Plant Nutrition Questions and Answers

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Plant nutrition is a vital topic in O Level Biology, focusing on how plants obtain and use nutrients for growth and survival. Understanding the types of nutrients, their functions, and deficiency symptoms is crucial for exam preparation. This guide provides clear explanations, practical examples, and exam tips to help you score higher marks.

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Topic Overview

Plant nutrition involves studying essential minerals and nutrients required by plants to grow, produce chlorophyll, and reproduce. Macro-nutrients such as nitrogen, phosphorus, and potassium are absorbed from the soil, while micro-nutrients like magnesium and iron are also necessary in small amounts. This topic also covers the deficiency symptoms and the role of each nutrient, which is important for both exams and practical applications.

 Diagram showing plant nutrition essentials

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Exam Questions and Answers

Question 1

Question:
What is the role of nitrogen in plant nutrition?

Answer:
Nitrogen is essential for making proteins and chlorophyll.

Explanation:
Nitrogen supports leaf growth and photosynthesis. Deficiency causes yellowing leaves (chlorosis).

Exam Tip:
Remember: “Nitrogen = N for leaves”

Question 2

Question:
Why do plants need phosphorus?

Answer:
Phosphorus is required for energy transfer (ATP) and root development.

Explanation:
It supports flowering, seed formation, and metabolism. Deficiency leads to stunted growth and dark green leaves.

Exam Tip:
Think “Phosphorus = flowers and energy”

Question 3

Question:
What is the function of potassium in plants?

Answer:
Potassium regulates water balance and activates enzymes for photosynthesis and respiration.

Explanation:
It strengthens stems and helps plants resist diseases. Deficiency shows as brown scorching on leaf edges.

Exam Tip:
Potassium = “strong stems + water regulation”

Question 4

Question:
Why is magnesium important for plants?

Answer:
Magnesium is a central component of chlorophyll.

Explanation:
It is required for photosynthesis. Deficiency causes interveinal chlorosis (yellowing between veins).

Exam Tip:
Remember: “Mg = chlorophyll center”

Question 5

Question:
What role does iron play in plant nutrition?

Answer:
Iron is needed for chlorophyll synthesis and enzyme functions.

Explanation:
Deficiency leads to pale young leaves while veins remain green.

Exam Tip:
Iron = “young leaves pale”

Question 6

Question:
How do plants absorb nutrients?

Answer:
Through roots from the soil, mostly as ions in water.

Explanation:
Root hairs increase surface area for efficient absorption of minerals and water.

Exam Tip:
Focus on root hair structure in diagrams

Question 7

Question:
Give two symptoms of nitrogen deficiency.

Answer:
Yellowing leaves and stunted growth.

Explanation:
Nitrogen is mobile; older leaves show deficiency first. Plants become weak.

Exam Tip:
Draw older leaf yellowing in diagrams

Question 8

Question:
What happens if a plant has potassium deficiency?

Answer:
Leaf edges turn brown, weak stems, and poor flower/fruit development.

Explanation:
Potassium is needed for enzyme activation and water regulation. Deficiency affects growth.

Exam Tip:
Label leaf edge scorching in diagrams

Question 9

Question:
Why is nitrogen considered a mobile nutrient?

Answer:
Because it can move from older leaves to younger growing parts.

Explanation:
Deficiency shows first in older leaves, while young leaves remain green.

Exam Tip:
Always note “older leaves affected first”

Question 10

Question:
How can nutrient deficiencies be corrected in plants?

Answer:
By applying the correct fertilizer containing the missing nutrient.

Explanation:
Fertilizers restore essential nutrients, promoting normal growth and development.

Exam Tip:
Mention specific nutrient and type of fertilizer

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Key Concepts Summary

• Essential plant nutrients: macro and micro elements
• Functions of nitrogen, phosphorus, potassium, magnesium, and iron
• Symptoms of nutrient deficiencies and mobility
• Methods of nutrient absorption through roots

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Frequently Asked Questions

What is the main function of potassium in plants?

Potassium helps in enzyme activation, photosynthesis, water regulation, and strengthens stems.

How can nutrient deficiencies be corrected?

Deficiencies are corrected by applying fertilizers containing the specific lacking nutrient.

Why is magnesium important for plants?

Magnesium is central to chlorophyll and essential for photosynthesis.

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Related Topics

• O Level Biology Photosynthesis Questions and Answers
• O Level Biology Enzymes Questions and Answers Live
• O Level Biology Respiration Questions and Answers Live 

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Conclusion

Understanding plant nutrition is key to mastering O Level Biology. Knowing the functions of nutrients, deficiency symptoms, and methods of absorption ensures better exam performance and practical application in plant care.