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Living beings need nutrients for their growth and development. Macronutrients and micronutrients namely carbohydrates, protein, water, vitamins, and minerals. There are different types of micronutrients responsible for various life-essential roles and these micronutrients can be divided into different types of micronutrients as well. A deficiency of micronutrients and abnormally high levels of micronutrients causes problems in both plants and animals.
Key Terms: Nitrification, Hydroponics, Denitrification, Mineral ion concentration, Nutrient solution
What are Micronutrients?
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Food provides humans and plants with chemical compounds important for daily life, growth systems, and repair systems. Apart from macronutrients and water, food also provides micronutrients. They are important for healthy growth, metabolism, and development. They also regulate cell function. Since the human body cannot produce these micronutrients, plants and animals obtain these by consuming food items.
Micronutrients or trace elements, as the name suggests, form a very small portion of our diets, hence are required in very fewer quantities by both plants and animals. In plants, they are required in less than 10 mmol Kg–1 of dry matter.
Micronutrients
- Micronutrients are also called trace elements.
- Humans and plants are dependent on other sources for these micronutrients.
- Micronutrients include vitamins and minerals that help in the prevention of diseases.
- Micronutrients are equally important as macronutrients for our growth and health but are only required in a small and balanced amount.
- Excess of micronutrients results in micronutrient toxicity and lack of the same results in micronutrient deficiency.
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Difference Between Macronutrients & Micronutrients
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Micronutrients form a big part of everyday food intake. They provide us with the energy to perform essential life functions. It helps in growth, reproduction, and respiration. In plants, they help in the proper functioning of the cell membranes, growth of cells, opening, and closing of stomata, etc. Macronutrients include compounds like nitrogen, phosphorus, calcium, magnesium, potassium, etc.
The key differences between Micronutrients and Macronutrients are tabulated below:
| Categories | Macronutrients | Micronutrients |
|---|---|---|
| Definitions | Macronutrients are the nutrients that are required in large amounts. | Micronutrients are the nutrients which are required in small amounts/traces. |
| Constitutes | It includes carbohydrates, protein, fat, alcohol, water, and fiber. | It includes vitamins and minerals. |
| Functions | It provides plants and animals with energy needed for the metabolic system. | It helps in body growth and prevents diseases. |
| Sources | Cereals, legumes, meat, fish, nuts, oils, seeds, etc. | Mainly vegetables, fruits, eggs, green leafy vegetables, fermented foods, etc. |
| Nutrients | N, K, Ca, Mg, P, and S. | Cl, Fe, B, Mn, Zn, Cu, Mo, and Ni. |
As mentioned above, macronutrients are required in greater quantities while micronutrients are required in smaller quantities. Nitrogen, potassium, magnesium, phosphorus, and sulphur are important macronutrients. Examples of micronutrients are chlorine, iron, boron, zinc, copper, molybdenum, nickel, etc.
Also, in plants micronutrients are essentially absorbed from the soil while macronutrients may or may not be absorbed from the soil by roots. Macronutrients help with the formation of carbon compounds and energy storage while micronutrients act as cofactors for enzymes and help in electron transfer.
Types of Micronutrients
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Micronutrients can be divided into four types:
- Water-soluble Vitamins
- Fat-soluble Vitamins
- Macrominerals
- Trace Minerals
Types Of Micronutrients
Water Soluble Vitamins
Water-soluble vitamins can be easily absorbed into tissues and cells of animals and plants for immediate use. They exist in a free state and act as activators of coenzymes. Activation of these coenzymes helps in the formation of certain proteins and fats that help in the production of energy in the human body. Excess of these types of vitamins is passed out in the urine. They are not stored in the body. Water soluble vitamins are regularly replenished in the body through good food and proper diets.
Water-soluble vitamins are directly absorbed into the blood and travel freely. They are circulated freely in water-filled parts of the body. The excess of these vitamins is detected by the kidney and excreted via urine. When reached toxic levels, excess water-soluble vitamins cause a number of diseases.
Major kinds of water-soluble vitamins are Vitamin B-Complex and Vitamin C. Major sources of Water Soluble Vitamins are fresh fruits like citrus fruit and berries, tomatoes, and bell pepper, and fermented foods like yogurt, etc.
