NCERT Solutions for Class 11 Biology Chapter 11 – Transport in Plants
Chapter 11 Transport in Plants is one of the most practically relevant chapters in Class 11 Biology, explaining the fundamental mechanisms by which plants absorb water, minerals, and nutrients — and distribute them across their entire body without a heart or circulatory system. Unlike animals, plants rely on physical and chemical gradients, specialized tissues, and membrane properties to move substances from roots to leaves and back. Must check the CBSE resources and NCERT Solutions.
For CBSE students and NEET aspirants, this chapter is a source of many conceptual and numerical questions, particularly around osmosis, water potential, transpiration pull, and the ascent of sap. The NCERT Solutions for Chapter 11 Transport in Plants available on Myclass24 provide clear, detailed, and exam-oriented answers to all textbook questions, helping students from cities like Lucknow, Patna, Jaipur, Pune, and across India build a solid understanding of this chapter quickly and effectively.
Download PDF – NCERT Solutions for Class 11 Biology Chapter 11 Transport in Plants
Plants need to transport water, minerals, organic nutrients, and signaling molecules between different parts — roots absorb water and minerals, leaves synthesize sugars, and both need to communicate. Unlike animals, plants have no active pumping organ, so transport depends on physical phenomena and specialized tissues.
There are two main pathways of transport in plants: short-distance transport (cell to cell) and long-distance transport (through vascular tissues). Short-distance transport includes diffusion, facilitated diffusion, active transport, and osmosis. Long-distance transport uses the xylem (for water and mineral salts from roots to shoots) and phloem (for food/sucrose from leaves to all other parts). Check out NCERT Solutions for Class 11 Biology and NCERT Solutions for Class 11 for the rest of the chapters.
Water potential (ψw) is a measure of the potential energy of water in a system relative to pure water. It determines the direction of water movement — water always moves from a region of higher water potential to lower water potential. Water potential is affected by solute concentration (ψs, solute potential — always negative) and pressure (ψp, pressure potential). In a turgid plant cell, pressure potential can be positive, balancing the negative solute potential.
| Term | Symbol | Definition | Value |
| Water potential | ψw | Total water potential of a system | ψw = ψs + ψp |
| Solute potential | ψs | Due to dissolved solutes | Always negative (≤ 0) |
| Pressure potential | ψp | Due to physical pressure | Can be +ve, -ve, or 0 |
| Pure water | — | Standard reference | ψw = 0 |
| Turgor cell | — | High ψp balances ψs | ψw approaches 0 |
| Plasmolyzed cell | — | ψp = 0 (no turgor) | ψw = ψs (very negative) |
Osmosis is the movement of water from a dilute solution (higher water potential) to a concentrated solution (lower water potential) across a semipermeable membrane. When a plant cell is placed in a hypotonic solution, water enters the cell causing it to become turgid. In a hypertonic solution, water leaves the cell and the cytoplasm shrinks away from the cell wall — a process called plasmolysis. The cell at which plasmolysis just begins is called the incipient plasmolysis.
The ascent of sap — the upward movement of water from roots to leaves — is explained by the Cohesion-Tension Theory proposed by Dixon and Joly. The driving force is transpiration pull (tension created in xylem due to water loss from leaves). This tension is transmitted down the continuous water column in xylem due to cohesion (hydrogen bonding between water molecules) and adhesion (attraction between water and xylem walls). The water column can withstand this tension because of the high cohesive strength of water.
Transpiration is the loss of water in the form of water vapor from aerial parts of the plant, primarily through stomata (stomatal transpiration — 80–90% of total transpiration). Factors that affect transpiration include temperature, humidity, wind speed, light, and CO₂ concentration. Transpiration serves multiple functions — it creates the pull for water movement, cools the plant, and helps distribute minerals.
| Type of Transpiration | Site | % of Total |
| Stomatal transpiration | Through stomata (leaves) | 80–90% |
| Cuticular transpiration | Through waxy cuticle | 5–10% |
| Lenticular transpiration | Through lenticels in stems | 0.1–0.2% |
Translocation of food in phloem follows the Pressure Flow Hypothesis (Mass Flow Theory) proposed by Ernst Munch. Sucrose produced in mesophyll cells (source) is actively loaded into phloem sieve tubes, increasing solute concentration and drawing water in by osmosis. This creates a high pressure at the source end. At the sink (roots, fruits, growing regions), sucrose is unloaded, reducing solute concentration and allowing water to leave — creating a pressure gradient that drives the flow from source to sink.
Mineral uptake by roots involves both passive (along concentration gradient) and active transport (against concentration gradient, using ATP via carrier proteins). Minerals like nitrate, phosphate, and potassium are absorbed actively. Once inside root cells, minerals move radially toward the xylem via the symplast (through cytoplasm and plasmodesmata) and apoplast (through cell walls and intercellular spaces) pathways. The Casparian strip in the endodermis blocks the apoplast route and ensures minerals pass through the symplast before entering xylem — a crucial quality control mechanism for the plant.
Myclass24 provides complete NCERT Solutions for Class 11 Biology Chapter 11 with diagram-based answers for topics like stomatal mechanism, osmosis, and phloem loading — essential for CBSE boards and NEET.