Question

Which of the following are called primary elements?
(A) Ca, Na, Mg, Fe
(B) C, H, O, N, P
(C) Fe, Mo, Mn, B
(D) Ca, Mg, P, K

Answer 1

Hint: 17 essential elements mandated by plants for regular growth, development, and reproduction. These are either macronutrients, needed in large amounts of micronutrients, expected in small amounts. Macronutrients are of three kinds, primary, secondary and tertiary elements.

Complete answer:
Primary elements are elements that originate from air and water. It comprises carbon, hydrogen and oxygen. Other primary elements are phosphorus, potassium and nitrogen. Secondary and tertiary elements contain sulfur, magnesium and calcium. Plants must attain these essential minerals for their growth and development. The macronutrients are of the following: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sulfur (S), magnesium (Mg), carbon (C), oxygen (O), hydrogen (H). Whereas, micronutrients include iron (Fe), boron (B), chlorine (Cl), manganese (Mn), zinc (Zn), copper (Cu), molybdenum (Mo), nickel (Ni). Micronutrients are also known as trace elements.
i. Ca, Na, Mg, Fe: These are the secondary elements.
ii. Fe, Mo, Mn, B: These are micronutrients. These are present in small quantities in the soil.
Functions of nutrients:
a. They help in the division of plant cells.
b. It helps in the activation of enzymes and helps in maintaining the turgidity of the cell.
c. It is an important constituent of amino acids, coenzymes, and vitamins.
Hence, the correct answer is option B.

Note: Soil is an important source of nutrients desired by plants for growth. The three major nutrients are nitrogen (N), phosphorus (P) and potassium (K). Jointly they make up the trio identified as NPK. Other significant nutrients are calcium, magnesium, and sulfur.