MCQs / Biology / O Level Biology: Plant Nutrition

O Level Biology: Plant Nutrition MCQs — Biology

26 multiple-choice questions on O Level Biology: Plant Nutrition from Biology, each with the correct answer and, where available, a teacher's explanation. Read through them to revise the chapter, then practise the same questions one by one to test yourself.

1. Why is a leaf boiled in ethanol when testing for starch?

  1. To kill bacteria
  2. To remove the chlorophyll
  3. To add starch
  4. To make it photosynthesise

Answer: B) To remove the chlorophyll

Explanation: Removing chlorophyll lets the iodine colour be seen. O Level Biology · Topic 6 Plant Nutrition · 6.1 Photosynthesis

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2. Plants take mineral ions from the soil through

  1. stomata
  2. palisade cells
  3. phloem
  4. root hair cells

Answer: D) root hair cells

Explanation: Root hair cells absorb ions, often by active transport. O Level Biology · Topic 6 Plant Nutrition · 6.3 Mineral nutrition

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3. What is the word equation for photosynthesis?

  1. oxygen + water → glucose + carbon dioxide
  2. carbon dioxide + water → glucose + oxygen
  3. glucose → ethanol + carbon dioxide
  4. glucose + oxygen → carbon dioxide + water

Answer: B) carbon dioxide + water → glucose + oxygen

Explanation: Photosynthesis uses CO₂ and water to make glucose and oxygen. O Level Biology · Topic 6 Plant Nutrition · 6.1 Photosynthesis

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4. What is the function of the guard cells?

  1. To make the cuticle
  2. To transport water
  3. To store starch
  4. To open and close the stomata

Answer: D) To open and close the stomata

Explanation: Guard cells control stomatal opening. O Level Biology · Topic 6 Plant Nutrition · 6.2 Leaf structure

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5. Which cells in the epidermis contain chloroplasts?

  1. All epidermal cells
  2. Cuticle cells
  3. No epidermal cells
  4. Guard cells

Answer: D) Guard cells

Explanation: Only guard cells in the epidermis have chloroplasts. O Level Biology · Topic 6 Plant Nutrition · 6.2 Leaf structure

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6. A plant grown without magnesium has

  1. purple leaves
  2. extra flowers
  3. very large leaves
  4. yellow leaves

Answer: D) yellow leaves

Explanation: Without chlorophyll, leaves become yellow. O Level Biology · Topic 6 Plant Nutrition · 6.3 Mineral nutrition

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7. The role of chlorophyll is to

  1. store starch
  2. transfer light energy into chemical energy
  3. absorb carbon dioxide
  4. make cellulose

Answer: B) transfer light energy into chemical energy

Explanation: Chlorophyll traps light energy. O Level Biology · Topic 6 Plant Nutrition · 6.1 Photosynthesis

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8. A variegated leaf is tested for starch. Only the green parts turn blue-black. This shows that

  1. light is needed
  2. carbon dioxide is needed
  3. chlorophyll is needed for photosynthesis
  4. water is needed

Answer: C) chlorophyll is needed for photosynthesis

Explanation: White parts lack chlorophyll and made no starch. O Level Biology · Topic 6 Plant Nutrition · 6.1 Photosynthesis

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9. The air spaces in the spongy mesophyll

  1. allow carbon dioxide to diffuse to the cells
  2. store water
  3. carry sugar
  4. protect the leaf

Answer: A) allow carbon dioxide to diffuse to the cells

Explanation: Gases diffuse through the air spaces. O Level Biology · Topic 6 Plant Nutrition · 6.2 Leaf structure

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10. Soda lime is used in a photosynthesis experiment to

  1. provide light
  2. provide carbon dioxide
  3. remove water
  4. absorb carbon dioxide

Answer: D) absorb carbon dioxide

Explanation: Soda lime removes CO₂. O Level Biology · Topic 6 Plant Nutrition · 6.1 Photosynthesis

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11. Starch is used as a store because it is

  1. needed for cell walls
  2. a protein
  3. soluble and easily transported
  4. insoluble and does not affect osmosis

Answer: D) insoluble and does not affect osmosis

Explanation: Insoluble starch has no osmotic effect. O Level Biology · Topic 6 Plant Nutrition · 6.1 Photosynthesis

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12. On a graph, the rate of photosynthesis rises with light intensity and then levels off. In the levelled-off part,

  1. photosynthesis has stopped
  2. another factor such as CO₂ or temperature is limiting
  3. the plant is dead
  4. light is limiting

Answer: B) another factor such as CO₂ or temperature is limiting

Explanation: When the graph is flat, light is no longer the limiting factor. O Level Biology · Topic 6 Plant Nutrition · 6.1 Photosynthesis

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13. Why does the rate of photosynthesis fall at very high temperatures?