Fat-Soluble Vitamins
Vitamins that are not dissolved in water and stored in the liver and fatty tissues for future use are called fat-soluble vitamins. These vitamins play a major role in proper functioning of our immune system, and body growth and help in protection of cells from damage.
- Fat-soluble vitamins are first absorbed into lymph and then get absorbed into bloodstream.
- These vitamins need protein carriers to travel.
- Vitamins are stored in the cells that have fat. They cannot be excreted easily and have a tendency to get stored in fatty tissues of the body.
- Fat-soluble vitamins are Vitamin A, Vitamin D, Vitamin E and Vitamin K.
- The major sources of fat-soluble vitamins are carrots, milk, fish, cheese, soybeans, green leafy vegetables, cereals, vegetables, etc.
Macrominerals
Macrominerals are the minerals required by humans and plants in larger dosages than trace minerals. They help in various functions like muscle function, cell functions, regulation of blood pressure, production of digestive juices, etc. The important macronutrients are calcium, phosphorus, magnesium, sodium, potassium, chloride, and sulphur.
| Macrominerals | Functions |
|---|---|
| Calcium | Necessary for bones and teeth and helps in muscle formation and blood vessel contraction and dilation. |
| Phosphorus | Necessary for bones and helps in cell membrane structure and functions |
| Magnesium | Energy production, important for cell membranes and chromosomes. |
| Sodium | Helps in maintaining the cell wall structure and maintains blood volume and blood pressure |
| Potassium | Acts as a cofactor and facilitates the regulation and activities of enzymes. |
| Chloride | Important factor in nerve impulse transmission |
| Sulphur | Forms amino acids that are important for body proteins and every other cell of the body. |
Trace Minerals
Minerals required in a very small amount than macrominerals are called trace minerals. The major trace minerals are iron, manganese, copper, zinc, iodine, fluoride, and selenium.
Trace minerals perform and aid in various functions like carrying oxygen, bone development, healing, normal brain, and nervous system functions, etc.
| Trace Minerals | Functions |
|---|---|
| Iron | Helps in carrying oxygen from red blood cells to the tissues. |
| Manganese | Acts as an enzyme in metabolism, wound healing, and bone structure development. |
| Copper | Production energy in body and formation of connective tissues. |
| Zinc | Involved in neurological, reproduction, and immune systems. |
| Iodine | Regulation of thyroid gland. |
| Fluoride | Strengthens enamel and balances minerals in bone. |
| Selenium | Involved in metabolic functions. |
Micronutrients in Plants
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Micronutrients are essential to the growth and development functions of plants. Micronutrients may be needed in trace amounts in the plants but they happen to play a very imperative role in their functions and without these the plant productivity would be endangered.
Plants produce their own foods but for these trace minerals, they are dependent on soil and absorb most of the micronutrients through their roots. Micronutrients in plants help in functions like permeability of cells, metabolic processes, maintenance of osmotic concentration of cell sap, and help in various enzyme-related activities, etc. micronutrients play major roles as an aid in Nitrogen Fixation in legumes.
Micronutrients’ role in Nitrogen Fixation
Nitrogen is present in abundance in the atmosphere however, the divalent molecule of nitrogen N2 is too strong a triple bond shared between its atoms. Nitrogen fixation in the root nodules of leguminous plants by rhizobium helps plants to break down nitrogen for its use. There is an interaction between macronutrients and micronutrients to facilitate this cycle.
- Boron is required for nodules growth and nitrogen fixation.
- Molybdenum is involved in nitrogen fixation (conversion of N2 to NH4+) and nitrification (conversion of NH4+ to NO3-).
- The enzyme Nitrogenase is a molybdenum and iron protein.
- The legumes which have a symbiotic relationship with nitrogen-fixing bacteria have a high demand for iron in the form of leghemoglobin.
The important micronutrients for plants are: boron, chlorine, copper, iron, manganese, molybdenum, zinc and nickel. Their respective functions are as follows:
| Micronutrients | Functions in Plants |
|---|---|
| B | Essential for transportation of sugar, cell division and elongation and amino acid production, water splitting reaction. |
| Cl | Photosynthesis reaction and preventions of diseases |
| Cu | Part of enzymes that helps in photosynthesis |
| Fe | Important component of chlorophyll synthesis and photosynthesis |
| Mo | Essential in nitrogen fixation |
| Mn | Helps in chloroplast production and activates enzymes |
| Zn | Important components of many enzymes, helps in balancing plant hormones and auxin activity |
Toxicity And Deficiency Of Micronutrients In Plants
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Excess, as well as deficiency of micronutrients in plants, lead to various diseases and growth issues. A moderate decrease in these micronutrients results in major deficiency and a moderate increase in their levels result in toxicities.
