MCQ Detailed View

Plants require several essential nutrients for proper growth and development. These nutrients are divided into three main groups based on the quantity in which plants need them:

1. 
   

   Primary nutrients: Nitrogen (N), Phosphorus (P), and Potassium (K) are required in the largest amounts and are often supplemented through fertilizers.

   
   


2. 
   

   Secondary nutrients: Calcium (Ca), Magnesium (Mg), and Sulphur (S) are needed in moderate amounts but are still essential for plant health.

   
   


3. 
   

   Micronutrients: Elements like iron, zinc, manganese, copper, and boron are required in very small quantities.

   
   

In this question, Sulphur (S) is classified as a secondary nutrient. It plays several important roles in plants:

• 
  

  Essential for the synthesis of amino acids (building blocks of proteins).

  
  


• 
  

  Helps in the formation of chlorophyll, which is required for photosynthesis.

  
  


• 
  

  Improves seed production and oil content in crops like mustard and soybean.

  
  


• 
  

  Aids in enzyme activation and vitamin formation.

  
  

The other options are primary nutrients:

• 
  

  Nitrogen (N): Promotes leaf growth and green coloration.

  
  


• 
  

  Phosphorus (P): Supports root development, flowering, and energy transfer.

  
  

Sulphur is absorbed by plants mainly as sulfate ions (SO₄²⁻) from the soil. A deficiency of sulphur can lead to yellowing of young leaves (chlorosis), reduced growth, and poor crop yield.

Thus, among the given options, Sulphur is the correct answer as a secondary plant nutrient, while nitrogen and phosphorus belong to the primary nutrient category.