Plant Nutrients and Their Roles
Plant Nutrients


Mainly there are three essential nutrients Carbon(C), Hydrogen (H), Oxygen(O). These are non-fertilizer elements.


All oxygen available to life earth comes from plants. Plants don’t absorb oxygen from the air, but instead, acquire it during the breakdown of carbon dioxide as part of photosynthesis. Most of the oxygen plants take in is expelled as a byproduct. Only a very small amount is actually used by the plant for respiration. Oxygen interacts with nitrogen in a process called denitrification, and it affects other elements’ oxidation state as well. Only the leaves and stems of a plant acquire oxygen through photosynthesis. The roots of a plant are forced to take in oxygen from the environment through air spaces in the soil.


Carbon is the primary energy source and building block for plant tissues. Crop residues, green manures and animal wastes can be significant sources of organic carbon in the soil. Carbon is converted through photosynthesis into simple sugars; carbon helps plants build starches, carbohydrates, cellulose, lignin and protein. Almost half of a plant’s dry matter contains carbon.


Nearly all organic compounds also contain hydrogen atoms, which explains why plants need the hydrogen they get from water molecules through photosynthesis. Hydrogen is necessary for building sugars and other molecules to produce glucose for plant energy. Hydrogen is rarely a limiting nutrient.

Hydrogen is known as a structural element; hydrogen is present in both the atmosphere and the growing environment. Hydrogen is an element and can be compound as well. As an element, hydrogen is the lightest, with one protein, one electron pair, creating a constant bond, which takes the form of a gas.

Primary (macro) nutrients are nitrogen, phosphorus, and potassium. They are the most frequently required in a crop fertilization program. Also, they need the greatest total quantity of plants as fertilizer.


Nitrogen is a component of vitamins, amino acids and energy systems within the plant, which forms its proteins. Thus, N is directly responsible for increasing protein content in the plant. Nitrogen is necessary for chlorophyll synthesis and, as a part of chlorophyll molecules, is involved in photosynthesis. Lack of N and chlorophyll means the plant will not utilize sunlight as an energy source to carry on essential functions such as nutrient uptake. In addition, Aids in the production and use of carbohydrates, Affect energy reactions in the plant.


The highest levels of P in young plants are found in tissue at the growing point. As crops mature, most P move into seeds, fruit or both. Phosphorus is noted especially for its role in capturing and converting the sun’s energy into useful plant compounds. Under P deficiency, some crops, such as corn, tend to show abnormal discoloration. In addition, Increases water-use efficiency, Hastens maturity. 


Potassium enhances many enzyme actions aiding in photosynthesis and food formation. It builds cellulose and helps translocate sugars and starches. Potassium is vital to producing grains rich in starch. Potassium maintains turgor and reduces water loss and wilting. Potassium is known as the ‘quality nutrient’ because of its important effects on factors such as size, shape, color, taste, shelf life, fiber and other quality-related measurements. In many high yielding crops, the K content in the plant is comparable to the nitrogen content. Potassium maintains turgor and reduces water loss and wilting. Potassium is absorbed by plants in the ironic form, indicated as K+. In addition, it improves the quality of seeds and fruit, Improves winter hardiness, Increases disease resistance.

The secondary nutrients are calcium, magnesium, and sulfur. For most crops, these three are needed in lesser amounts than the primary nutrients. They are growing in importance in crop fertilization programs due to more stringent clean air standards and efforts to improve the environment.


Magnesium is mobile within the plant and moves easily from older to younger tissues. When Mg deficiencies occur, the lower (older) leaves are affected; first, plants require Mg to capture the sun’s energy for growth and production through photosynthesis. The key element of chlorophyll production, Improves utilization and mobility of phosphorus, Activator and component of many plant enzymes, Increases iron utilization in plants, Influences earliness and uniformity of maturity. Magnesium act as a phosphorus carrier in plants and is required for better root formation and thus for better nutrient and water efficiency in plants. In addition, it Increases iron utilization in plants, Influences earliness and uniformity of maturity.


Sulfur is present in several organic compounds that give the characteristic orders to garlic, mustered, and onion. Sulfur is also important in photosynthesis, and for winter crop hardness—sulfur aids in seed production. Sulfur appears in every living cell and is required for the synthesis of certain amino acids (cysteine and methionine) and proteins. However, sulfur isn’t a constituent of chlorophyll. It’s still vital in chlorophyll formation. Leguminous plants need sulfur for efficient nitrogen fixation.

It helps to the synthesis of an integral part of amino acids, helps develop enzymes and vitamins, and promotes nodule formation on legumes.


