Question

Which of the following elements is not required by plants for their normal healthy growth?
A. Calcium
B. Magnesium
C. Lead
D. Nitrogen

Answer 1

Lead, iodine and sodium are usually not required by the plant for their growth. These are non-essential elements in plant growth. Only a few elements are essential for plant growth and are known as essential elements such as phosphorus, calcium, sulphur, oxygen, nitrogen etc.

Complete answer:
There are two types of elements essential and non essential elements. Essentials elements are those which are required by plants for their growth and development. There are generally seventeen essential elements. Carbon, oxygen, sulphur, potassium, magnesium, nitrogen, calcium, phosphorus, magnesium, zinc, nickel, chlorine, copper and molybdenum are the essential elements which help plants for growing. The primary nutrients are nitrogen, phosphorus and potassium because they are required in large amounts as compared to others. The intermediate nutrients are sulphur, calcium and magnesium as they are required in certain amounts. Oxygen, carbon and hydrogen can be obtained from the atmosphere.
Magnesium is the powerhouse in plants during photosynthesis. It gives green color to leaves as it is present in chlorophyll. Calcium is responsible for providing support to cell walls of plants. It is found in the form of calcium pectate. Nitrogen is the most essential element and is a major component of chlorophyll. Lead, iodine and sulphur are generally not useful for plants and are considered as non essential elements.

So the correct option is C lead because it is a non essential element for growth and development in plants. It can be toxic for plants.

Note: There are seventeen essentials elements used for nutrition in plants. Out of that some are present in the atmosphere. These are categories as macroelements and microelements on the basis of their requirements by plants. Macronutrients are major nutrients such as carbon, oxygen, sulphur, calcium etc. Micro nutrients are trace elements such as copper, zinc, magnesium.