| Micronutrients (Trace Minerals) | Symptoms Of Deficiency | Symptoms Of Toxicity |
|---|---|---|
| Boron | Abnormal growth of shoot system in the sides. And extremely green newer foliage. | Chlorosis in young leaves and later becomes reddish brown |
| Chlorine | chlorosis and spotting in leaves, browning of leaf edges | Size and number of leaves decreases followed by yellow discoloration in them |
| Copper | Seed production hindered | Chlorosis in young leaves and wilting |
| Iron | Hindered growth and leaves turn yellowish, pale green or whitish. | Bronze coloured stippling in leaves |
| Molybdenum | Discolouration of leaves. Yellowish on the margin and pale green at the centre. | Leaves have golden brown and blue tints |
| Manganese | Poor growth of root and shoot systems. Plants will be tiny in size. | Chlorosis of leaves and purple or brown spots in legume leaves |
| Zinc | New leaves are pale, yellow, and spotty, and hence development of the shoot system is hindered. | Mild chlorosis in internal veins and rolling of leaf margins |
| Nickel | chlorosis of young leaves, reduced leaf size, and less upright leaf growth | Hindered development of root and shoot systems. |
Micronutrients Deficiency In Human
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Deficiency of Micronutrients in humans results in various diseases:
- Iron- Anaemia
- Iodine- Hyperthyroid, hypothyroid, goiter and mental retardation
- Calcium- Osteoporosis, muscle cramp, etc.
- Magnesium- High blood pressure and various heart diseases
- Sodium- Low blood sodium
- Potassium- Constipation, kidney problems, muscle weakness, fatigue, and heart issues.
- Chloride- Lung diseases, Addison Diseases
- Zinc- Various skin and digestion conditions
- Vitamin B- Beriberi, anaemia
- Vitamin C- Scurvy
- Vitamin A- Blindness and impaired vision
- Vitamin D- Osteoporosis
- Vitamin K- Weakened blood clotting and bone health
Things to Remember
- Micronutrients are the nutrients required by both plants and animals in small amounts. They are essential in growth and development and help in day-to-day bodily functions.
- Micronutrients are largely vitamins and minerals.
- They are further classified into four types namely; water-soluble vitamins, fat-soluble vitamins, macrominerals, and trace minerals.
- Micronutrients are sometimes referred to as microminerals.
- Few micronutrients are iron, cobalt, zinc, sodium, molybdenum, boron, zinc, etc.
- Excess and deficiency of these micronutrients results in various diseases and affects growth in both plants and humans.
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Sample Questions
Ques 1. List three essential Boron functions in plants. (3 Marks)
Ans. The three important functions of Boron in plants are as follows:
- Boron is required for the transportation of essential elements like calcium. Calcium helps in maintains the structure of cell wall and cell membrane.
- It also helps in the translocation of carbohydrates (sugar) to various parts of plants. Carbohydrates are the end product of photosynthesis and are needed to be transported to various parts of plants to perform various life functions.
- Boron is also responsible for the water-splitting reaction during photosynthesis which produces hydrogen and oxygen for further use by the redox reaction.
Ques 2. Write short notes on micronutrients and their type. (5 Marks)
Ans. Micronutrients are the nutrients required by both animals and plants for metabolic and physiological processes. Since our bodies are incapable of producing these micronutrients, we are dependent on various food sources for them.
Even when the plants are capable of producing their own food. They are dependent upon their roots to absorb these micronutrients from soil to carry out food-producing processes. Micronutrients mainly consist of vitamins and minerals.
Micronutrients are divided into four types:
- Water soluble vitamins: Water soluble vitamins are the vitamins that are water-soluble and can be very easily absorbed into tissues and cells of animals and plants for immediate use. Water soluble vitamins are Vitamin B complex and Vitamin C.
- Fat-soluble vitamins: Vitamins that are not dissolved in water and stored in liver and fatty tissues for future use are called fat-soluble vitamins. Fat soluble vitamins are vitamins A, D, E, and K.
