Question

Micronutrients are needed in very small amounts because

(A) most of them are mobile in the plant.

(B) most serve mainly as cofactors of enzymes.

(C) most are supplied in large enough quantities in seeds.

(D) they play only a minor role in the growth and health of the plant.

Short answer

1. The option “most of them are mobile in the plants” is false.

2. The option “most serve mainly as cofactors of enzymes” is true.

3. The option “most are supplied in large enough quantities in seeds” is false.

4. The option “they play only a major role in the growth and health of the plant” is false.

Step-by-step solution

Nutrients

The essential substances required by the plants are classified as macro and micronutrients. Macronutrients are required in large quantities, such as carbon, oxygen, nitrogen, potassium, calcium, magnesium, and sulfur.

Micronutrients are required in small quantity such as iron, boron, zinc, nickel, and molybdenum.

Explanation of option (A)

Most of the micronutrients are immobile in plants except chlorine and nickel. Macronutrients such as nitrogen, potassium, and sulfur are mobile in plants.

Therefore, micronutrients are immobile and required in tiny amounts from the soil.

Thus, the given option is false.

Explanation of option (B)

The primary purpose of micronutrients is to serve as cofactors of enzymes. For example, molybdenum is required as a cofactor for the enzyme nitrogenase. Iron is necessary for photosynthetic enzymes and the synthesis of chlorophyll.

Therefore, micronutrients activate certain enzymes in the plants and are only required in tiny quantities.

Thus, the given option is true.

Explanation of option (C)

Seeds contain nutrients that are enough for germination. For further growth and development, micronutrients are necessary.

Therefore, the number of nutrients present in the seeds is not utilized in adult plants.

Thus, the given option is false.

Explanation of option (D)

Plants need micronutrients throughout their development and survival, even though they are required in small quantities. The photosynthetic process and many enzyme-mediated activities need micronutrients as cofactors.

Therefore, micronutrients are also necessary for enzymatic reactions.

Thus, the given option is false.