8.1 Nutrition in Plants

Short Introduction Any substance that provides necessary elements to the organism for growth and metabolism is called a nutrient. In general, a nutrient may be organic or inorganic; however, plant nutrients are inorganic. The term nutrition is applied to all the processes that are involved in the utilization of nutrients in growth or various metabolic activities of the body. Plants are autotrophs as they obtain inorganic nutrients such as water, carbon dioxide, and certain minerals from the environment and convert them into organic compounds.

Main Idea

Plants are autotrophs that obtain inorganic nutrients from the environment and convert them into organic compounds. Sixteen elements are essential for plant growth: nine macronutrients (required in large quantities) and seven micronutrients (required in trace amounts). Among these, nitrogen is crucial for protein synthesis, and magnesium is essential for chlorophyll formation. Deficiency of either can lead to chlorosis (yellowing of leaves).

Core Concept

Definition of Nutrient and Nutrition Nutrient: Any substance that provides necessary elements to the organism for growth and metabolism is called a nutrient. generated by DeepSeek to PDF

A nutrient may be organic or inorganic; however, plant nutrients are inorganic. Nutrition: The term nutrition is applied to all the processes that are involved in the utilization of nutrients in growth or various metabolic activities of the body. Plants are autotrophs as they obtain inorganic nutrients (water, carbon dioxide, certain minerals) from the environment and convert them into organic compounds. Types of Plant Nutrients Sixteen elements have been found essential for plant growth. They are divided into two categories based on the quantities required: 1. Macronutrients: Required in fairly large quantities (greater than 0.05% dry weight). Nine macronutrients: Carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, sulphur, calcium, and magnesium. 2. Micronutrients: Needed in traces or small amounts (less than 0.05% dry weight) for normal plant growth and development. Seven micronutrients: Iron, boron, manganese, copper, molybdenum, chlorine, and zinc. (Note: The text states that each mineral nutrient is very important for normal plant growth, but it specifically discusses the importance of only nitrogen and magnesium in this section. The role of the rest will be discussed in Biology Grade 11.) Importance of Nitrogen in Protein Synthesis Nitrogen is a macronutrient mainly absorbed by the plant from soil through roots in the form of inorganic nitrogenous compounds like nitrates (NO₃⁻). The major source of nitrates in the soil is the decomposition of dead organic matter. In nitrogen- depleted soils, it can be added as nitrogen fertilizers. In the plant body, these nitrogenous compounds are used to make amino acids, nucleotides, and chlorophyll. Amino acids are then utilized in protein synthesis. Protein is the most abundant organic constituent of the plant body; therefore, nitrogen deficiency can lead to severe growth retardation. The most obvious symptom of nitrogen deficiency is chlorosis (yellowing of plant leaves due to deficiency of minerals), as the deficiency of nitrogen inhibits chlorophyll formation. Importance of Magnesium in Chlorophyll Formation Magnesium is a macronutrient mainly absorbed by the plant from soil through roots in the form of inorganic Mg ions. The major source of magnesium in the soil is the decomposition of dead plant debris. In magnesium- depleted soils, it can be added in the form of dolomitic limestone or magnesium fertilizers like Magnesium sulphate (MgSO₄). In the plant body, magnesium is used to make chlorophyll. Therefore, magnesium deficiency in plants can also lead to chlorosis.

