CBSE Class 11 Biology Chapter 13: Transport in Plants NCERT Solutions

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

NCERT Solutions PDF Class 11 PDF

CBSE Class 11 Biology Chapter 13, 'Transport in Plants,' NCERT Solutions, offers a comprehensive exploration of how plants move substances. It clarifies vital concepts such as the factors influencing diffusion, the function of porins in passive transport, and the energy-driven process of active transport via protein pumps. The solutions meticulously explain water potential, highlighting why pure water exhibits the highest potential. Furthermore, they provide clear distinctions between related phenomena like diffusion versus osmosis, transpiration versus evaporation, osmotic pressure versus osmotic potential, imbibition versus diffusion, apoplast versus symplast pathways, and guttation versus transpiration. These explanations are crafted to demystify complex plant physiology, enhance student comprehension, and serve as a valuable resource for effective exam preparation with accurate and accessible answers.

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Quick info

Board	CBSE
Class	Class 11
Subject	Biology
Session	2026
Language	English
Type	NCERT Solutions
Chapter	Chapter 13

Chapter summary

This chapter's NCERT Solutions for Class 11 Biology, 'Transport in Plants', explain the fundamental mechanisms by which substances move within plants. It covers passive transport processes like diffusion and osmosis, highlighting factors influencing them and the role of structures like porins. Active transport, driven by energy, is also detailed. Key concepts such as water potential and its components are clarified, along with distinctions between various transport and water movement phenomena like transpiration, evaporation, imbibition, and guttation, using comparative tables for clarity.

Learning outcomes

Understand the factors influencing the rate of diffusion.
Explain the function of porins in membrane transport.
Describe the process and components of active transport.
Define and explain water potential and its relation to pure water.
Differentiate between key transport and water movement processes in plants.

Topics covered

Paper topics

Diffusion
Factors affecting diffusion
Porins
Active Transport
Protein Pumps
Water Potential
Osmosis
Transpiration
Evaporation
Osmotic Pressure
Osmotic Potential
Imbibition
Apoplast Pathway
Symplast Pathway
Guttation

Important topics

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

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Questions and Solutions

Question 1

What are the factors affecting the rate of diffusion?

Solution: Diffusion is the passive movement of any substance from a region where it is in higher concentration to a region where it is in lower concentration. This process is fundamental to the transport of substances within plant cells. 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 equilibrium is reached, meaning the concentration is uniform throughout.
Membrane Permeability: For diffusion across a membrane, the membrane's permeability to the substance is crucial. A more permeable membrane allows for a faster rate of diffusion.
Temperature: Higher temperatures increase the kinetic energy of molecules, leading to faster movement and thus a higher rate of diffusion.
Pressure: Pressure differences, particularly partial pressure for gases, can drive diffusion. Gases move 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, water-filled pores or channels. These proteins are typically found in the outer membranes of certain organelles, such as mitochondria and plastids (like chloroplasts), as well as in the outer membranes of bacteria. Their primary role in diffusion is to facilitate the passive transport of small-sized molecules, particularly proteins, across these membranes. By providing channels, porins allow these molecules to move down their concentration gradient without requiring energy input.

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 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 cell membrane. These protein pumps are typically trans-membrane proteins. They function by binding to the specific substance that needs to be transported. Using energy, usually derived from the hydrolysis of ATP, the pump undergoes a conformational change. This change facilitates the movement of the substance across the membrane. Once the substance reaches the other side (e.g., the cytoplasm), the protein-substance complex dissociates, releasing the substance and allowing the pump to reset for another transport cycle.

Question 4

Explain why pure water has the maximum water potential.

Solution: Water potential (

\Psi

) is a measure of the free energy of water molecules per unit volume, indicating the tendency of water to move from one area to another. It is quantified using the Greek letter Psi (

\Psi

). Pure water, under standard temperature and pressure conditions, is considered to have the highest possible water potential, which is conventionally assigned a value of zero (

\Psi = 0

). This is because water molecules in pure water possess the maximum kinetic energy and are not influenced by any dissolved solutes or external pressures. When a solute is dissolved in water, it reduces the concentration of free water molecules and lowers their kinetic energy, thereby decreasing the water potential. Thus, any solution will have a water potential less than zero (i.e., negative).

