Transport in Plants – NEET Notes with MCQs & Concept Explanations
Transport of Water in Plants
Plants require a transport system to carry waste products, nutrients, and oxygen, much like people do. However, they employ a different tactic because they lack a heart and blood vessels: active transport, diffusion, osmosis, and specific tissues (xylem and phloem).
Since MCQs frequently cover topics like water potential, osmosis, transpiration, and phloem transport, this chapter is crucial for NEET students.
Since MCQs frequently cover topics like water potential, osmosis, transpiration, and phloem transport, this chapter is crucial for NEET students.
1. Root Absorption
Osmosis is how root hairs take up water.
Three routes allow water to enter the root cortex:
Via cell walls is the apoplast route.
Symplast pathway: Via plasmodesmata in the cytoplasm.
Across membranes is the transmembrane route.
2. Xylem Transport (Sap Ascent)
Water rises against gravity according to the Root Pressure Theory. Water is forced upward by positive pressure from the roots. operates on little plants.
Main Idea of Cohesion-Tension Theory:
Water is drawn upward by transpiration.
The xylem's negative pressure aids in drawing the water column upward.
Osmosis is how root hairs take up water.
Three routes allow water to enter the root cortex:
Via cell walls is the apoplast route.
Symplast pathway: Via plasmodesmata in the cytoplasm.
Across membranes is the transmembrane route.
2. Xylem Transport (Sap Ascent)
Water rises against gravity according to the Root Pressure Theory. Water is forced upward by positive pressure from the roots. operates on little plants.
Main Idea of Cohesion-Tension Theory:
Water is drawn upward by transpiration.
The xylem's negative pressure aids in drawing the water column upward.
3. Expiration
water vapor lost through stomata.
Functions:
generates transpiration pull, which aids in sap ascent.
keeps plants at a consistent temperature.
permits the exchange of gases.
Transpiration is influenced by light, temperature, humidity, wind, and water availability.
Food Transport: Phloem Transport
Plants need phloem to carry sugars, primarily sucrose.
The main theory is the pressure flow (mass flow) hypothesis.
1. At the source (leaves), sugars are actively loaded into phloem.
2. Water enters through osmosis, lowering water potential.
3. As the pressure increases, sucrose is forced toward the sink (roots, fruits, seeds).
4. Pressure decreases as sugars are dumped at the sink.
NEET MCQs with Concept Explanations
Q1. The main water-conducting tissue in plants is:A) Phloem
B) Xylem
C) Parenchyma
D) Collenchyma
Answer: B) Xylem
Concept Explanation: Xylem = water, Phloem = food.
Q2. Transpiration pull is due to:
A) Root pressure
B) Cohesion and adhesion of water
C) Guttation
D) Osmotic pressure
Concept Explanation: Xylem = water, Phloem = food.
Q2. Transpiration pull is due to:
A) Root pressure
B) Cohesion and adhesion of water
C) Guttation
D) Osmotic pressure
Answer: B) Cohesion and adhesion of water
Concept Explanation: Cohesion-Tension theory explains ascent of sap in tall trees.
Q3. Which pathway is blocked by Casparian strip in roots?
A) Apoplast
B) Symplast
C) Transmembrane
D) Both apoplast and symplast
Concept Explanation: Cohesion-Tension theory explains ascent of sap in tall trees.
Q3. Which pathway is blocked by Casparian strip in roots?
A) Apoplast
B) Symplast
C) Transmembrane
D) Both apoplast and symplast
Answer: A) Apoplast
Concept Explanation: Casparian strip (suberin layer) forces water into the symplast pathway.
Q4. In phloem transport, food is transported in which form?
A) Glucose
B) Starch
C) Sucrose
D) Fructose
Concept Explanation: Casparian strip (suberin layer) forces water into the symplast pathway.
Q4. In phloem transport, food is transported in which form?
A) Glucose
B) Starch
C) Sucrose
D) Fructose
Answer: C) Sucrose
Concept Explanation: Food is always translocated as sucrose, not as starch or glucose.
Q5. Which of the following is true about xylem transport?
A) Active and bidirectional
B) Passive and unidirectional
C) Active and unidirectional
D) Passive and bidirectional
Q5. Which of the following is true about xylem transport?
A) Active and bidirectional
B) Passive and unidirectional
C) Active and unidirectional
D) Passive and bidirectional
Answer: B) Passive and unidirectional
Concept Explanation: Water moves passively (without ATP) in one direction (roots → leaves).