Detailed Explanation

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Plants are autotrophic organisms that synthesize their own food. To do this, they need a supply of essential nutrients, which they obtain from the soil and air. 1. Nutrients and Nutrition: A nutrient is any substance that provides necessary elements for growth and metabolism. Plant nutrients are inorganic. Nutrition is the sum of all processes involved in the utilization of nutrients for growth and metabolism. 2. Macronutrients vs. Micronutrients: Plants require 16 essential elements. These are divided into macronutrients (required in large amounts, >0.05% dry weight) and micronutrients (required in trace amounts, <0.05% dry weight). Macronutrients (9): Carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, sulphur, calcium, magnesium. Micronutrients (7): Iron, boron, manganese, copper, molybdenum, chlorine, zinc. 3. Nitrogen: Nitrogen is a macronutrient absorbed as nitrates (NO₃⁻) from the soil. It is essential for synthesizing amino acids, nucleotides, and chlorophyll. Amino acids are the building blocks of proteins, which are the most abundant organic constituents of plants. Nitrogen deficiency leads to chlorosis (yellowing of leaves) because chlorophyll synthesis is inhibited, and it also causes severe growth retardation. 4. Magnesium: Magnesium is absorbed as Mg²⁺ ions from the soil. It is a central component of the chlorophyll molecule (it is the central atom in the porphyrin ring of chlorophyll). Therefore, magnesium deficiency also leads to chlorosis. 5. Sources of Nitrogen and Magnesium: The major source of both nutrients is the decomposition of dead organic matter (for nitrogen) and dead plant debris (for magnesium). In depleted soils, they can be added as fertilizers (nitrogen fertilizers for nitrogen; dolomitic limestone or magnesium sulphate for magnesium).

Intermediate Level

Plants are autotrophs that require 16 essential elements for growth. These are classified as macronutrients (9 elements: C, H, O, N, P, K, S, Ca, Mg; required in >0.05% dry weight) and micronutrients (7 elements: Fe, B, Mn, Cu, Mo, Cl, Zn; required in <0.05% dry weight). Nitrogen is a macronutrient absorbed as nitrates (NO₃⁻). It is essential for synthesizing amino acids, nucleotides, and chlorophyll. Amino acids are used for protein synthesis, and protein is the most abundant organic constituent of plants. Nitrogen deficiency causes chlorosis (yellowing of leaves) and severe growth retardation. Magnesium is a macronutrient absorbed as Mg²⁺ ions. It is used to make chlorophyll. Magnesium deficiency also causes chlorosis. Both nitrogen and magnesium are obtained from the decomposition of dead organic matter, or added as fertilizers (nitrogen fertilizers; dolomitic limestone or magnesium sulphate) in depleted soils. generated by DeepSeek to PDF

Important Points

• 1. A nutrient is any substance that provides necessary elements to the organism for growth and
• metabolism.
• 2. Plant nutrients are inorganic.
• 3. Nutrition = all processes involved in the utilization of nutrients in growth or metabolic activities.
• 4. Plants are autotrophs; they obtain inorganic nutrients (water, CO₂, minerals) and convert them into
• organic compounds.
• 5. Sixteen (16) elements are essential for plant growth.
• 6. Nine macronutrients (required in large quantities, >0.05% dry weight): Carbon, hydrogen, oxygen,
• nitrogen, phosphorus, potassium, sulphur, calcium, magnesium.
• 7. Seven micronutrients (required in traces, <0.05% dry weight): Iron, boron, manganese, copper,
• molybdenum, chlorine, zinc.
• 8. Nitrogen:
• Absorbed as nitrates (NO₃⁻).
• Used to make amino acids, nucleotides, and chlorophyll.
• Amino acids are used in protein synthesis.
• Nitrogen deficiency causes chlorosis (yellowing of leaves) and severe growth retardation.
• 9. Magnesium:
• Absorbed as Mg ions.
• fertilizers (MgSO₄) in depleted soils.
• Used to make chlorophyll.
• Magnesium deficiency causes chlorosis.

Remember

• Nutrient = substance providing elements for growth/metabolism.
• Plant nutrients = inorganic.
• 16 essential elements: 9 macronutrients + 7 micronutrients.
• Macronutrients (9): C, H, O, N, P, K, S, Ca, Mg.
• Micronutrients (7): Fe, B, Mn, Cu, Mo, Cl, Zn.
• generated by DeepSeek to PDF
• Nitrogen = nitrates → amino acids, nucleotides, chlorophyll → proteins; deficiency → chlorosis + growth
• retardation.
• Magnesium = Mg ions → chlorophyll; deficiency → chlorosis.
• Sources: decomposition of organic matter; fertilizers (nitrogen fertilizers, dolomitic limestone, MgSO₄).

