CBSE Class 11 Biology – Transport in Plants | Very Short Answer Questions with Answers (NCERT Based)

Course 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 Focus

• VSA questions carry high scoring potential
• Frequently asked in annual exams
• Test definitions, principles, and core concepts
• Answers must be precise, accurate, and NCERT-based

Section A: Diffusion (Questions 1–12)

Q1. What is diffusion?
Ans: Diffusion is the passive movement of molecules from a region of higher concentration to a region of lower concentration until equilibrium is established.

Q2. Name the driving force behind diffusion.
Ans: The driving force for diffusion is the concentration gradient, which causes molecules to move spontaneously without expenditure of metabolic energy.

Q3. Does diffusion require energy? Explain briefly.
Ans: Diffusion does not require energy because it is a passive process driven by kinetic energy of molecules and concentration differences.

Q4. Mention one role of diffusion in plants.
Ans: Diffusion facilitates gaseous exchange of oxygen and carbon dioxide during respiration and photosynthesis through stomata and lenticels.

Q5. How does temperature affect diffusion?
Ans: Increase in temperature increases kinetic energy of molecules, thereby increasing the rate of diffusion in plant cells and tissues.

Q6. Is diffusion directional? Give reason.
Ans: Diffusion is non-directional as molecules move randomly in all directions, though net movement occurs along the concentration gradient.

Q7. Name two substances that diffuse in plants.
Ans: Oxygen and carbon dioxide commonly diffuse in plants during respiration and photosynthesis through intercellular spaces and stomata.

Q8. Why is diffusion slow over long distances?
Ans: Diffusion is slow over long distances because it depends only on random molecular movement and lacks a driving force for bulk transport.

Q9. Which plant structures aid diffusion of gases?
Ans: Stomata in leaves and lenticels in woody stems aid diffusion of respiratory gases between plant tissues and the atmosphere.

Q10. Can diffusion occur in solids?
Ans: Yes, diffusion can occur in solids, but it is extremely slow due to limited movement of molecules compared to liquids and gases.

Q11. How does molecular size affect diffusion?
Ans: Smaller molecules diffuse faster than larger molecules because they encounter less resistance during movement through a medium.

Q12. Why is diffusion important at cellular level?
Ans: Diffusion helps maintain cellular homeostasis by enabling exchange of gases and small molecules across cell membranes.

Section B: Osmosis (Questions 13–25)

Q13. Define osmosis.
Ans: Osmosis is the movement of water molecules across a semi-permeable membrane from a region of higher water potential to lower water potential.

Q14. What is a semi-permeable membrane?
Ans: A semi-permeable membrane allows passage of solvent molecules like water but restricts the movement of solute particles.

Q15. What happens to a plant cell in hypotonic solution?
Ans: In a hypotonic solution, water enters the cell by osmosis, making the plant cell turgid due to increased internal pressure.

Q16. Define plasmolysis.
Ans: Plasmolysis is the shrinkage of protoplasm away from the cell wall when a plant cell loses water in a hypertonic solution.

Q17. What is water potential?
Ans: Water potential is the measure of free energy of water that determines the direction of water movement in plant tissues.

Q18. Name two components of water potential.
Ans: Water potential consists of solute potential and pressure potential, which together regulate water movement in cells.

Q19. What happens in isotonic solution?
Ans: In an isotonic solution, there is no net movement of water as water potential inside and outside the cell remains equal.

Q20. How does osmosis help root hair cells?
Ans: Osmosis enables root hair cells to absorb water from soil, which has higher water potential compared to cell sap.

Q21. Why are plant cells not burst in hypotonic solution?
Ans: Plant cells do not burst due to the presence of rigid cell wall, which exerts counter pressure called wall pressure.

Q22. What is turgidity?
Ans: Turgidity is the condition of a plant cell when it becomes swollen due to osmotic entry of water, providing mechanical support.

Q23. Mention one role of osmosis in plants.
Ans: Osmosis helps in maintaining cell turgidity, which is essential for plant rigidity, growth, and stomatal movement.

