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.

Verified step by step guidance

1. Identify the role of micronutrients in plants: Micronutrients, despite being required in small amounts, are essential for various physiological functions in plants.
2. Understand the concept of cofactors: Micronutrients often serve as cofactors for enzymes. Cofactors are non-protein chemical compounds that are required for the biological activity of proteins, especially enzymes.
3. Evaluate the options in relation to cofactors: Since many micronutrients act as cofactors helping in catalytic functions of enzymes, their primary role is not just limited to mobility within the plant or being stored in seeds in large quantities.
4. Eliminate other options: Options 'a', 'c', and 'd' can be eliminated as they either misrepresent the role of micronutrients or provide less accurate reasons for why only small amounts are needed.
5. Choose the correct answer: The best choice is 'b. most serve mainly as cofactors of enzymes.' because it accurately reflects the critical and specific roles micronutrients play in plant physiology, even in small amounts.

Key Concepts

Micronutrients

Micronutrients are essential elements required by plants in trace amounts for various physiological functions. Unlike macronutrients, which are needed in larger quantities, micronutrients such as iron, zinc, and copper play critical roles in enzyme function, photosynthesis, and overall plant health. Their deficiency can lead to significant growth and developmental issues.

Cofactors of Enzymes

Cofactors are non-protein chemical compounds that assist enzymes in catalyzing biochemical reactions. Many micronutrients act as cofactors, meaning they are necessary for the proper functioning of enzymes that facilitate vital processes like metabolism and nutrient assimilation in plants. Without these cofactors, enzyme activity can be severely impaired.

Plant Mobility of Nutrients

The mobility of nutrients in plants refers to their ability to move from one part of the plant to another, particularly from older tissues to younger ones. Micronutrients are often less mobile than macronutrients, which means deficiencies can manifest in younger leaves first. Understanding nutrient mobility is crucial for diagnosing nutrient deficiencies and managing plant health effectively.