Common Mistakes

• 1. Confusing macronutrients and micronutrients: Macronutrients are required in large amounts (>0.05%
• dry weight); micronutrients are required in trace amounts (<0.05% dry weight).
• 2. Thinking plants absorb nitrogen as N₂ gas: Plants absorb nitrogen mainly as nitrates (NO₃⁻) from the
• soil.
• 3. Forgetting the role of magnesium: Magnesium is the central atom of chlorophyll; without it, chlorophyll
• cannot be formed.
• 4. Thinking chlorosis is only caused by nitrogen deficiency: Chlorosis can be caused by deficiency of
• nitrogen, magnesium, or other minerals (e.g., iron, sulphur).
• 5. Thinking plants are heterotrophs: Plants are autotrophs; they make their own food using inorganic
• nutrients.
• 6. Mixing up the numbers: 9 macronutrients and 7 micronutrients (total 16).

Quick Revision

• Plants are autotrophs that require 16 essential elements for growth. These are classified as nine macronutrients (C,
• H, O, N, P, K, S, Ca, Mg; required in >0.05% dry weight) and seven micronutrients (Fe, B, Mn, Cu, Mo, Cl, Zn; required
• in <0.05% dry weight). Nitrogen is a macronutrient absorbed as nitrates (NO₃⁻); it is used to make amino acids,
• nucleotides, and chlorophyll. Amino acids are used for protein synthesis, and protein is the most abundant organic
• constituent of plants. Nitrogen deficiency causes chlorosis and severe growth retardation. Magnesium is a
• macronutrient absorbed as Mg ions; it is used to make chlorophyll. Magnesium deficiency also causes chlorosis.
• Both nutrients are obtained from the decomposition of dead organic matter, or added as fertilizers in depleted soils.

60-Second Revision

• Nutrient = substance providing elements for growth/metabolism.
• Plant nutrients = inorganic.
• 16 essential elements: 9 macronutrients + 7 micronutrients.
• Macronutrients (9): C, H, O, N, P, K, S, Ca, Mg.
• Micronutrients (7): Fe, B, Mn, Cu, Mo, Cl, Zn.
• generated by DeepSeek to PDF

• Nitrogen = nitrates → amino acids, nucleotides, chlorophyll → proteins; deficiency → chlorosis + growth
• retardation.
• Magnesium = Mg ions → chlorophyll; deficiency → chlorosis.
• Sources: decomposition of organic matter; fertilizers (nitrogen fertilizers, dolomitic limestone, MgSO₄).
• Frequently Asked Questions (FAQs)
• Q1. What is a nutrient? Answer: Any substance that provides necessary elements to the organism for growth and
• metabolism is called a nutrient.
• Q2. What is nutrition? Answer: The term nutrition is applied to all the processes that are involved in the utilization
• of nutrients in growth or various metabolic activities of the body.
• Q3. Why are plants called autotrophs? Answer: Plants are called autotrophs because they obtain inorganic
• nutrients such as water, carbon dioxide, and certain minerals from the environment and convert them into organic
• compounds.
• Q4. How many essential elements are required for plant growth? Answer: Sixteen elements have been found
• essential for plant growth.
• Q5. What are macronutrients and micronutrients? Answer: Macronutrients are elements required in fairly large
• quantities (greater than 0.05% dry weight). There are nine macronutrients: carbon, hydrogen, oxygen, nitrogen,
• phosphorus, potassium, sulphur, calcium, and magnesium. Micronutrients are elements needed in traces or small
• amounts (less than 0.05% dry weight). There are seven micronutrients: iron, boron, manganese, copper,
• molybdenum, chlorine, and zinc.
• Q6. Why is nitrogen important for plants? Answer: Nitrogen is a macronutrient absorbed as nitrates (NO₃⁻) from
• the soil. It is used to make amino acids, nucleotides, and chlorophyll. Amino acids are utilized in protein synthesis.
• Nitrogen deficiency can lead to severe growth retardation and chlorosis (yellowing of leaves).
• Q7. Why is magnesium important for plants? Answer: Magnesium is a macronutrient absorbed as Mg ions from
• the soil. It is used to make chlorophyll. Magnesium deficiency in plants can lead to chlorosis.
• Q8. What is chlorosis? Answer: Chlorosis is the yellowing of plant leaves due to deficiency of minerals. It occurs
• because the deficiency of nitrogen or magnesium inhibits chlorophyll formation.
• Q9. What are the sources of nitrogen and magnesium for plants? Answer: The major source of nitrogen in the
• soil is the decomposition of dead organic matter; in nitrogen-depleted soils, it can be added as nitrogen fertilizers.
• The major source of magnesium in the soil is the decomposition of dead plant debris; in magnesium-depleted soils,
• it can be added as dolomitic limestone or magnesium fertilizers like magnesium sulphate (MgSO₄).
• Q10. Which mineral nutrients are specifically discussed in this section? Answer: The section specifically
• discusses the importance of nitrogen and magnesium. The role of the rest of the plant nutrients will be discussed in
• Biology Grade 11.
• Multiple Choice Questions (MCQs)
• Q1. How many elements are essential for plant growth? A. 9 B. 16 C. 7 D. 12 Correct Answer: B Explanation: Sixteen
• elements have been found essential for plant growth.
• generated by DeepSeek to PDF