Q24. Is osmosis possible without a membrane?
Ans: No, osmosis requires a semi-permeable membrane; without it, water movement occurs by diffusion, not osmosis.

Q25. How does solute concentration affect osmosis?
Ans: Higher solute concentration lowers water potential, causing water to move toward regions of higher solute concentration.

Section C: Transpiration (Questions 26–38)

Q26. Define transpiration.
Ans: Transpiration is the loss of water in the form of water vapour from aerial parts of plants, mainly through stomata.

Q27. Name the major site of transpiration.
Ans: Stomata present on leaf surfaces are the primary sites of transpiration in most terrestrial plants.

Q28. List the three types of transpiration.
Ans: Transpiration occurs through stomata, cuticle, and lenticels, termed stomatal, cuticular, and lenticular transpiration respectively.

Q29. Which type of transpiration is maximum?
Ans: Stomatal transpiration accounts for the maximum loss of water in plants due to numerous stomata on leaf surfaces.

Q30. How does light affect transpiration?
Ans: Light increases transpiration by causing stomatal opening, thereby enhancing diffusion of water vapour from leaves.

Q31. Name one internal factor affecting transpiration.
Ans: Leaf area is an internal factor; larger leaf area increases transpiration due to greater exposed surface.

Q32. What is transpiration pull?
Ans: Transpiration pull is the suction force generated by transpiration that helps in upward movement of water through xylem.

Q33. Why is transpiration called a necessary evil?
Ans: Transpiration causes water loss but is essential for mineral transport, cooling, and maintaining water movement in plants.

Q34. How does humidity affect transpiration?
Ans: High humidity reduces transpiration by decreasing the diffusion gradient of water vapour between leaf and atmosphere.

Q35. What role does transpiration play in cooling?
Ans: Transpiration cools plants by evaporation of water from leaf surfaces, preventing overheating during high temperatures.

Q36. How does wind affect transpiration?
Ans: Wind increases transpiration by removing moist air around leaves, maintaining a steep diffusion gradient.

Q37. Which tissue is indirectly dependent on transpiration?
Ans: Xylem transport of water and minerals is indirectly dependent on transpiration pull generated by leaf evaporation.

Q38. Does transpiration occur at night?
Ans: Transpiration is greatly reduced at night as stomata generally close in absence of light.

Section D: Water and Mineral Transport (Questions 39–50)

Q39. Name the tissue responsible for water transport.
Ans: Xylem is the vascular tissue responsible for upward transport of water and dissolved minerals in plants.

Q40. What is ascent of sap?
Ans: Ascent of sap refers to the upward movement of water and minerals from roots to aerial parts through xylem.

Q41. Name the most accepted theory of ascent of sap.
Ans: Cohesion–tension theory is the most widely accepted explanation for ascent of sap in tall plants.

Q42. Who proposed cohesion–tension theory?
Ans: The cohesion–tension theory was proposed by Dixon and Joly to explain water movement in plants.

Q43. What is cohesion in water transport?
Ans: Cohesion refers to the attraction between water molecules, maintaining an unbroken water column in xylem vessels.

Q44. Define adhesion.
Ans: Adhesion is the attraction between water molecules and xylem walls, helping maintain water column against gravity.

Q45. What is root pressure?
Ans: Root pressure is the positive pressure generated by osmotic ion uptake in roots, pushing water upward in xylem.

Q46. Is root pressure sufficient in tall trees?
Ans: Root pressure alone is insufficient in tall trees, hence transpiration pull plays a dominant role.

Q47. How are minerals absorbed by plants?
Ans: Minerals are absorbed by roots as ions through both passive diffusion and active transport mechanisms.

Q48. What is active absorption of minerals?
Ans: Active absorption requires energy and occurs against concentration gradient using carrier proteins in root cells.

Q49. Name two pathways of water movement in roots.
Ans: Water moves through roots via apoplast pathway and symplast pathway before entering xylem.

Q50. Why is water transport essential in plants?
Ans: Water transport supplies minerals, maintains turgidity, supports photosynthesis, and enables overall plant growth and survival.

Ideal For

• CBSE Class 11 Annual Exams
• NCERT-based school assessments
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