CBSE Class 11 Biology Chapter 11: Transport in Plants NCERT Solutions

Reviewed by NCERT Help Editorial Team · Updated on 29 Jul 2026

NCERT Solutions PDF Class 11 PDF

This resource provides detailed NCERT Solutions for CBSE Class 11 Biology, Chapter 11: Transport in Plants. It covers essential concepts such as the factors affecting diffusion, the role of porins, the mechanism of active transport via protein pumps, and the explanation of water potential, including why pure water has the maximum potential. The solutions also offer clear differentiations between key related processes like diffusion and osmosis, transpiration and evaporation, osmotic pressure and osmotic potential, imbibition and diffusion, apoplast and symplast pathways, and guttation and transpiration. These explanations are designed to help students grasp the fundamental principles of how substances move within plant organisms, aiding in their understanding and exam preparation.

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Quick info

Board	CBSE
Class	Class 11
Subject	Biology
Session	2026
Language	English
Type	NCERT Solutions
Chapter	Chapter 11: Transport in Plants

Chapter summary

Chapter 11 of the CBSE Class 11 Biology syllabus focuses on Transport in Plants. This NCERT Solutions set breaks down complex topics like diffusion, osmosis, active transport, and water potential. It clarifies the factors influencing these processes, the function of specialized structures like porins, and the pathways water takes through the plant. The solutions also provide crucial comparisons between related physiological and physical processes, ensuring a thorough understanding for students.

Learning outcomes

Understand the factors influencing the rate of diffusion in plants.
Explain the function of porins in membrane transport.
Describe the process and energy requirements of active transport.
Define water potential and explain why pure water has the maximum value.
Differentiate between key transport processes like diffusion, osmosis, transpiration, and evaporation.
Distinguish between apoplast and symplast pathways for water movement.
Compare guttation and transpiration.

Topics covered

Paper topics

Diffusion
Factors affecting diffusion
Porins
Active Transport
Protein Pumps
Water Potential
Pure Water Potential
Osmosis
Transpiration
Evaporation
Apoplast Pathway
Symplast Pathway

Important topics

Water Potential
Diffusion vs. Osmosis
Active Transport Mechanism
Apoplast and Symplast Pathways
Factors Affecting Transport

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Questions and Solutions

Question 1

What are the factors affecting the rate of diffusion?

Solution: Diffusion is defined as the passive movement of any substance from a region where its concentration is higher to a region where its concentration is lower. In plants, the diffusion of various substances is crucial for cellular transport. Several factors influence how quickly diffusion occurs:

Concentration Gradient: The greater the difference in concentration between two regions, the faster the rate of diffusion. Diffusion continues until the concentrations become equal on both sides of a barrier.
Membrane Permeability: The ease with which a substance can pass through a membrane significantly affects diffusion. A more permeable membrane allows for a faster diffusion rate.
Temperature: Higher temperatures increase the kinetic energy of molecules, leading to faster movement and thus a higher rate of diffusion.
Pressure: Pressure, particularly partial pressure for gases, plays a role. Gases diffuse from an area of higher partial pressure to an area of lower partial pressure.

Question 2

What are porins? What role do they play in diffusion?

Solution: Porins are a class of proteins that form large-sized pores or channels. These proteins are primarily found in the outer membranes of certain organelles, such as chloroplasts and mitochondria, and also in the outer membranes of bacteria. Their main role is to facilitate the passive transport of small-sized molecules, including proteins, across these membranes. By creating these large pores, porins allow for the relatively free passage of specific substances, contributing to the overall transport processes within the cell.

Question 3

Describe the role played by protein pumps during active transport in plants.

Solution: In plant cells, active transport is the mechanism used to move substances across a cell membrane against their concentration gradient, meaning from an area of lower concentration to an area of higher concentration. This process requires energy and involves specific protein pumps embedded within the membrane. These protein pumps are typically trans-membrane proteins. The process works as follows:

The protein pump binds to the specific substance that needs to be transported.
Using energy, usually derived from the hydrolysis of ATP, the protein pump undergoes a conformational change.
This change facilitates the movement of the substance across the membrane.
Once across, the substance is released into the cytoplasm as the protein-substance complex dissociates.

This energy-dependent process ensures that essential substances can be accumulated within the cell even when their external concentration is low.

Question 4

Explain why pure water has the maximum water potential.

Solution: Water potential (

\Psi

) is a measure that quantifies the tendency of water to move from one location to another during various biological processes. It is expressed in pressure units. The water potential of pure water is considered the maximum and is conventionally set to zero at standard temperature and pressure. This can be understood by considering the kinetic energy of water molecules. In pure liquid water, the molecules are in constant, rapid motion, possessing high kinetic energy. This high concentration of water molecules and their inherent energy contribute to its maximum potential to move. When a solute is dissolved in water, the concentration of water molecules decreases, and the solute molecules interfere with the movement of water molecules. This interaction lowers the kinetic energy of water and thus reduces its water potential, making it negative relative to pure water.

Question 5

Differentiate between the following:

Diffusion and Osmosis
Transpiration and Evaporation
Osmotic Pressure and Osmotic Potential
Imbibition and Diffusion
Apoplast and Symplast pathways of movement of water in plants.
Guttation and Transpiration.