• Q2. Which of the following is a macronutrient? A. Iron B. Zinc C. Magnesium D. Copper Correct Answer: C
• Explanation: Magnesium is a macronutrient. Iron, zinc, and copper are micronutrients.
• Q3. Which of the following is a micronutrient? A. Nitrogen B. Phosphorus C. Boron D. Calcium Correct Answer: C
• Explanation: Boron is a micronutrient. Nitrogen, phosphorus, and calcium are macronutrients.
• Q4. How many macronutrients are essential for plant growth? A. 7 B. 9 C. 16 D. 5 Correct Answer: B Explanation:
• There are nine macronutrients.
• Q5. How many micronutrients are essential for plant growth? A. 7 B. 9 C. 16 D. 5 Correct Answer: A Explanation:
• There are seven micronutrients.
• Q6. Nitrogen is mainly absorbed by plants in the form of: A. N₂ gas B. Nitrates (NO₃⁻) C. Ammonia (NH₃) D. Amino
• acids Correct Answer: B Explanation: Nitrogen is mainly absorbed by plants from soil through roots in the form of
• inorganic nitrogenous compounds like nitrates (NO₃⁻).
• Q7. Which of the following is a role of nitrogen in plants? A. Formation of chlorophyll B. Protein synthesis C. Both A
• and B D. Neither A nor B Correct Answer: C Explanation: Nitrogen is used to make amino acids (for protein
• synthesis), nucleotides, and chlorophyll.
• Q8. Magnesium is essential for the formation of: A. Proteins B. Chlorophyll C. Carbohydrates D. Lipids Correct
• Answer: B Explanation: Magnesium is used to make chlorophyll.
• Q9. What is chlorosis? A. Yellowing of leaves B. Wilting of leaves C. Curling of leaves D. Dropping of leaves Correct
• Answer: A Explanation: Chlorosis is the yellowing of plant leaves due to deficiency of minerals.
• Q10. What is the major source of magnesium in the soil? A. Decomposition of dead plant debris B. Nitrogen
• fertilizers C. Dolomitic limestone D. Magnesium sulphate Correct Answer: A Explanation: The major source of
• magnesium in the soil is the decomposition of dead plant debris.
• Subtopic 8.1 complete. Reply "next" to approve and I will produce Subtopic 2: 8.2 Transport in Plants (Need of
• Transport, Structure of Root and Root Hairs, Uptake of Water and Minerals, Transpiration, Translocation).