Transportation is the process of movement of water and minerals to all parts of the plant body. Plants have a specialized system that enables them to distribute water and nutrients throughout their body. They use several processes such as translocation, absorption, storage and utilization of water.
Note: As per the revised CBSE curriculum, the complete chapter has been removed from the syllabus for the 2020-21 academic session.
Let us have a look at the different processes of transport in plants.
|NCERT Solutions for class 11 Biology Chapter 11|
|NCERT Exemplar for class 11 Biology Chapter 11|
Transport in plants takes place through different mechanisms:
In this system, the molecules move from a region of higher concentration to a region of lower concentration. This process requires no energy.
Here, the system moves molecules from a region of higher concentration to a region of lower concentration with the help of a carrier, usually a protein. This process does not require any energy and hence is known as the passive process.
This mechanism transfers molecules from a region of lower to a region of higher concentration with the help of membrane proteins. This system is termed as active transport because it requires ATP to function.
Water potential is used by the plants to transport water to the leaves that help in carrying out photosynthesis. Solute potential and pressure potential are the two main components of water potential.
Solute potential is also known as osmotic potential and is negative in the plant cell. Pressure potential is positive in the plant cell. Higher the concentration of water in the system, greater will be the water potential.
Osmosis is the movement of molecules from a region of higher concentration to a region of lower concentration across a semi-permeable membrane until an equilibrium is reached.
The plant cell wall is freely permeable to substances in solution and water. Osmosis is of two types:
- Endosmosis: This is the movement of water molecules enters into the cell when the cell is placed in a hypotonic solution.
- Exosmosis: This is the movement of water molecules out of the cell when the cell is placed in a hypertonic solution.
Plasmolysis is the process in which plant cell loses water when placed in a hypertonic solution. It depends upon three types of solutions:
- Isotonic: This refers to two solutions with the same osmotic pressure across the semi-permeable membrane.
- Hypotonic: This is the solution which has a lower osmotic pressure than another solution.
- Hypertonic: This is the solution with higher osmotic pressure than another solution.
The cells when placed in a hypotonic solution swell or get deplasmolysed. Whereas, the cells when placed in a hypertonic solution shrink or get plasmolysed.
Imbibition is the process of adsorption of water by solids called colloids. This results in an increase in the volume. For eg., adsorption of water by seeds.
Transpiration is the removal of excess water from the aerial parts of the plants. It mainly occurs through the stomata of the leaves. It is influenced by light, temperature, wind and humidity.
Xylem helps in the movement of water from roots to the leaf veins. The phloem helps in the movement of food prepared by the leaves to various parts of the plants.
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Transport in Plants Class 11 – Important Questions
- Name the factors that affect the rate of diffusion.
- Define porins.
- What is the difference between osmosis and diffusion?
- What is root pressure and how does it help in the movement of water in the plant?
- Why do guards cells that are found in the stomata open and close during transpiration?
- Define water potential.