Chelates in Plants Explained

Milosh Potikj | September 20, 2023 | 11 MIN READ

In the world of plants, chelates play a vital role in their survival and growth. These organic compounds, often derived from substances like humic acid or amino acids, are essential for ensuring the availability of nutrients, especially metals, in plant tissues. Chelation, the process by which these compounds bind to metal ions, helps facilitate the transportation and uptake of essential elements from the soil to different parts of the plant, such as the roots and leaves.

One of the most well-known examples of chelation in plants is the chelation of iron ions. Iron deficiencies commonly occur in plants, especially in alkaline or acidic soils, where the availability of iron can be limited. However, through chelation, plants can overcome this obstacle and enhance iron uptake. Chelated iron, typically in the form of a complex with organic acids like citric acid, allows for easier absorption through the roots, promoting healthy growth.

What are Chelates?

Chelates play a vital role in plant nutrition by converting metal micronutrients into a water-soluble form that plants can easily absorb. But what exactly are chelates, and how do they work?

Chelates are organic compounds that act as natural "grappling hooks" for metal ions in plant tissues. They consist of a central atom, usually a metal ion, surrounded by multiple bonds from organic ligands. Common organic compounds used as ligands in chelates include amino acids, organic acids like citric acid, and humic acid derived from organic matter.

The key role of chelates is to prevent metal ions from reacting with oxygen or other ions, which would make them less available for plants. By forming chelates, the metal ions are securely bound and protected from unwanted reactions. This protection maintains their stability and allows for a more efficient and controlled utilization by plants.

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The Role of Chelates in Plant Growth and Development

Chelates play a vital role in the growth and development of plants by enhancing nutrient absorption, protecting against nutrient loss, and contributing to overall plant health and productivity. These organic compounds form complexes with essential metals, such as iron and zinc, which are crucial for various physiological processes in plants.

  1. Chelates improve nutrient absorption by increasing the availability and solubility of essential metals in the soil. Chelating agents, like amino acids and organic acids, bind to the metal ions and prevent them from becoming immobilized and unavailable to plant roots. This mechanism ensures efficient uptake of vital nutrients, especially under conditions of nutrient deficiency in the soil.
  2. Chelates protect against nutrient loss by preventing the precipitation and leaching of essential metals. In alkaline soils, iron, for example, can become unavailable to plants due to its insolubility. Chelated iron, however, remains soluble and easily accessible to plant roots, ensuring iron uptake and preventing deficiencies.
  3. Chelates contribute to overall plant health and productivity by serving as a defense mechanism against abiotic stresses, such as heavy metal toxicity. Chelation helps plants tolerate high concentrations of toxic metals by reducing their bioavailability and minimizing their negative impact on plant tissues.

Types of Chelates

Types of Chelates

Different types of chelates, such as amino acids, citric acid, and humic acid, form complexes with metal ions, particularly iron, in both acidic and alkaline soils. These chelates improve iron availability to the plant roots, ensuring proper growth and development.

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Organic Compounds

Organic compounds play a vital role in maintaining the health and growth of plants. One important function of organic compounds in plants is their ability to chelate or bind with metal ions, such as iron, in the soil. Chelation refers to the process of forming a complex between a metal ion and a ligand, in this case, an organic compound.

Among the various organic compounds involved in chelation, citrate, malate, oxalate, and dicarboxylic acid malate are key players. These organic acids are produced by plants and play crucial roles in plant metabolism, stress tolerance, ion balance, and nutrient uptake.

Citrate, for example, enhances the availability of nutrients, particularly iron, by forming chelated complexes with iron ions. This is particularly important in alkaline soils where iron availability can be limited. Malate and oxalate also play important roles in the uptake and translocation of nutrients, as well as in the regulation of ion balance in plant tissues.

Dicarboxylic acid malate is known to be involved in plant adaptation to environmental changes and acts as a defense mechanism against abiotic stresses. Through chelation, these organic compounds help plants cope with metal toxicity and nutrient deficiencies, ensuring their survival and growth.

Humic Acid

Humic acid is a widely studied organic compound found in plants that plays a vital role in plant growth and development. It is typically a complex mixture of organic compounds that naturally occur as a result of decaying plant and animal matter.

One of the key benefits of humic acid is its ability to increase nutrient availability in the soil. It acts as a chelating agent, binding to essential minerals and nutrients in the soil and forming stable complexes that are easier for plants to absorb. This enhances the efficiency of nutrient uptake by plant roots and reduces the risk of nutrient deficiencies.

Additionally, humic acid improves soil structure by promoting the formation of aggregates. This leads to better water retention and aeration, allowing plant roots to access water and oxygen more efficiently. Improved soil structure also enhances the microbial activity in the soil, promoting the breakdown of organic matter and nutrient cycling.

