Question

Which one of the following is not a micronutrient?
A. Boron
B. Molybdenum
C. Magnesium
D. Zinc

Answer 1

It occurs in the soil in the form of exchangeable, water soluble, and fixed forms. It is an important portion of the chlorophyll molecule.

Complete Answer:
Micronutrients are nutrients that the body uses in smaller quantities for its growth and development. In plants, seven essential micronutrients occur. The permeability of a cell membrane is controlled by some nutrients, and some others regulate buffer action, osmotic pressure, etc.
Now, let us find the solution from the options-
- Boron is a micronutrient present in tourmaline, a highly insoluble mineral that is necessary for the cell wall to be properly formed and reinforced. In flowering, cell division, fruiting, and pollen germination, Boron plays a key role. Boron deficiency results in decreased production of seeds and grains. Therefore, the option A is incorrect.

- Molybdenum is also a micronutrient which is essential for the formation of pollen. It is responsible for the fixation of nitrogen as well. The signs of Molybdenum deficiency are decreased fruit or grain growth. Therefore, the option B is incorrect.

- Magnesium is known to be abundantly present in soil as magnesium silicate, an unavailable form that, after weathering, becomes accessible to plants. It is an exchangeable action. As one of the macronutrients for plants, magnesium is essential. It plays an essential part in the metabolism of photosynthesis and carbohydrates. It is an important portion of the chlorophyll molecule. Magnesium for the activation of several essential enzymes is needed by roots and micro-organisms that lack chlorophyll. On mature leaves, magnesium deficiency caused massive interveinal chlorosis and necrotic or purple spots.

- Zinc is also a micronutrient which is an important component that assists in photosynthesis, production of energy and growth control. Zinc deficiency may result in slower maturity and a decrease in leaf size. Therefore, the option D is incorrect.

Thus, the correct answer is option (C) Magnesium.

Note: In plant cells, the micronutrient concentration is below 1 mg/g/ dry weight. Every micronutrient is absorbed by the roots. If there is abundance in the cell above the necessary level, micronutrients are toxic.