The Effect of Foliar Application of Iron Sources on Growth Parameters, Iron Concentration and Activity of Some Enzymes of Sorghum

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.
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 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.