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
The passive movement of particles, ions, or molecules from a region of higher concentration to a region of lower concentration.	The diffusion of a solvent (typically 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).
Can occur in solids, liquids, and gases.	Occurs primarily in liquids.
Does not require a semi-permeable membrane.	Requires a semi-permeable membrane.

Transpiration and Evaporation

Transpiration	Evaporation
A physiological process occurring specifically in plants, involving the loss of water vapor from aerial parts, mainly through stomata.	A physical process involving the conversion of a liquid into a vapor, which can occur from any free surface (e.g., water bodies, soil, plant surfaces) and involves both living and non-living surfaces.
Regulated by stomatal opening and closing.	Primarily influenced by environmental factors like temperature, humidity, and wind.

Osmotic Pressure and Osmotic Potential

Osmotic Pressure	Osmotic Potential
The minimum pressure which needs to be applied to a solution to prevent the inward flow of its pure solvent across a semi-permeable membrane. It is a measure of the tendency of a solution to take up water by osmosis. It is always positive.	The potential energy of water per unit volume relative to pure water. It is the component of water potential due to dissolved solutes. It is always negative for solutions.
Osmotic Pressure = $\Psi_{s}$ (Osmotic Potential)	Osmotic Potential ( $\Psi_{s}$ ) = - (Osmotic Pressure)

Imbibition and Diffusion

Imbibition	Diffusion
The process by which a solid material (like a seed or cell wall) absorbs water and swells up. It involves the adsorption of water molecules onto the surface of the solid, followed by their diffusion into the solid structure. It is a special type of diffusion.	The general movement of any substance (solid, liquid, or gas) from a region of higher concentration to a region of lower concentration.
Requires a hydrophilic substance and water. Often leads to an increase in volume.	Does not require a specific hydrophilic substance; driven solely by concentration gradient.

Apoplast and Symplast pathways of movement of water in plants

Apoplast Pathway	Symplast Pathway
Movement of water through the non-living parts of the plant, i.e., through the cell walls and intercellular spaces. It is a continuous system but is bounded by the Casparian strip in the endodermis.	Movement of water through the living parts of the plant, i.e., from cytoplasm to cytoplasm via plasmodesmata connecting adjacent cells. It involves crossing cell membranes at least once.
Water moves passively, driven by mass flow.	Water movement can be passive or active, involving osmosis and movement through the interconnected cytoplasm.

Guttation and Transpiration

Guttation	Transpiration
The loss of water in the form of liquid droplets from the tips or margins of leaves, typically occurring when transpiration is reduced (e.g., at night or in high humidity) and root pressure is high. Occurs through specialized structures called hydathodes.	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 uptake and transport.
Loss of water as liquid.	Loss of water as vapor.
Occurs through hydathodes.	Occurs mainly through stomata.

Common mistakes

Confusing passive and active transport mechanisms.
Misunderstanding the conditions required for osmosis (semi-permeable membrane).
Difficulty in differentiating between similar physiological processes like transpiration and evaporation.
Incorrectly defining or comparing water potential and osmotic potential.

Revision tips

Focus on understanding the factors affecting diffusion and active transport.
Use the comparison tables in Question 5 to quickly revise differences between related terms.
Visualize the movement of water molecules to grasp the concept of water potential.
Practice explaining each transport mechanism in your own words.

Practice MCQs

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

Q2. What is the primary role of porins in plant cells?

Q3. Active transport in plants requires:

Q4. The water potential of pure water at standard temperature and pressure is defined as:

Q5. Which process involves the diffusion of a solvent 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 high concentration to an area of low concentration. Its rate is affected by the concentration gradient, the permeability of the membrane, temperature, and pressure.

How do protein pumps work in active transport?

Protein pumps are transmembrane proteins that bind to specific substances and use energy (from ATP) to move them across the membrane, often against the concentration gradient.

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 as a reference point. Any dissolved solute lowers the water potential, making it negative.

What is the key difference between diffusion and osmosis?

Diffusion is the general movement of particles down a concentration gradient, while osmosis is specifically the diffusion of water across a semi-permeable membrane.

What are porins and their function?

Porins are proteins that form large pores in the outer membranes of certain organelles and bacteria, facilitating the passive transport of small molecules.

How can these NCERT solutions help with exam revision?

These solutions provide clear, rewritten explanations for each question, breaking down complex topics and offering direct comparisons between similar processes, which is ideal for focused revision.

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