Q6. Loss of water in liquid form from hydathodes is called:
A) Transpiration
B) Guttation
C) Bleeding
D) Exudation
Concept Explanation: Water moves passively (without ATP) in one direction (roots → leaves).
Q6. Loss of water in liquid form from hydathodes is called:
A) Transpiration
B) Guttation
C) Bleeding
D) Exudation
Answer: B) Guttation
Concept Explanation: Guttation occurs at night or early morning when root pressure is high.
Q7. Phloem transport is explained best by:
A) Diffusion theory
B) Cohesion-Tension theory
C) Pressure Flow hypothesis
D) Root pressure
Concept Explanation: Guttation occurs at night or early morning when root pressure is high.
Q7. Phloem transport is explained best by:
A) Diffusion theory
B) Cohesion-Tension theory
C) Pressure Flow hypothesis
D) Root pressure
Answer: C) Pressure Flow hypothesis
Concept Explanation: Pressure Flow hypothesis (by Ernst Münch) is the most accepted for phloem transport.
Q8. Which factor reduces transpiration rate?
A) High temperature
B) High humidity
C) High light intensity
D) Strong wind
Concept Explanation: Pressure Flow hypothesis (by Ernst Münch) is the most accepted for phloem transport.
Q8. Which factor reduces transpiration rate?
A) High temperature
B) High humidity
C) High light intensity
D) Strong wind
Answer: B) High humidity
Concept Explanation: High humidity reduces water vapor gradient, lowering transpiration.
Concept Explanation: High humidity reduces water vapor gradient, lowering transpiration.
Q9. Which of the following is a passive process?
A) Active transport
B) Diffusion
C) Endocytosis
D) Sodium-potassium pump
Answer: B) Diffusion
Concept Explanation: Passive transport requires no energy (ATP). Molecules move along concentration gradient (high → low).
Q10. The pressure exerted by the protoplast against the cell wall is called:
A) Wall pressure
B) Turgor pressure
C) Osmotic pressure
D) Root pressure
Concept Explanation: Passive transport requires no energy (ATP). Molecules move along concentration gradient (high → low).
Q10. The pressure exerted by the protoplast against the cell wall is called:
A) Wall pressure
B) Turgor pressure
C) Osmotic pressure
D) Root pressure
Answer: B) Turgor pressure
Concept Explanation: When a cell swells by water uptake (osmosis), turgor pressure develops inside and pushes against the cell wall.
Q11. Which among the following shows plasmolysis?
A) Plant cell in distilled water
B) Plant cell in hypertonic solution
C) Animal cell in isotonic solution
D) Animal cell in hypotonic solution
Concept Explanation: When a cell swells by water uptake (osmosis), turgor pressure develops inside and pushes against the cell wall.
Q11. Which among the following shows plasmolysis?
A) Plant cell in distilled water
B) Plant cell in hypertonic solution
C) Animal cell in isotonic solution
D) Animal cell in hypotonic solution
Answer: B) Plant cell in hypertonic solution
Concept Explanation: In hypertonic solution, water leaves the plant cell → protoplasm shrinks → cell shows plasmolysis.
Q12. Cohesion-tension theory of water transport was proposed by:
A) Dixon and Jolly
B) Strasburger
C) Nernst
D) Haberlandt
Concept Explanation: In hypertonic solution, water leaves the plant cell → protoplasm shrinks → cell shows plasmolysis.
Q12. Cohesion-tension theory of water transport was proposed by:
A) Dixon and Jolly
B) Strasburger
C) Nernst
D) Haberlandt
Answer: A) Dixon and Jolly
Concept Explanation: Dixon & Jolly (1894) explained ascent of sap: water rises in xylem due to transpiration pull + cohesion of water molecules.
Q13. Movement of food (sucrose) in phloem occurs by:
A) Diffusion
B) Active transport
C) Osmosis
D) Simple diffusion
Concept Explanation: Dixon & Jolly (1894) explained ascent of sap: water rises in xylem due to transpiration pull + cohesion of water molecules.
Q13. Movement of food (sucrose) in phloem occurs by:
A) Diffusion
B) Active transport
C) Osmosis
D) Simple diffusion
Answer: B) Active transport
Concept Explanation: Phloem transport requires energy (ATP) for loading/unloading sucrose → called pressure flow hypothesis (Münch, 1930).
Q14. Which plant part mainly absorbs water?
A) Root hair
B) Xylem
C) Phloem
D) Stomata
Concept Explanation: Phloem transport requires energy (ATP) for loading/unloading sucrose → called pressure flow hypothesis (Münch, 1930).
Q14. Which plant part mainly absorbs water?
