Macronutrients in Plants: Role and Functions

Role of Nutrients in Plant Growth

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Mineral nutrition refers to the naturally occurring inorganic nutrients found deep beneath the soil surface. In plant cells, nutrients serve a variety of roles and participate in a variety of metabolic processes. It comprises osmotic pressure regulation, membrane permeability, enzymatic activity, maintaining cell-sap concentration, the electron transport system, buffering action, and many other factors. Nutrients are also classified as follows:

• Micro-nutrients
• Macronutrients

 Let's take a closer look at each of the nutrient kinds discussed under Mineral Nutrition.

Micronutrients

Micronutrients are elements present in small levels, often less than 10 mmoles per kilogram of dry matter. Micronutrients include iron, manganese, copper, molybdenum, zinc, copper, boron, chlorine, and nickel. Trace or micronutrients are nutrients that are required in small levels. It contains the following items:

• Plant tissues absorb copper in the form of Cu²⁺ ions. The component is necessary for plants' overall metabolic processes. Furthermore, the element aids in carbohydrate-nitrogen balance.
• Zinc is absorbed by plants in the form of Zn²⁺ ions. Zinc aids in the production of tryptophan, phosphorus metabolism, and carbohydrates.
• Manganese is required for the processes of photosynthesis, nitrogen metabolism, and respiration. The mineral is necessary for chlorophyll production and acts as a nitrogen metabolism activator.
• Chlorine is usually absorbed in the form of Cl – ions by plants. The element aids in determining the solute concentration and is required for the photosynthetic reaction's water splitting.
• The plants obtain boron as BO₃^3- or B₄O₇^2- . Boron is used in membrane functioning, cell differentiation, pollen germination, glucose transfer, and many other processes.
• Ferric ions (Fe +3) are the form of iron that is absorbed. The micronutrient iron is the one that is needed the most. Iron is a key component of proteins that participate in the electron transport chain. Chlorophyll is formed in part with the help of iron.
• Molybdenum is absorbed as molybdate ions (MoO ²²⁺) in the body. Nitrogenase and nitrate reductase are two enzymes that contain molybdenum.

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Macronutrients

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Macronutrients are elements that are found in enormous levels in plant tissues. They exceed 10 moles per kilogram of dry materials. The macronutrients are carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur, potassium, calcium, and magnesium.

The element is essential for average growth and reproduction to take place. Plants cannot finish their life cycle or set seeds if they lack vital nutrients. The key element must be unique and cannot be replaced by another. The element must be involved in metabolism directly. They are of two types:

Primary Macronutrients

Macronutrients are necessary for plant growth and a healthy overall state.

Nitrogen

Nitrogen is important for plant growth as it is used in protein synthesis and energy metabolism. The plant absorbs nitrogen in the form of nitrate, which is essential for plant growth. It is also required for photosynthesis and the creation of chlorophyll. Nitrogen is primarily engaged in the aerial zone, which is the area of the plant that people can see. It encourages cellular division. A nitrogen deficit causes the loss of vigour and colour. Starting at the bottom of the plant, growth slows and leaves fall off.

Potassium

Potassium is involved in water control and the transport of reserve chemicals in plants. It improves photosynthesis, strengthens cell tissue, and promotes nitrate absorption. Potassium also promotes blooming as well as glucose and enzyme synthesis. As a result, the plant's ability to tolerate unfavourable circumstances, such as low temperatures, improvement, and withering, is reduced. As a result, a lack of Potassium makes plants more susceptible to dry spells, frosts, and fungus attacks. Other important nutrients like nitrogen, calcium, and magnesium, become unbalanced as a result. Dark stains form on the leaves when there is a potassium deficiency.

Phosphorus

Phosphorus plays a role in root growth by stimulating it. It encourages flowering in the aerial zone. Although phosphorus is required for plant growth, it is significantly more critical during the flowering stage. Phosphorus is engaged in energy transfer and storage. It also boosts the overall health of the plant and increases its ability to endure severe climatic conditions. Phosphorus is required for the creation of organic compounds and the proper execution of photosynthesis. A lack of phosphorus causes late, ineffective flowering, browning and wrinkling of the leaves and an overall lack of vigour.

Read more: Nodule Formation

Secondary Macronutrients

Secondary macronutrients are also essential, even if they are consumed in smaller amounts than primary macronutrients. Examples: Calcium, Sulphur, and Magnesium.

Magnesium

Magnesium is required for photosynthesis since it is the core of the chlorophyll molecule. As a result, it is a necessary component for plant growth. Phosphorus absorption and transportation are aided by magnesium. It aids in the storage of sugars inside the plant. Magnesium acts as an enzyme activator, activating more enzymes than any other mineral. Magnesium deficiency causes weak stalks, a loss of greenness in the oldest leaves, and the emergence of yellow and brown spots on the leaves' veins, despite the veins remaining green.

Calcium

Calcium binds to the cell walls of plant tissues, stabilizing them and promoting their formation. Calcium is also essential in cell development and growth. It increases plant vitality by stimulating root development and growth. Calcium aids in the retention of minerals in the soil as well as their transfer. It aids in the development of seeds and neutralizes harmful chemicals in plants. Calcium regulates and stabilizes various processes, and a calcium deficiency results in yellow and brown patches on the leaves. It also slows the growth of plants in general.

Sulphur

Chlorophyll is formed with the help of sulphur. It is required for photosynthesis and also plays a role in protein synthesis and tissue development. Sulphur is important in nitrogen metabolism because it promotes nitrogen efficiency. Sulphur also helps plants defend themselves in general. Sulphur deficiency is uncommon, but the plant becomes lighter in colour, resembling a pale green when it occurs.

Read more: Vitamins and Minerals

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Deficiency Symptoms of Essential Elements

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• The critical concentration of an essential element is the level below which plant growth is slowed.
• When the element is present below the critical concentration, it is said to be deficient.
• Plants exhibit distinct morphological changes in the absence of a specific element, known as deficiency symptoms and are diagnostic of particular element deficits.
• The deficiency symptoms differ from element to element, but they always go away once the lacking mineral nutrient is given to the plant.
• When elements are generally stationary and are not moved out of the mature organs, deficiency symptoms emerge first in the young tissues.
• Sulphur and calcium, for example, are part of the cell's structural components and hence are difficult to release.
• Chlorosis, necrosis, stunted plant growth, premature fall of leaves and buds, and suppression of cell division are examples of deficient symptoms seen in plants.
• Chlorosis is a yellowing of the leaves produced by a lack of chlorophyll due to a lack of the elements N, K, Mg, S, Fe, Mn, Zn, and Mo. 
• Necrosis is the loss of tissue, especially leaf tissue, caused by a lack of Ca, Mg, Cu, and K.
• Cell division is inhibited by a lack of or low N, K, S, and Mo levels.
• Some elements, such as N, S, and Mo, can cause flowering to be delayed if their concentration in plants is low.

Read Also: Class 11 Biology Chapter 12 Mineral Nutrition

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Things to Remember

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• Plants are made up of 60 chemical elements, among which 16 elements are essential.
• Micronutrients include iron, manganese, copper, molybdenum, zinc, copper, boron, chlorine, and nickel. 
• The macronutrients are carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur, potassium, calcium, and magnesium.
• Macronutrients are found at enormous levels in plants.
• Macronutrients can be further classified into two types, primary macronutrients and secondary macronutrients.