- Macrominerals: Macrominerals are the minerals required by humans and plants in larger dosages than trace minerals. They help in various functions like muscle function, cell functions, regulation of blood pressure, production of digestive juices, etc. Few of the macrominerals are calcium, phosphorus, sulphur, etc.
- Trace minerals: Minerals required in very small amounts than the macro minerals are called trace minerals. Trace minerals perform and aids in various functions like carrying oxygen, bone development, healing, normal brain, and nervous system functions, etc. example of trace minerals are iron, boron, copper, zinc, iodine, etc.
Ques 3. Name four different deficiency symptoms in the plant. Describe these symptoms and mention the minerals responsible for the respective symptoms. (3 Marks)
Ans: Chlorosis: Chlorosis is the discolouration of leaves caused due to loss of chlorophyll. Leaves turn yellow from green. This symptom can be an indication of deficiency of chlorine, nickel, zinc etc. It’s the most common symptom of mineral deficiency in plants.
Necrosis: Abrupt death of tissues in plants especially in leaf and branch areas is called necrosis. Deficiency of minerals such as calcium, magnesium, copper, and potassium, etc can be responsible for it.
Little leaf disease: Little leaf disease refers to stunted growth in young leaves in growing plants. This symptom is the result of zinc deficiency.
Stunted root and shoot growth: Certain mineral deficiency results in stunted/tiny plants. The minerals responsible for this symptom are zinc, molybdenum, etc.
Ques 4. The color of cauliflower turns brown due to which deficiency? (1 Mark)
Ans: The color of cauliflower turns brown due to boron deficiency.
Ques 5. Which micronutrients are the major components of enzyme nitrogenase? (2 Marks)
Ans. Nitrogenase is the enzyme that catalyses the conversion of atmospheric nitrogen to ammonia in the process of nitrogen fixation. The major components of nitrogenase are iron (Fe) and molybdenum (Mo).
Ques 6. What is the role of molybdenum in nitrogen fixation? (2 Marks)
Ans. Molybdenum forms negatively charged ions called molybdate. In plants, these molybdate ions help in conversion of nitrogen into protein in a process called nitrate reductase in Nitrogen fixation.
Ques 7. List at least four differences between macronutrients and micronutrients. (3 Marks)
Ans. 1. Macronutrients are the nutrients required in large amounts. Micronutrients are required in small amounts/traces.
- It includes carbohydrates, protein, fat, alcohol, water, and fiber. It includes vitamins and minerals.
- Macronutrients plants and animals with the energy needed for the metabolic system. Micronutrient aids in body growth and prevents diseases.
- Cereals, legumes, meat, fish, nuts, oils, seeds, etc. are a few examples of macronutrients and micronutrients mainly include vegetables, fruits, eggs, green leafy vegetables, fermented foods, etc.
Ques 8. What are the major differences between water-soluble and fat-soluble vitamins? (3 Marks)
Ans: a. Water-soluble vitamins directly absorb into the blood whereas the fat-soluble vitamins absorb into the lymph and then absorb into the blood.
- Water-soluble vitamins travel freely whereas fat-soluble ones may need protein carriers to travel.
- Water-soluble vitamins can be easily removed from the body when in excess and fat-soluble vitamins tend to accumulate in fat tissues of the human body.
- Water-soluble vitamins are needed by human bodies in frequent dosages while fat-soluble ones may be needed.
Ques 9. Explain the process of mineral absorption in plants. (2 Marks)
Ans. Plants are dependent on soil for the absorption of various minerals for food production. They absorb the mineral salts from the roots and the area of root elongation. Mineral ions are first absorbed into the outer free space of cell from the soil and then these ions are absorbed into the inner space of the cell which is the cytoplasm and vacuole.
Ques 10. Describe the symptoms of sulphur deficiency in plants. (2 Marks)
Ans. Sulphur deficiency in plants is first seen in the young leaves. Sulphur is responsible for the movement of proteins in the cells and is very important for the process of photosynthesis. When the young leaves show stunted growth, especially in leaves, it indicates that the sulphur is relatively immobile in the plant, hence the symptoms.
Ques 11. What are the criteria for the essentiality of elements? (3 Marks)
- The elements must be highly important in aiding the plant growth development and reproduction processes of the plants.
- The elements must be irreplaceable and specific to their respective process. The lack of the same shows deficiency symptoms which hinder plant growth.
- The element must be directly involved in the metabolic purposes of the plants.
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