Solution:

Diffusion and Osmosis

Diffusion	Osmosis
It is the passive movement of particles, ions, and molecules along their concentration gradient (from higher to lower concentration).	It is a specific type of diffusion involving the movement of solvent molecules (usually water) across a semi-permeable membrane from a region of higher solvent concentration (lower solute concentration) to a region of lower solvent concentration (higher solute concentration).
It can occur in solids, liquids, and gases.	It occurs primarily in the liquid medium.
It does not require a semi-permeable membrane.	It requires a semi-permeable membrane.

Transpiration and Evaporation

Transpiration	Evaporation
It is the loss of water vapor specifically from the aerial parts of plants, mainly through stomata. It is a physiological process.	It is the physical process of water changing into vapor from any free surface (like soil, water bodies, or plant surfaces). It can occur from both living and non-living surfaces.
It is regulated by the plant, involving stomatal opening and closing.	It is a purely physical process influenced by environmental factors like temperature, humidity, and wind.

Osmotic Pressure and Osmotic Potential

Osmotic Pressure	Osmotic Potential
It is the pressure required to prevent the inward flow of solvent (water) across a semi-permeable membrane into a solution. It is always a positive value.	It is a measure of the tendency of water to move by osmosis. It is always a negative value (or zero for pure water) and is directly related to the solute concentration. A higher solute concentration leads to a more negative osmotic potential.
It is the force that drives osmosis into a solution.	It represents the reduction in water potential due to the presence of solutes.

Imbibition and Diffusion

Imbibition	Diffusion
It is a special type of diffusion where water is absorbed by solid substances (like cellulose, proteins) causing them to swell. It involves adsorption of water.	It is the general movement of any substance (solid, liquid, or gas) from a region of higher concentration to a region of lower concentration.
It requires a hydrophilic surface and a liquid.	It does not require a specific surface; it occurs in a medium.
It leads to an increase in volume.	It leads to the equalization of concentration.

Apoplast and Symplast Pathways

Apoplast Pathway	Symplast Pathway
Movement of water occurs exclusively through the non-living parts of the plant, such as cell walls and intercellular spaces. It is a faster pathway.	Movement of water occurs through the living parts of the plant, i.e., the cytoplasm of cells. Water moves from cell to cell via plasmodesmata, which are cytoplasmic connections between adjacent cells.
It does not involve crossing cell membranes.	It involves crossing cell membranes at least once (to enter the symplast).

Guttation and Transpiration

Guttation	Transpiration
It is the loss of water in the form of liquid droplets from the tips or margins of leaves, typically occurring through specialized structures called hydathodes. It usually happens when transpiration is inhibited (e.g., at night or high humidity) and root pressure is high.	It is the loss of water in the form of water vapor from the aerial parts of plants, primarily through stomata. It is a major process influencing water movement in plants.
The lost water is in liquid form.	The lost water is in vapor form.
It occurs through hydathodes.	It occurs mainly through stomata.

Common mistakes

Confusing passive transport (diffusion, osmosis) with active transport.
Misunderstanding the direction of movement in osmosis (solute vs. solvent).
Not clearly differentiating between physiological processes (transpiration) and physical processes (evaporation).
Incorrectly defining or comparing osmotic pressure and osmotic potential.

Revision tips

Focus on understanding the definitions and conditions for each transport process.
Create flashcards to quickly differentiate between similar terms like diffusion/osmosis and transpiration/evaporation.
Pay close attention to the role of energy (ATP) in active transport.
Visualize the movement of water molecules and solutes across membranes.
Review the diagrams (if available in the textbook) illustrating apoplast and symplast pathways.

Practice MCQs

Q1. Which of the following factors does NOT directly affect the rate of diffusion?

Q2. Porins are proteins that form large pores in the outer membranes of which organelles?

Q3. Active transport in plants moves substances:

Q4. What is the water potential of pure water at standard temperature and pressure?

Q5. Which process involves the movement of solvent molecules across a semi-permeable membrane?

Frequently asked questions

What is diffusion and what affects its rate?

Diffusion is the passive movement of substances from an area of higher concentration to an area of lower concentration. Its rate is affected by the concentration gradient, membrane permeability, temperature, and pressure.

What is the role of porins in plants?

Porins are proteins that form large pores in the outer membranes of organelles like chloroplasts and mitochondria, as well as in bacterial membranes. They facilitate the passive transport of small molecules across these membranes.

How does active transport differ from passive transport?

Active transport moves substances against their concentration gradient (from low to high concentration) and requires energy, usually from ATP, and specific protein pumps. Passive transport, like diffusion and osmosis, moves substances down their concentration gradient and does not require metabolic energy.

Why is the water potential of pure water considered zero?

The water potential of pure water is defined as zero at standard temperature and pressure. This serves as a reference point. Any dissolved solute lowers the water potential, making it negative.

What are the key differences between transpiration and evaporation?

Transpiration is the loss of water vapor specifically from plant surfaces (stomata, lenticels), a physiological process. Evaporation is the physical process of water turning into vapor from any free surface, occurring in both living and non-living contexts.

What are the apoplast and symplast pathways for water movement?

The apoplast pathway involves water movement through non-living parts of the plant (cell walls, intercellular spaces). The symplast pathway involves water movement through the living cytoplasm of cells, connected via plasmodesmata.

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