic and Pumice, Leca, Zeolite and Bentonite as inorganic amendments.
Materials and Methods: In order to investigate the effect of organic amendments (biochar 640°C, and biochar 420°C) and inorganic amendments (Pumice, Leca, Zeolite and Bentonite) on Pb stabilization in a contaminated soil (1500 mg/kg), a greenhouse experiment using maize plant was carried out. This experiment was conducted in a completely randomized design consisting of 6 types of amendments (Pumice, Leca, Zeolite, Bentonite, Biochar 420°C, and Biochar 640°C) and at 1% and 5% levels of each amendment (12 amendments plus 1 control). The experimental treatments were incubated for 3 months. At the end of incubation time, the potential bioavailability of Pb in non-amended and amended soils was assessed by chemical extractions, as: extraction with DTPA, with ammonium acetate and with ethylenediaminetetraacetic acid (EDTA). After the end of incubation time, the pots were transferred to a greenhouse and in each pot five maize seeds were planted and then reduced to three seedlings in each pot after germination. After 3 months, all the plants were harvested. The Pb concentration in each plant, its biomass, its chlorophyll and its antioxidant enzyme activities levels were analyzed. All statistical analyses were performed using SAS software. Means of different treatments were compared using LSD (P ≤0.05) test.
Results and Discussion: The results indicated that the addition of amendments to soils reduced the concentration of Pb extracted with DTPA and EDTA. The 5% biochar 640 had the greatest reduction effect on DTPA-extractable Pb. The smallest concentration of Pb in the leaves and root of maize plant was observed in treated soil with organic amendments (biochar 640°C, and biochar 420°C) and treated with 5% zeolite, respectively. The highest increase in plant growth parameters like SPAD value, leaf area, plant height, number of leaves per plant, dry biomass yield and dry matter of roots were observed in organic amendments compared to the control. The application of 5% amendments in soil caused a significant increase in plant height and number of leaves as compared to control. The increase in growth and biomass of zea mays L. under various amendments might be due to decreased bioavailable Pb concentrations in soil amended which may be attributed to reduced Pb toxicity through improvement of soil fertility. Also, the application of amendments resulted in a significant increase in antioxidant enzyme activities such as superoxide dismutase (SOD), catalase (CAT), peroxidase (PX), and ascorbate peroxidase (ASP) in maize plants compared to the control. The increase of leaves enzyme activities with addition amendments may be due to a lower Pb accumulation in leaves because excess Pb generates free radicals and reactive oxygen species (ROS) those causes oxidative stress in plants.
Conclusions: The results indicated that the application of amendments were successful in lowering the potential bioavailability of Pb in the soils. The 5% biochar 640 treatment had the greatest reduction effect on extractable Pb. The application of amendments decreased the uptake and accumulation of Pb in maize plants, via the reduction of DTPA- extractable Pb. The amendments also significantly increased leaves antioxidant enzyme activities and photosynthetic pigments compared to the control.
