CBSE Class 11 Mineral Nutrition- Essential Mineral Elements

Essential Mineral Elements NCERT Science Class-11: Essential mineral elements play a vital role in the growth and development of plants. Essential Mineral Elements, also known as mineral nutrients, are essential for various biochemical and physiological processes within plants. While carbon, hydrogen, and oxygen are obtained from air and water, mineral elements are obtained from the soil and are crucial for the overall health and productivity of plants.

What are Mineral Elements?

Mineral elements are inorganic compounds that are essential for the growth and development of plants. They are absorbed by plants through the soil and play a crucial role in various physiological processes, including photosynthesis, respiration, and metabolism.

Mineral elements can be divided into two categories: macronutrients and micronutrients. Macronutrients are required in relatively large quantities, while micronutrients are needed in smaller amounts. There are essential macronutrients like nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S), and essential micronutrients like iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), boron (B), molybdenum (Mo), and chlorine (Cl).

Criteria for Essential Minerals in Plants

• Essentiality: The mineral must be required for the normal growth and development of plants.
• Specificity: Each mineral must have a specific function that cannot be substituted by any other mineral.
• Direct involvement: The mineral must be directly involved in plant metabolism or play a structural role in plant tissues.
• Beneficial effect: The absence or deficiency of the mineral should lead to a specific disorder or growth inhibition.
• Universal occurrence: The mineral should be found in all plants or, at least, in a wide range of plant species.

Essential Mineral Elements in Plants

Depending on the quantity, minerals elements are divided into 2 types those are:

Macronutrients

Macronutrients are minerals that are required by plants in large quantities. They include nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. These minerals are involved in the formation of plant tissues, the production of chlorophyll, and the regulation of various metabolic processes. A deficiency in any of these macronutrients can lead to stunted growth, poor yields, and other health issues.

1. Nitrogen (N): Nitrogen is a key component of amino acids, proteins, nucleic acids, and chlorophyll. It plays a vital role in plant growth, photosynthesis, and overall plant metabolism.
2. Phosphorus (P): Phosphorus is essential for energy transfer and storage in the form of ATP (adenosine triphosphate). It is involved in DNA and RNA synthesis, cell division, root development, and flowering.
3. Potassium (K): Potassium regulates water balance in plants, helps in enzyme activation, and plays a role in photosynthesis, protein synthesis, and overall plant growth.
4. Calcium (Ca): Calcium is essential for cell wall structure and stability. It also plays a role in membrane permeability, enzyme activation, and signal transduction.
5. Magnesium (Mg): Magnesium is a central component of chlorophyll molecules, enabling plants to capture light energy during photosynthesis. It is also involved in enzyme activation and the synthesis of nucleic acids.
6. Sulfur (S): Sulfur is a constituent of amino acids, proteins, and vitamins. It is essential for protein synthesis and plays a role in the synthesis of certain compounds involved in plant defense mechanisms.

Micronutrients

Micronutrients are minerals that are required by plants in trace amounts. They include iron, manganese, zinc, copper, boron, molybdenum, and chlorine. These minerals are involved in various physiological processes, such as enzyme activation, hormone synthesis, and chlorophyll production. Although they are needed in small quantities, a deficiency in any of these micronutrients can have a significant impact on plant growth and health.

1. Iron (Fe): Iron is necessary for the synthesis of chlorophyll, which is crucial for photosynthesis. It is involved in electron transfer reactions and enzyme activation.
2. Zinc (Zn): Zinc is a cofactor for numerous enzymes involved in carbohydrate metabolism, protein synthesis, and hormone regulation. It is essential for overall plant growth and development.
3. Manganese (Mn): Manganese participates in photosynthesis, acting as an enzyme activator. It also plays a role in nitrogen metabolism, lipid synthesis, and antioxidant defense systems.
4. Copper (Cu): Copper is a cofactor for enzymes involved in various metabolic processes, including photosynthesis, respiration, lignin synthesis, and antioxidant defense.
5. Boron (B): Boron is involved in cell wall synthesis, carbohydrate metabolism, and pollen germination. It also facilitates the translocation of sugars within the plant.
6. Molybdenum (Mo): Molybdenum is essential for nitrogen fixation in leguminous plants and is involved in enzyme activation and nitrate assimilation.
7. Chlorine (Cl): Chlorine is involved in photosynthesis, acting as an essential component of the water-splitting enzyme in light-dependent reactions. It also plays a role in osmoregulation and stomatal opening.

