## 1 Introduction  
One of humanity's greatest challenges is how to sustainably feed a large population, especially in China [1, 2]. _Tritcium aestivum_ L. is one of the most important grain crops in the world [3], and increasing its yield is an effective way to solve the problem of food shortage caused by rapid population growth [4, 5]. As crop yields continue to improve, the usage of traditional organic fertilizers to increase the availability of major nutrients (N, P, and K) has been increasing. However, effective supplementation of trace nutrients necessary for plant growth (particularly for iron) is neglected in large production systems [6, 7, 8]. The utilization of these conventional fertilizers, which usually lack iron, can lead to iron deficiency in the soil-plant system. Such a deficiency not only decreases agricultural yields but also impacts human health through \"hidden hunger\", an insidious form of micronutrient (Fe) deficiency that can hinder growth, weaken immune function, and lead to anemia [9, 10]. Iron deficiency in soil-plant systems is a widespread challenge in agricultural production worldwide and a scientific issue that needs to be further addressed. Iron is a metal element that is widely distributed in nature, with a high abundance in the Earth's crust. The total iron content in soil typically ranges from 1% to 10%. However, it is not readily available because of its low solubility [11]. According to statistics, potential iron deficiency affects approximately 40% of the world's arable land [12]. Iron is an essential trace mineral element for the growth and development of plants. It serves as an integral component of vital enzymes, including cytochrome, cytochrome oxidase, and catalase [13]. When the soil is deficient in iron, it significantly impacts the growth and development of crops [14], leading to reduced yield and quality [15]. Two methods, leaf spraying iron fertilizer and soil micro-fertilizer, are commonly employed to resolve the symptoms of iron deficiency in _Tritcium aestivum_ L. in soils. It has been shown that the micro-fertilizer of iron carrier chelates is not affected by the pH value and Ca++ ion concentration of soil medium, which is of great significance for calcareous and alkaline soils [2,16]. However, excessive application of soil micro-fertilizer can result in resource wastage and environmental quality issues such as heavy metal pollution in surface soil and contamination of shallow groundwater, posing health risks [17]. For example, excessive iron contamination is widespread (>0.3 mg/L) [18]. Over 50 mg/L iron will cause toxicity to microorganisms and significantly inhibit microbial activity [19]. The threshold of soil micro-fertilizer usage to ensure the improvement of soil quality without wasting resources remains unknown. The iron ion has an 18-electron shell, and its high electrostatic field makes it readily form complex ions [20]. To date, the physiological mechanism of iron uptake and utilization by plants has been extensively documented in the literature [21; 22; 23; 24; 25]. [PERSON] was the first to propose the Mechanism I and Mechanism II systems of iron uptake for higher plants under iron deficiency [26]. The typical _Tritcium aestivum_ L. vegetation studied in this research belongs to mechanism II plants, which are herbaceous monocotyledonous grasses capable of adapting to high-pH soil. In an iron-deficient environment, these plants can induce the production of high-iron transporters (MAs) in the _Tritcium aestivum_ L. rhizosphere and secrete them to activate insoluble iron in the rhizosphere, forming a stable octahedral Fe\({}^{3+}\) chelate, i.e., Fe\({}^{3+}\)-MAs, which is then specifically absorbed by the rhizosphere to adapt to iron deficiency. After the plant root system absorbs iron from the environment, the plant senses its iron nutritional status and regulates the distribution of iron through its own signaling and regulatory system [23]. Previous research has indicated that iron typically exists in plants in the form of chelates.