Calcium helps form the compounds that makeup part of cell walls, which in turn, strengthen the plant structure. Calcium deficiencies occur most often in acidic, sandy soils from which calcium leaches via rain or irrigation water. Calcium builds yields indirectly by improving root growth conditions and stimulating microbial activity: molybdenum availability and uptake of other nutrients. Calcium helps balance organic acids within the plant as well as activates several plant enzyme systems. Calcium stimulates root and leaf development and affects uptake and activity of other nutrients. Calcium helps enable nitrogen-fixing bacteria that form nodules on the roots of leguminous plants to capture atmospheric nitrogen gas and convert it into a form plants can use. 


Boron improves seed under stressful conditions. Although required in small amounts, boron is a component of all cell walls in the plant. Boron deficiencies are more pronounced during drought periods when root activity is restricted. Corn most effectively uses boron when it’s applied through broadcast soil application. The line between deficiency and toxicity is narrow than other essential nutrients. Farmers should apply at the proper rate and with proper addition, it Essential for the germination of pollen grains and growth of pollen tubes; essential for seed and cell wall formation promotes maturity, Necessary for sugar translocation, and Affects nitrogen and carbohydrate.


Chloride supports the transport of nutrients such as calcium, magnesium and potassium within a plant. Chloride is involved in the chemical breakdown of water in the presence of sunlight and activities several enzyme systems. Stromata regulates the release of moisture from plants so they can minimize water loss during stressful dry provides. Chloride is key in stromata regulation. Chlorides play an important role in plants as they acclimate to changing water availability ( or make osmotic adjustment). It interferes with P uptake and enhances the maturity of small grains on some soils.


Manganese is very immobile in plants, so deficiency symptoms appear first on the youngest leaves, with yellowing between the wins. Sometimes a series of brownish-black spots appear. Although manganese deficiencies are often associated with high soil pH, they may result from an imbalance with other nutrients such as calcium (Ca), magnesium (Mg), and iron(Fe). Manganese deficiencies are most common in high organic matter soil and in those soils with naturally low manganese content and neutral to alkaline pH.


Most iron fertilizer sources work best applied as foliar sprays. Iron deficiencies may be caused by an intolerance with other metals copper (Cu), manganese (Mn) and molybdenum (Mo). Iron is a catalyst for chlorophyll formation. Iron act as an oxygen carrier in the nodules of legume roots. Plants deficient in iron will often display a pale green leaf color (chlorosis), with a sharp distinction between green veins and yellow interveinal tissues. In addition, it promotes the formation of chlorophyll, acts as an oxygen carrier, reactions involving cell division and growth.


Nickel is a component of the urease enzyme and is, therefore, necessary for the conversion of urea to ammonia in plant tissue, making it important in [lant nitrogen metabolism. 

Nickel deficiency has been observed in some nursery plants and tree crops. Affected trees develop mouse-ear, a condition marked by small, curled leaves and stunted growth. No nickel deficiencies have been observed under crop growing conditions, but in crop research settings, agricultural scientists have reproduced deficiency symptoms such as chlorosis of young leaves.


Copper is the most immobile of the micronutrients. Copper is necessary to chlorophyll formation in plants and catalyzes several other plant reactions. Organic soils are the most vulnerable to copper deficiency; heavy, clay type soils are least vulnerable. Other metals in the soil, such as iron, manganese, and aluminum, affect the availability of copper for plant growth. In addition, it catalyzes several plant processes, a Major function in photosynthesis, a Major function in reproductive stages, indirect role in chlorophyll production. 


Zinc is less mobile within the plant, so deficiency symptoms first appear on the young leaves. Protein synthesis and growth regulation require zinc. Reduced hormone production due to a zinc-deficient plant will cause the shortening of internodes and stunted leaf growth. As soil pH increases, zinc decreases. Zinc aids synthesis of plant growth substances and enzyme systems and is essential for promoting certain metabolic reactions, which are particularly critical in the early growth stages. In addition, it necessary for starch formation, aids in seed formation, and necessary for carbohydrate formation.


Plants take molybdenum as the MoO42- anions. Excessively molybdenum is toxic, especially to grazing animals. Molybdenum becomes more available as soil pH goes up, the opposite of most other micronutrients. Molybdenum deficiency symptoms show up as a general yellowing and stunting of the plant. A molybdenum deficiency can also cause marginal scorching and cupping or rolling of leaves. It Required to form the enzyme “nitrate reductase,” which reduces nitrates to ammonium in the plant, Aids in the formation of legume nodules, and Needed to convert inorganic phosphates to organic forms in the plant.

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