Question

The inorganic nutrient most often lacking in crops is

(A) carbon.

(B) nitrogen.

(C) phosphorus.

(D) potassium

Short answer

1. The option “carbon” is false.

2. The option “nitrogen” istrue.

3. The option “phosphorous” is false.

4. The option “potassium” is false.

Step-by-step solution

Plant nutrition

The substances which are required to regulate the structure and functions of the plant are collectively called nutrients. Plants need sunlight, water, and inorganic substances to obtain their energy. The inorganic substances are minerals such as nitrogen, phosphorus, and potassium.

Explanation of option (A)

Plants obtain their carbon from the surrounding environments. As all the heterotrophs liberate carbon dioxide through their respiration, carbon sources are abundant in nature.

Therefore, plants do not lack carbon in their nutrition.

Thus, the given option is false.

Explanation of option (B)

Nitrogen is present in the atmosphere abundantly. However, plants can only use nitrogen when it is in nitrate or ammonia form. The rhizobacteria present in the soil helps to fix the atmospheric nitrogen in the plant roots. Legumes are host plants that exhibit mutualism with rhizobacteria.

Therefore, all the plants do not show mutualism with soil bacteria. When nitrate or ammonia present in soil decreases, plants fail to get enough nitrogen.

Thus, the given option is true.

Explanation of option (C)

Phosphorus is present in the soil, and plants roots can absorb it in its ionic form. The ground also includes organic phosphorus (from dead animals decomposed by bacteria), and roots can absorb them easily.

Therefore, plants usually get enough phosphorus from the soil and do not often show its deficiency.

Thus, the given option is false.

Explanation of option (D)

Plant roots readily absorb potassium in its ionic form. Rotten fruits, leaves, and animals also provide potassium to the soil. The plants have developed potassium channels in their transport system to accumulate enough potassium.

Therefore, as potassium is generally available for plants through soil, they do not lack potassium more often.

Thus, the given option is false.