Problem 91 - Objective Biology for NEET

Question

Function of zinc is (a) Synthesis of chlorophyll (b) Biosynthesis of IAA (c) Closing of stomata (d) Oxidation of carbohydrate

Step-by-Step Solution

Answer

The correct answer is (a) Synthesis of chlorophyll. As the synthesis of chlorophyll is the key function zinc serves in plants.

Step 1: Understand the Role of Zinc in Plants

Zinc is an essential mineral nutrient for plants. It is involved in many physiological and biochemical functions and is necessary for the production of chlorophyll and certain enzymes.

Step 2: Evaluate the given Options

In the context of these functions, Option (a) states that Zinc is needed for synthesis of chlorophyll. This seems to align well with the established role of Zinc. Now, let's look at the other options.

Step 3: Analysis of other options

Option (b) is about Biosynthesis of IAA (Indole Acetic Acid), a plant hormone that in general, is not directly linked with Zinc. Option (c) refers to the closing of stomata, which is generally regulated by light, carbon dioxide concentration, and the hormone abscisic acid, not directly zinc's function. Option (d) is about the Oxidation of carbohydrates, which is a metabolic process without a direct link to Zinc. After evaluating all the options, the function which directly relates to Zinc is the synthesis of chlorophyll, so the correct choice is Option (a).

Step 4: Select the Correct Answer

Based on the evaluations made in previous steps, the most appropriate answer is Option (a), which accurately describes the function of Zinc in plants, that is, Zinc is required in the synthesis of chlorophyll. The other options, while valid functions in plant biology, are not directly related to zinc's role.

Key Concepts

Zinc Function in Plants

Zinc is a vital micronutrient for plants, playing a critical role in their growth and development. Although plants require it in smaller amounts compared to macronutrients, its influence is significant. Zinc functions primarily as an enzyme cofactor aiding in various metabolic activities, including protein synthesis and hormone regulation.

Important roles of zinc in plants include:

• Enzyme activation: Zinc activates various enzymes that drive essential chemical reactions within plant cells.
• Protein synthesis: It contributes to the translation of genetic code into proteins, a critical component for plant structure and function.
• Hormone regulation: Zinc is involved in the synthesis of auxin, a crucial plant hormone that assists in growth regulation.

Zinc facilitates resistance to plant diseases and stress, showcasing its necessity for healthy plant life. A deficiency in zinc can lead to poor growth and reduced crop yields.

Chlorophyll Synthesis

Chlorophyll is the green pigment central to the process of photosynthesis in plants. It's critical because it helps capture light energy, which is then converted into chemical energy for plant growth. Chlorophyll synthesis, however, is a complex process reliant on various nutrients and factors, with zinc being one of them.

During the synthesis of chlorophyll, zinc acts as a supporting element. It helps in the stabilization of chlorophyll molecules and overall protein structure. This aids not only in the production but also in the retention of chlorophyll, which is necessary for the photosynthetic process.
A shortage of zinc can result in chlorosis, a condition where leaves lose their green color, showing patches of yellow across their surface due to reduced formation of chlorophyll. Thus, zinc is necessary to sustain healthy, green foliage.

Plant Hormones

Plant hormones, also known as phytohormones, are chemicals that regulate plant growth, development, and responses to environmental stimuli. They play a significant role in orchestrating plant activities from seed germination, flower development to leaf shedding.

Some common plant hormones and their functions include:

• Auxins: Promote stem elongation and are crucial in regulating growth.
• Gibberellins: Help in seed germination, breaking seed dormancy.
• Abscisic Acid (ABA): Moderates stomatal closure and stress responses.
• Cytokinins: Stimulate cell division and growth.

Zinc's involvement in plant hormone mechanisms includes aiding in auxin production. While it doesn't directly synthesize all hormones, zinc's influence in balancing hormone levels is crucial for plant homeostasis and adaptation to changes.

Stomatal Regulation

Stomata are tiny openings on plant leaves and stems that manage gas exchange, allowing carbon dioxide in and oxygen out. They also regulate water vapor loss through a process known as transpiration. Stomatal regulation is vital for maintaining plant hydration and photosynthesis.

Several factors influence stomatal regulation:

• Light: Stomata generally open with light to allow in carbon dioxide for photosynthesis.
• Water levels: Can affect how wide stomata open or close, as plants conserve water in dry conditions by closing stomata.
• Hormones: Abscisic acid (ABA) plays a key role in closing stomata under stressful conditions like drought.

Zinc, while not directly responsible for stomatal opening or closing, contributes to the overall health and metabolic functions of the plant, indirectly supporting the stomatal activity. Proper zinc levels help ensure the plant is strong enough to efficiently manage stomatal regulation.