  1. Light is absorbed less
  2. Enzymes are denatured
  3. Chlorophyll is made faster
  4. There is too much carbon dioxide

Answer: B) Enzymes are denatured

Explanation: Photosynthesis is enzyme-controlled. O Level Biology · Topic 6 Plant Nutrition · 6.1 Photosynthesis

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14. Why is the upper epidermis transparent?

  1. To store water
  2. To exchange gases
  3. To let light reach the palisade cells
  4. To make sugar

Answer: C) To let light reach the palisade cells

Explanation: Light passes through to the mesophyll. O Level Biology · Topic 6 Plant Nutrition · 6.2 Leaf structure

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15. An aquatic plant is used to measure the rate of photosynthesis by

  1. counting bubbles of oxygen per minute
  2. counting stomata
  3. measuring the leaf area
  4. measuring starch

Answer: A) counting bubbles of oxygen per minute

Explanation: Oxygen bubbles show the rate. O Level Biology · Topic 6 Plant Nutrition · 6.1 Photosynthesis

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16. Which is the balanced equation for photosynthesis?

  1. 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
  2. 6CO₂ + 12H₂O → C₆H₁₂O₆
  3. CO₂ + H₂O → C₆H₁₂O₆ + O₂
  4. C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Answer: A) 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Explanation: Six of each reactant, one glucose and six oxygen. O Level Biology · Topic 6 Plant Nutrition · 6.1 Photosynthesis

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17. Why is a plant kept in the dark for 48 hours before a starch test experiment?

  1. To increase photosynthesis
  2. To kill the leaves
  3. To remove starch from its leaves
  4. To remove chlorophyll

Answer: C) To remove starch from its leaves

Explanation: Destarching ensures any starch found was made during the experiment. O Level Biology · Topic 6 Plant Nutrition · 6.1 Photosynthesis

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18. Hydrogencarbonate indicator turns purple near a plant in bright light because

  1. respiration adds carbon dioxide
  2. oxygen turns it purple
  3. light turns it purple
  4. photosynthesis removes carbon dioxide

Answer: D) photosynthesis removes carbon dioxide

Explanation: Low CO₂ makes the indicator purple. O Level Biology · Topic 6 Plant Nutrition · 6.1 Photosynthesis

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19. Which tissue in the leaf carries water to the mesophyll cells?

  1. Epidermis
  2. Phloem
  3. Cuticle
  4. Xylem

Answer: D) Xylem

Explanation: Xylem transports water and minerals. O Level Biology · Topic 6 Plant Nutrition · 6.2 Leaf structure

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20. Which layer of the leaf carries out most photosynthesis?

  1. Palisade mesophyll
  2. Lower epidermis
  3. Upper epidermis
  4. Spongy mesophyll

Answer: A) Palisade mesophyll

Explanation: Palisade cells are packed with chloroplasts near the light. O Level Biology · Topic 6 Plant Nutrition · 6.2 Leaf structure

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21. Most stomata are found in the

  1. upper epidermis
  2. palisade layer
  3. vascular bundle
  4. lower epidermis

Answer: D) lower epidermis

Explanation: Stomata are mostly on the lower surface. O Level Biology · Topic 6 Plant Nutrition · 6.2 Leaf structure

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22. Nitrate ions are used by plants to make

  1. amino acids and proteins
  2. chlorophyll only
  3. glucose
  4. cellulose

Answer: A) amino acids and proteins

Explanation: Nitrogen is needed for amino acids. O Level Biology · Topic 6 Plant Nutrition · 6.3 Mineral nutrition

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23. Leaves are thin so that

  1. they lose more water
  2. they can store more starch
  3. gases have a short distance to diffuse
  4. they can grow faster

Answer: C) gases have a short distance to diffuse

Explanation: Thin leaves give a short diffusion path. O Level Biology · Topic 6 Plant Nutrition · 6.2 Leaf structure

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24. In which form is sugar transported in the phloem?

  1. Glucose
  2. Sucrose
  3. Cellulose
  4. Starch

Answer: B) Sucrose

Explanation: Sucrose is the transport sugar. O Level Biology · Topic 6 Plant Nutrition · 6.1 Photosynthesis

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25. A plant lacking nitrate ions shows

  1. larger fruits
  2. poor, stunted growth
  3. faster growth
  4. more chlorophyll

Answer: B) poor, stunted growth

Explanation: Without nitrate it cannot make proteins for growth. O Level Biology · Topic 6 Plant Nutrition · 6.3 Mineral nutrition

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