Problem 6 - Campbell Biology

Question

A mineral deficiency is likely to affect older leaves more than younger leaves if (A) the mineral is a micronutrient. (B) the mineral is very mobile within the plant. (C) the mineral is required for chlorophyll synthesis. (D) the mineral is a macronutrient.

Step-by-Step Solution

Answer

The correct answer is (B).

Step 1: Identify Key Information

The problem states that a mineral deficiency is likely to affect older leaves more than younger leaves.

Step 2: Understand Mineral Mobility

If a mineral is very mobile within a plant, the plant can move it from older leaves to younger leaves when there's a deficiency. This means older leaves will show deficiency symptoms first.

Step 3: Analyze Each Option

Evaluate the given options: (A) Micronutrient: This does not necessarily imply mobility.(B) Very mobile within the plant: Fits the understanding from Step 2.(C) Required for chlorophyll synthesis: Does not address mobility.(D) Macronutrient: Like micronutrient, this does not imply mobility.

Step 4: Select The Best Answer

Since mobility of the mineral is key to older leaves showing deficiency first, option (B) is the correct answer.

Key Concepts

mineral mobility in plants

Mineral mobility in plants is important in understanding how nutrients move and where deficiencies show symptoms. When a plant faces a deficiency, it can relocate mobile minerals from older leaves to newer leaves. This ensures the growth of new tissues.
For example, nitrogen is a mobile nutrient. If the plant experiences a nitrogen deficiency, it will transfer nitrogen from the older leaves to the younger ones. As a result, older leaves show symptoms first, such as yellowing or chlorosis.
On the other hand, immobile minerals remain in the tissue where they were originally deposited. Calcium is an immobile nutrient, meaning any deficiency will appear at the growing points like the young leaves or fruits.
Understanding mineral mobility is crucial for diagnosing nutrient deficiencies and ensuring proper plant nutrition. Key points to remember:

• Mobile minerals move to newer tissues, causing older leaves to show deficiency symptoms first.
• Immobile minerals stay in place, affecting young growth areas during deficiency.

micronutrients vs macronutrients

Plants require a variety of nutrients for healthy growth. These nutrients are categorized into micronutrients and macronutrients based on the amount needed.
Micronutrients are needed in smaller quantities but are still vital for plant function. Examples include iron, manganese, zinc, copper, molybdenum, boron, chlorine, and nickel. Despite their small quantities, a deficiency in any micronutrient can severely impact plant health.
Macronutrients, in contrast, are required in larger quantities. They include nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. These nutrients are fundamental building blocks for plant structures and key metabolic processes.
Differences between Micronutrients and Macronutrients:

• Amount Needed: Micronutrients are needed in trace amounts, while macronutrients are needed in larger amounts.
• Function: Both are essential, but macronutrients often play larger roles in structural and energy-related processes.
• Deficiency Symptoms: Deficiencies in macronutrients typically show more pronounced deficits as they are used in greater quantities.

Ensuring balanced nutrition with both micro and macro elements is crucial for optimal plant health.

chlorophyll synthesis

Chlorophyll is the green pigment essential for photosynthesis, allowing plants to convert light energy into chemical energy. Several key nutrients are required for chlorophyll synthesis, including nitrogen, magnesium, and iron.
Nitrogen is a fundamental component of chlorophyll. Without sufficient nitrogen, plants cannot produce enough chlorophyll, leading to yellowing leaves, a condition known as chlorosis.
Magnesium sits at the center of the chlorophyll molecule. Thus, a magnesium deficiency directly impacts chlorophyll production, causing interveinal chlorosis where leaves turn yellow while veins remain green.
Iron is another crucial element for synthesizing chlorophyll. It functions indirectly by assisting in photosynthesis-related enzymes. Lack of iron leads to young leaves turning yellow, a condition termed iron chlorosis.
Key Nutrients for Chlorophyll Synthesis:

• Nitrogen: Vital for building the chlorophyll molecule.
• Magnesium: Central atom in chlorophyll, critical for its structure.
• Iron: Essential for enzyme function in chlorophyll production.

Proper nutrient management is necessary to ensure plants have the resources to maintain healthy chlorophyll levels and carry out photosynthesis efficiently.