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Amino Acids

Amino acids play a vital role in the chelation and detoxification processes in plants, especially in response to metal stress. When plants are exposed to high levels of heavy metals, such as iron, copper, or zinc, they can suffer from nutrient deficiencies and other abiotic stresses. To combat this, plants have developed defense mechanisms that involve the synthesis and accumulation of specific amino acids.

Several amino acids have been identified as crucial players in metal chelation and tolerance in plants. These include glycinebetaine, proline, histidine, cysteine, arginine, glutamate, nicotianamine, and polyamines. These amino acids act as chelating agents by binding to heavy metal ions and forming stable complexes, preventing their toxicity and allowing for their sequestration or transportation within plant tissues.

For example, histidine and cysteine are known to form complexes with heavy metal ions, such as iron, and enhance their uptake mechanism in plant roots. Glycinebetaine and proline, on the other hand, improve plant tolerance to metal stress by acting as osmoprotectants, maintaining cellular homeostasis under unfavorable conditions.

Iron Deficiencies and Iron Ions

Iron deficiencies are a common problem in plant nutrition, as iron ions play a vital role in various biochemical processes. However, iron ions are often present in insoluble forms in the soil, making it challenging for plants to uptake them. Fortunately, plants have evolved certain mechanisms to overcome this issue.

One mechanism is the solubilization and uptake of iron in plant roots. Plant roots release chelating substances, such as phytosiderophores, to solubilize iron ions from insoluble forms. These chelating substances bind to the iron ions, forming complexes that are more easily absorbed by the roots.

Central Atom

In plants, chelation involves the formation of stable complexes between a central atom and chelating ligands. The central atom plays a crucial role in this process by coordinating with the ligands to form a coordination bond. This bond is what holds the chelate complex together.

The choice of central atom is important as it determines the stability and properties of the chelate complex. Different central atoms can have different affinities for ligands, resulting in varying degrees of stability. For example, in the case of iron deficiencies in plants, chelated iron is often used to improve iron availability. Iron ions can chelate with organic compounds such as amino acids, citric acid, or humic acid to form stable complexes. These complexes prevent iron from precipitating in alkaline soils or binding to other compounds in acidic soils, ensuring that it remains soluble and available to the plant.

The stability of chelate complexes is also affected by the equilibrium constant, which is dictated by the central atom-ligand interaction. Additionally, the properties of chelate complexes, such as their solubility and ability to be transported within plant tissues, are determined by the central atom and its coordination with the ligands.

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Chelated in Hydroponic Solutions

Chelation plays a vital role in the world of hydroponic gardening, ensuring that plants receive the necessary nutrients for growth. Chelation refers to the binding of metal ions to organic compounds, forming stable complexes that are more easily absorbed by plants. In hydroponic solutions, both synthetic chelates and naturally occurring chelating agents are used.

Synthetic chelators, such as ethylenediaminetetraacetic acid (EDTA), are commonly employed in hydroponics. These chelates have a central atom that can bind to metal ions, improving their availability in the solution. When plants take up these synthetic chelates, they release the metal ions back into the solution for further use.

On the other hand, naturally occurring chelating agents found in organic matter, such as fulvic acid and humic acid, help plants in a different way. These natural chelates have the ability to be absorbed by the plants' tissues, where they enhance nutrient uptake and aid in the plants' adaptation to abiotic stresses.

In a hydroponic garden, synthetic chelates are commonly used due to their high stability and availability. However, many hydroponic gardeners also opt for organic and sustainable practices, preferring to use naturally occurring chelating agents. These natural chelators not only provide essential nutrients to the plants but also help in building healthier and more resilient plant tissues.

Benefits of Chelated Iron to Plants

Benefits of Chelated Iron to Plants

With its remarkable benefits, chelated iron is revolutionizing plant nutrition, ensuring healthy and resilient plants in the face of diverse challenges.

Nutrient Deficiency Prevention

Nutrient deficiency prevention is crucial for the optimal growth and development of plants. Chelation plays a vital role in ensuring the availability of essential micronutrients such as iron, boron, manganese, zinc, and molybdenum.

Chelation refers to the process by which organic compounds, such as amino acids and organic acids like citric acid, form complexes with metal ions. These complexes, known as chelates, help to enhance the solubility and availability of micronutrients to plant roots.

In the case of iron deficiency, for example, chelated iron is more readily absorbed by plant roots compared to other forms of iron. Chelated iron can be taken up by plants in both acidic and alkaline soil conditions, providing a key solution for iron deficiencies in various environments.

Several factors influence the availability of micronutrients in soils. Soil pH, moisture, and aeration affect the solubility and uptake of these nutrients. Additionally, the presence of organic matter and interactions with other nutrients can either enhance or hinder the availability of micronutrients to plants.

Chelation helps plants overcome the limitations imposed by these factors. By forming stable chelates, plants can acquire the required micronutrients efficiently, even in unfavorable soil conditions.