A) Root hair
B) Xylem
C) Phloem
D) Stomata
Answer: A) Root hair
Concept Explanation: Root hairs (unicellular extensions of epidermis) increase surface area for absorption of water & minerals.
Q15. Which condition favors maximum transpiration?
A) High humidity
B) Low temperature
C) High temperature & low humidity
D) No wind
Q15. Which condition favors maximum transpiration?
A) High humidity
B) Low temperature
C) High temperature & low humidity
D) No wind
Answer: C) High temperature & low humidity
Concept Explanation: Hot, dry, windy conditions → transpiration rate increases. High humidity reduces transpiration.
Q16. Which of the following is NOT a function of transpiration?
A) Cooling effect
B) Ascent of sap
C) Exchange of gases
D) Maintaining water potential
Q16. Which of the following is NOT a function of transpiration?
A) Cooling effect
B) Ascent of sap
C) Exchange of gases
D) Maintaining water potential
Answer: C) Exchange of gases
Concept Explanation: Exchange of gases is a function of stomata, not transpiration. Transpiration helps in cooling, water movement, and mineral transport.
Q17. What is apoplastic pathway?
A) Movement through plasmodesmata
B) Movement through cytoplasm
C) Movement through cell wall and intercellular spaces
D) Active transport in phloem
Q17. What is apoplastic pathway?
A) Movement through plasmodesmata
B) Movement through cytoplasm
C) Movement through cell wall and intercellular spaces
D) Active transport in phloem
Answer: C) Movement through cell wall and intercellular spaces
Concept Explanation: Water travels via two main pathways in roots:
Apoplast → through cell wall & spaces (faster)
Symplast → through cytoplasm via plasmodesmata
Q18. The Casparian strip is present in:
A) Cortex
B) Endodermis
C) Pericycle
D) Epidermis
Apoplast → through cell wall & spaces (faster)
Symplast → through cytoplasm via plasmodesmata
Q18. The Casparian strip is present in:
A) Cortex
B) Endodermis
C) Pericycle
D) Epidermis
Answer: B) Endodermis
Concept Explanation: The Casparian strip (suberin layer) in endodermis blocks apoplast movement → forces water into symplast for selective uptake.
Concept Explanation: The Casparian strip (suberin layer) in endodermis blocks apoplast movement → forces water into symplast for selective uptake.
Q19. Guttation occurs through:
A) Stomata
B) Hydathodes
C) Lenticles
D) Root hairs
A) Stomata
B) Hydathodes
C) Lenticles
D) Root hairs
Answer: B) Hydathodes
Concept Explanation: At night / high soil water pressure, water is exuded in liquid form via hydathodes (leaf tips) → called guttation.
Q20. Which force is least significant in water movement in tall trees?
A) Root pressure
B) Transpiration pull
C) Cohesion of water molecules
D) Adhesion of water molecules
Concept Explanation: At night / high soil water pressure, water is exuded in liquid form via hydathodes (leaf tips) → called guttation.
Q20. Which force is least significant in water movement in tall trees?
A) Root pressure
B) Transpiration pull
C) Cohesion of water molecules
D) Adhesion of water molecules
Answer: A) Root pressure
Concept Explanation: Root pressure works in small plants, but in tall trees (100+ m), only transpiration pull + cohesion tension is effective.
Q21. The main form of sugar translocated in phloem is:
A) Glucose
B) Fructose
C) Sucrose
D) Maltose
Q21. The main form of sugar translocated in phloem is:
A) Glucose
B) Fructose
C) Sucrose
D) Maltose
Answer: C) Sucrose
Concept Explanation: Phloem sap mainly contains sucrose, along with amino acids, hormones, and some ions.
Q22. Which process maintains water potential gradient in plants?
A) Guttation
B) Photosynthesis
C) Transpiration
D) Respiration
Concept Explanation: Phloem sap mainly contains sucrose, along with amino acids, hormones, and some ions.
Q22. Which process maintains water potential gradient in plants?
A) Guttation
B) Photosynthesis
C) Transpiration
D) Respiration
Answer: C) Transpiration
Concept Explanation: Transpiration creates low water potential at leaves, which pulls water upward from roots.
Q23. Which mineral is required for opening & closing of stomata?
A) Potassium
B) Calcium
C) Magnesium
D) Sodium
Q23. Which mineral is required for opening & closing of stomata?
A) Potassium
B) Calcium
C) Magnesium
D) Sodium
Answer: A) Potassium
Concept Explanation: Stomatal movement depends on K⁺ ions:
Concept Explanation: Stomatal movement depends on K⁺ ions:
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