Soil science
F. Shahabi; R. Khorassani; Z. Gheshlaghi
Abstract
Introduction
This study examined the influence of glutathione on iron availability in calcareous soils and its effect on the iron availability from various iron sources for peanut plants. Calcareous soils, prevalent in many regions, challenge nutrient availability, particularly for micronutrients such ...
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Introduction
This study examined the influence of glutathione on iron availability in calcareous soils and its effect on the iron availability from various iron sources for peanut plants. Calcareous soils, prevalent in many regions, challenge nutrient availability, particularly for micronutrients such as iron, manganese, and zinc, owing to their high pH levels. Despite adequate iron levels in these soils, plant accessibility remains restricted, often resulting in iron deficiency symptoms, such as chlorosis, due to impaired chlorophyll synthesis. Various strategies, including the development of resistant cultivars, organic amendments, and mineral or chelated iron fertilizers, have been explored to mitigate iron deficiency. Chelated iron fertilizers, especially iron sequestration (EDDHA) agents, are commonly used in calcareous soils to enhance iron availability in plants. However, their environmental impact and cost-effectiveness are concerns, prompting interest in alternatives such as iron oxides, which are cost-effective and environmentally friendly. Studies have suggested that iron oxides, particularly magnetite nanoparticles, support plant growth and enhance the availability of iron. Additionally, growth stimulants, such as glutathione (a tripeptide with antioxidant properties), have been investigated for their potential to alleviate iron deficiency. Glutathione not only boosts plant defense mechanisms but also improves reactive oxygen species availability. Recent studies have shown that the foliar application of glutathione in iron-deficient plants can significantly increase total iron uptake and enhance photosynthesis. This study aimed to investigate the effects of glutathione on iron bioavailability from various iron sources and growth parameters in peanuts cultivated in calcareous soils.
Materials and Methods
The experiment was conducted in a greenhouse at the Agricultural Research Center of Ferdowsi University of Mashhad and, employed a completely randomized factorial design with three replications. The factors were iron sources (control, iron sequestration (EDDHA), iron oxide, and iron filings) and glutathione foliar application (0, 1, and 2 mM, four times per growth season: 29, 38, 42, and 48 days after planting). Soil was sampled from a farm, and some of its physical and chemical properties were analyzed using conventional methods. Macronutrients were added at the recommended dosage to minimize interference with iron treatment. The iron levels were 0 and 50, 1370, and 108 mg kg-1 for sequestration, iron oxide, and iron filings, respectively. Glutathione foliar treatments were applied at four growth stages (29, 38, 42, 48 days after planting) in concentrations of 0, 1, and 2 mM. The plants were grown in pots with soil moisture maintained at the field capacity. After 66 days, the plants were harvested, and parameters such as dry shoot weight, total iron uptake, and nitrogen content were measured. The iron content in plants was determined using atomic absorption spectroscopy, and nitrogen was quantified applying the Kjeldahl method. Statistical analyses were conducted using SAS software, and mean comparisons were performed using Duncan's test at the 5% significance level.
Results and Discussion
The study revealed that glutathione, either alone or in combination with iron sources, notably improved peanut plant growth and iron uptake. Iron sequestration (EDDHA) was the most effective treatment, significantly increasing dry shoot weight, particularly when combined with 2 mM glutathione. The combination of glutathione and iron treatment substantially boosted total iron uptake in both the shoots and roots of peanut plants. Notably, iron sequestration (EDDHA) with glutathione resulted in a 20% increase in shoot iron uptake and a 34.3% increase in shoot nitrogen uptake compared to glutathione treatment alone. Glutathione application also enhanced iron filings, leading to a 55.6% increase in root iron uptake by shoots and a 50.6% increase in iron concentration in shoots, as extracted by phenanthroline. The results indicated that glutathione improved and facilitated iron translocation from the roots to the shoots. Iron filings, a cost-effective iron source, showed significant results when paired with glutathione, enhancing both shoot dry weight and iron uptake. This synergy between glutathione and iron treatments suggests that iron sequestration (EDDHA) is more effective when combined with glutathione, resulting in alleviating deficiency symptoms of iron, such as chlorosis, and promoting overall growth.
Conclusion
This study underscores the positive impact of glutathione on iron availability and growth in peanut plants grown in calcareous soils. Applying glutathione significantly increased iron uptake in both shoots and roots, nitrogen uptake, and plant biomass. Iron sequestration (EDDHA), combined with glutathione, emerged as the most effective treatment, improving shoot iron and nitrogen uptake by 20% and 34.3%, respectively. Additionally, glutathione enhanced the efficacy of iron filings, an economical iron source, suggesting its potential as an alternative to expensive iron fertilizers. Glutathione application also reduced chlorosis and improved iron translocation from roots to shoots, supporting its role in enhancing iron nutrition in crops grown in iron-deficient soils. This study offers insights into the role of glutathione in managing iron deficiency stress and recommends further exploration of optimal application rates and effects on diverse crops and soil conditions.