These minerals are required by plants in varying quantities for their proper growth, development, and overall physiological functions. They serve as structural components, enzymatic cofactors, and regulators of various metabolic processes, enabling plants to carry out essential functions necessary for survival and reproduction.

Absorption of Mineral Elements in Plants

Plants obtain mineral elements through their roots from the soil. The process of absorption involves the uptake of these elements from the soil solution into the root cells. This absorption process is facilitated by various mechanisms, including active transport, passive diffusion, and root interception. The concentration of mineral elements in the soil, as well as the pH and moisture levels, can influence their availability for absorption by plants.

Once inside the root cells, mineral elements are transported to different parts of the plant through the vascular system. This ensures that these elements are distributed evenly and utilized in various tissues and organs. The movement of mineral elements within the plant is regulated by both passive and active transport mechanisms, ensuring their proper distribution for growth and function.

Active absorption is the process by which plants actively take up minerals from the soil against a concentration gradient. It requires energy in the form of ATP (adenosine triphosphate). Active absorption primarily occurs in the root hairs of plants. This process involves the uptake of minerals through specific carrier proteins or ion channels in the root cell membrane.

Passive absorption, on the other hand, is the process by which minerals are taken up by plants along with water through passive mechanisms. It occurs when the concentration of minerals in the soil solution is higher than that in the root cells. Passive absorption is mainly driven by osmosis and occurs through the non-selective channels or pores present in the root cell membrane.

Functions of Mineral Elements

Mineral elements have several functions in plant growth and development. Some of these functions include:

1. Formation of Plant Body: Mineral elements are essential for the formation of plant tissues, including roots, stems, and leaves.
2. Regulation of Acidity: Mineral elements play a crucial role in regulating the pH balance of the soil. They act as buffers, preventing the soil from becoming too acidic or alkaline.
3. Toxic Effect: While mineral elements are essential for plant growth, they can also have toxic effects if present in excessive amounts. For example, an excess of nitrogen can lead to leaf burn and stunted growth.
4. Enzyme Activation: Mineral elements are involved in the activation of various enzymes that are essential for plant metabolism.
5. Chlorophyll Production: Mineral elements, particularly macronutrients, are involved in the production of chlorophyll, which is essential for photosynthesis.

FAQs on Essential Mineral Elements

Q1: Why are macronutrients required in larger quantities compared to micronutrients in plants?

Answer: 

Macronutrients play essential roles in plant growth, such as forming structural components and regulating physiological processes. Therefore, they are needed in larger quantities, while micronutrients are required in smaller amounts for specific enzymatic functions.

Q2: Explain the importance of nitrogen in plant growth and development.

Answer: 

Nitrogen is a vital macronutrient that is crucial for the synthesis of proteins, nucleic acids, and chlorophyll. It promotes overall plant growth, leaf development, and photosynthesis. Nitrogen deficiency leads to stunted growth and yellowing of leaves. 

Q3: How does phosphorus contribute to energy transfer in plants?

Answer: 

Phosphorus plays a key role in the formation and transfer of energy-rich compounds such as ATP (adenosine triphosphate) in plants. ATP serves as the energy currency for various metabolic reactions, including cellular respiration and photosynthesis.

Q4: How does boron influence plant reproduction? Provide examples.

Answer: 

Boron is involved in pollen germination and pollen tube elongation, which are crucial processes for successful plant reproduction. Boron deficiency can result in poor fruit sets and malformed seeds, impacting crop yield.