CBSE Class 11 Biology – Transport in Plants | Case-Based / Source-Based Questions with Answers (NCERT Based)

Course & Examination Details

Course: CBSE Class 11 Biology
Unit: Unit IV – Plant Physiology
Chapter: Chapter 11 – Transport in Plants
Prescribed Textbook: NCERT
Board: CBSE

CBSE Board Examination Context

• Case-based questions assess application of concepts
• Introduced to test analytical and reasoning skills
• Answers must be conceptual, NCERT-specific, and logically explained
• Frequently framed from daily life and experimental situations

Section A: Diffusion (Case-Based Questions 1–6)

Case 1

A student observed that carbon dioxide enters leaf tissues during photosynthesis without the use of energy.

Q1. Identify the process involved.
Ans: The process involved is diffusion, which is a passive movement of molecules from higher to lower concentration without energy expenditure.

Q2. Why does this process not require energy?
Ans: It does not require energy because molecules move naturally along the concentration gradient due to their kinetic energy.

Case 2

Oxygen produced during photosynthesis moves out of leaf cells into the atmosphere.

Q3. Name the mechanism responsible for this movement.
Ans: Diffusion is responsible for the outward movement of oxygen from leaf cells into the atmosphere.

Q4. Why is diffusion suitable only for short distances?
Ans: Diffusion is slow and non-directional, making it effective only across short distances such as cell membranes.

Case 3

A tall tree cannot depend on diffusion alone for water movement.

Q5. Why is diffusion insufficient in tall plants?
Ans: Diffusion is too slow to transport water over long distances, hence vascular tissues are required.

Q6. Which tissue replaces diffusion for long-distance transport?
Ans: Xylem replaces diffusion by enabling rapid, directional transport of water and minerals.

Section B: Osmosis (Case-Based Questions 7–13)

Case 4

A potato strip placed in salt solution shrinks after some time.

Q7. Identify the process involved.
Ans: The process involved is exosmosis, a type of osmosis where water moves out of the cell.

Q8. Why does the potato strip shrink?
Ans: Water leaves the potato cells due to lower water potential of the surrounding hypertonic solution.

Case 5

A root hair cell absorbs water continuously from the soil.

Q9. Which process allows this absorption?
Ans: Osmosis allows water absorption by root hair cells.

Q10. Why does water move into the root hair?
Ans: Soil water has higher water potential compared to the cell sap of root hair cells.

Case 6

A plant cell placed in distilled water becomes swollen.

Q11. What condition does the cell attain?
Ans: The cell becomes turgid due to osmotic entry of water.

Q12. Why does the cell not burst?
Ans: The rigid cell wall exerts wall pressure that prevents bursting.

Case 7

Guard cells swell during daytime.

Q13. How does osmosis regulate this process?
Ans: Osmotic entry of water makes guard cells turgid, causing stomatal opening.

Section C: Transpiration (Case-Based Questions 14–19)

Case 8

A well-watered plant wilts on a hot, dry afternoon.

Q14. Which process causes this temporary wilting?
Ans: Excessive transpiration causes temporary wilting.

Q15. Why does high temperature increase transpiration?
Ans: High temperature increases evaporation of water from leaf surfaces.

Case 9

Plants kept in humid conditions show reduced water loss.

Q16. Which factor is responsible for reduced transpiration?
Ans: High humidity reduces the diffusion gradient of water vapour.

Case 10

A leaf covered with petroleum jelly shows reduced water loss.

Q17. Which type of transpiration is reduced?
Ans: Stomatal transpiration is reduced due to blockage of stomata.

Case 11

Windy conditions increase water loss from leaves.

Q18. How does wind affect transpiration?
Ans: Wind removes moist air around leaves, maintaining diffusion gradient.

Case 12

Plants appear cooler during transpiration.

Q19. Why does transpiration cause cooling?
Ans: Evaporation of water absorbs heat energy, cooling the plant body.

Section D: Water and Mineral Transport (Case-Based Questions 20–25)

Case 13

Water moves upward in a tall tree even without pumps.

Q20. Which theory explains this movement?
Ans: The cohesion–tension theory explains upward water movement.

Case 14

Water forms a continuous column in xylem vessels.

Q21. Which property of water maintains this column?
Ans: Cohesion between water molecules maintains the continuous column.

Case 15

Roots absorb minerals even against concentration gradient.

Q22. Which mechanism enables this absorption?
Ans: Active transport enables mineral absorption against gradient.

Case 16

Water moves through cell walls before entering xylem.

Q23. Name the pathway involved.
Ans: The apoplast pathway allows water movement through cell walls.

Case 17

Minerals absorbed by roots reach leaves efficiently.

Q24. Which tissue transports minerals upward?
Ans: Xylem transports water and dissolved minerals upward.

Case 18

Root pressure is observed during early morning guttation.

Q25. Why is root pressure insufficient in tall trees?
Ans: Root pressure is weak and cannot lift water to great heights, unlike transpiration pull.

Best Suited For

• CBSE Class 11 Annual Examinations
• NCERT-based internal assessments
• Competency-based and case-study questions practice