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Vital Role in Roots Systems

Chelates play a vital role in root systems of plants by facilitating the absorption and transport of essential nutrients, particularly iron. In order for plants to thrive, they need an adequate supply of iron, which is crucial for various physiological processes. However, iron is often present in forms that are not readily available for uptake by plant roots. This is where chelation comes into play.

Chelates are organic compounds that form complex structures with metal ions, such as iron. They act as chelating agents, binding to the iron ions and creating stable structures known as chelated iron. This complex is more soluble and bioavailable, making it easier for plant roots to absorb.

When chelated iron is present in the root system, it not only enhances iron uptake but also allows for efficient transport within the plant tissues. This prevents iron deficiencies, which can lead to stunted growth and diminished crop yields.

Increased Iron Availability in Alkaline Soil

Iron is an essential nutrient for plants, playing a vital role in various metabolic processes. However, its availability to plants can be limited, especially in alkaline soil. The high pH levels in alkaline soil affect the solubilization and uptake of iron by plants. In alkaline conditions, iron ions (Fe3+) form insoluble compounds, making them inaccessible to plant roots. But certain factors contribute to the increased availability of iron in alkaline soil.

Chelates, such as organic acids and amino acids, play a key role in chelating iron and making it more accessible to plant roots. These organic compounds form stable complexes with iron ions, preventing their precipitation and keeping them soluble in alkaline soil. Organic acids like citric acid can dissolve insoluble iron compounds, releasing iron ions for plant uptake. Amino acids, including bidentate phosphine, also form chelates with iron, increasing its availability.

Chelates have a crucial function in the uptake mechanism of iron by plants. They enhance the solubility and mobility of iron, allowing it to be transported from the soil into the plant tissues. Chelated iron complexes are more easily absorbed by root hairs, ensuring an adequate supply of iron to the plant. This is especially important for iron-demanding crops like Zea mays, where iron deficiencies can severely affect growth and yield.

Understanding the role of chelates in iron availability is of utmost importance in plant nutrition. By promoting the chelation of iron, plants can overcome iron deficiencies and better adapt to alkaline soil conditions. This knowledge can help researchers and farmers develop strategies to improve iron uptake and optimize crop productivity in alkaline environments.

Applications of Chelation in Plant Science

Chelation plays a vital role in plant science and has various applications. Here are some key applications of chelation in plant science:

  1. Improving nutrient availability: Chelates, such as amino acids and organic acids, form stable complexes with metal ions, making them more available for plant uptake. This is particularly important in acidic or alkaline soils where nutrient availability can be limited.
  2. Enhancing iron intake: Iron deficiency is a common problem in plants, especially in alkaline soils. Chelated iron, such as iron-EDTA or iron-DTPA, increases iron availability and assists in preventing iron deficiencies.
  3. Detoxifying heavy metals: Chelation can help plants tolerate and detoxify toxic metals by forming complexes with the metal ions. This defense mechanism helps reduce the harmful effects of heavy metal accumulation in plant tissues.
  4. Enhancing plant adaptation to abiotic stresses: Chelation of organic compounds, such as humic acid or amino acids, can improve plant tolerance to abiotic stresses like drought, salinity, or extreme temperatures. Chelates can protect plant cells and maintain essential functions under stressful conditions.
  5. Facilitating nutrient transport: Chelates play a key role in transporting essential nutrients from plant roots to other parts of the plant. The stability of chelated compounds allows for efficient nutrient uptake and distribution within the plant.


What is Chelating in Plants?

Chelating in plants refers to the process by which certain organic compounds, known as chelates, form bonds with metal ions and help transport and uptake essential minerals in plant tissues. These compounds act as "chelating agents" by surrounding the metal ions with their chemical structure, creating a stable complex or chelate.

What are Chelates Explained?

Chelates are organic compounds that contain a central atom, typically a metal ion, and form complex structures with other molecules. In the context of plants, chelates play a vital role in the uptake and transport of essential nutrients such as iron, copper, and zinc. They act as "metal-chelating agents" by binding to these nutrients and improving their availability for plant roots to absorb.

How do Chelates Function?

Chelates function by binding to metal ions, forming stable structures that protect the nutrients from undesirable interactions in the soil. This protection is particularly important in soils with unfavorable pH conditions, such as acidic or alkaline soils, where nutrients tend to become less accessible to plants. Chelates enhance the mobility and solubility of minerals, allowing for their efficient uptake through root hairs and transport to various plant cells.

What are Chelated Minerals for Plants?

Chelated minerals for plants, such as chelated iron, are mineral compounds that have been bound to organic chelating agents. These chelates enhance the availability of essential minerals in the soil, making them more easily absorbed by plant roots. Chelated minerals are commonly used in agriculture to address nutrient deficiencies and ensure optimal plant growth and development.


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