[Biology Class Notes] on Role of Macronutrients and Micronutrients Pdf for Exam

Plants are living organisms and they also require nutrients like us in order to survive, grow, reproduce, and develop. Macronutrients in plants are nutrients that provide energy to the plants and are required in larger amounts to maintain their development and growth. These are the most important elements required for crops and examples include nitrogen (N), potassium (K), calcium (Ca), phosphorus (P), magnesium (Mg), sulphur (S), oxygen (O), carbon (C), and hydrogen (H). Out of these, the most important ones are nitrogen, phosphorus, and potassium, which directly affect plant growth and actually create various parts of the plant. Also, nitrogen is an important component of chlorophyll that plays a vital role in photosynthesis (food synthesising process). 

Micro nutrients in Plants

In addition to macronutrients, micronutrients are the other category of nutrients that are called trace elements or minerals required in a very small quantity that help in growth or metabolism. Some important micronutrients include boron (B), iron (Fe), chlorine (Cl), manganese (Mn), copper (Cu), zinc (Zn), molybdenum (Mo), and nickel (Ni).

Now we will discuss about all macro and micro elements and their functions in detail further.

Role of Macro and Micronutrients

Macronutrients and micronutrients in plants fall under essential nutrients that support plants for all biochemical needs and without which:

• A plant can’t complete its life cycle.

• Other elements can’t replace a specific function for a plant.

• Plants cannot get full nutrition as each essential nutrient is directly involved in plant nutrition.

Out of all the essential nutrients, about half of the elements are considered as macronutrients and functions of macronutrients are very necessary, for example, carbon is required to form proteins, carbohydrates, nucleic acids, and other compounds or key plant macromolecules.

List of Macronutrients and Micronutrients

All the elements are important for plants, some in larger quantities called macronutrients and some in lesser or minute quantities called micronutrients.

Functions of Macronutrients and Micronutrients

It is good to know the structure and functions of macro and micro nutrients for gaining information about these in a better way and recognize the role of each of them. Let’s know the functions they perform in the plants one by one for macro and micronutrients:

• Macronutrients in Plants and Their Functions

The most important crop nutrients are nitrogen, phosphorus, and potassium that affect plant growth directly and create various parts of plants.

1.  Nitrogen

It is important to plants for:

• Metabolism as it is an important substance and part of amino acids, proteins, and enzymes.

• Influences germination and vegetative growth.

• Being a component of chlorophyll, it plays an important role in photosynthesis.

• Responsible for the rapid growth of foliage.

• Provides green colour to the plants.

Deficiency of iron in plants results in stunted crop growth, chlorosis or yellowing of leaves, and weakness during fruiting and flowering, leading to lower yields.

Too much nitrogen is also not good for plants as it causes dark green colouring of leaves, lush growth, crop lodging, and fruit quality reduction.

2. Phosphorus

It is important to plants for:

• Development of roots.

• Maintaining a good quality of flowering, fruiting, and seed production.

• Storing and transporting energy.

• Resistance to disease.

Deficiency of phosphorus leads to stunted plant growth, weakened roots, thin shoots, and dark green/purple/red leaves. Excessive amounts of phosphorus can cause lower reception and deficiency of other elements like Zn, Fe, Cu, Mn, and B.

3. Potassium (K)

It is important to plants for:

• Influencing water uptake.

• Improving drought tolerance.

• Improvement in cold hardiness.

• Providing resistance to fungal diseases and insect pests.

• Synthesizing proteins, sugar, and fat.

Deficiency of potassium in plants leads to growth reduction, burning or yellowing of the leaf margins, and dead spots on older leaves. Excess amounts are also not so beneficial as they affect the uptake of other nutrients including magnesium, calcium, and nitrogen.

Boron, iron, manganese, and zinc are the most important micronutrients in a plant organism. Let’s find out :

1. Boron

It is important for:

Boron deficiency in plants can show various symptoms that include stunted growth of young crops, deformation of leaves, death of growing points, dark brown lesions on leaves, poor flowering, and chlorosis or yellowing of leaves. It should be ensured that boron application should be before the flowering stage in crops, applying later is not beneficial. 

2. Iron (Fe)

Iron is important for:

Deficiency in iron in plants harms younger leaves as it causes yellowing between the veins.

3. Manganese (Mn)

It is important to plants for:

• Influences chloroplast production.

• Actively participating in photosynthetic process.

• Activation of enzymes and influencing germination plus crop maturity.

Deficiency in Mn also may lead to yellowing of veins in the younger leaves called chlorosis.

4. Zinc

It is important to plants for:

• Early growth stages.

• Development of root, seed, and fruit.

• In the process of photosynthesis.

• Balancing plant hormones.

• Activity of auxins.

Deficiency of Zinc results in stunted growth, length reduction of internodes, smaller young leaves, and yellowing on the lower leaves.