Transpiration |
Evaporation |
1. It is a physiological process and occurs in plants. 2. The water vapours diffuse through cucticle or through the stomata. 3. Living cells are involved. 4. Various forces such as vapour pressure, diffusion pressure, osmotic pressure, etc. are involved. 5. It is a slow process. 6. It is dependent upon anatomy of root, stem and leaves. |
1. It is a physical process and occurs on any free surface. 2. Any liquid can evaporate. The living epidemis and stomata are not required. 3. It can occur from both living and non-living surfaces. 4. No such forces are involved. 5. It is a fast process. 6. It is independent of anatomy of leaf, stem and roots. |
With the help of well-labelled diagrams, describe the process of plasmolysis in plants, giving appropriate examples.
When a cell is kept in a hypertonic solution, the concentration of the solution outside the cell is more. The concentration gradient makes the water from the cells moves out by the process of exosmosis. The water is lost from the cytoplasm and the vacuole. As the water is lost from the cell the cell membrane of the plant cells shrinks away from its cell wall. This condition of the cell is called as plasmolysed.
Factors affecting diffusion :
1. Temperature : The rate of diffusion is directly proportional to the temperature. As the temperature increases the rate of diffusion increases.
2. Surface area : More the surface area more will be the rate of diffusion.
3. Concentration gradient: The rate of diffusion is directly proportional to the concentration gradient.
4. Pressure - Increase in the pressure increase diffusion rate.
5. Permeability of the membrane separating the solutions. More permeable the mebrane more will be the diffusion.
(b) Explain what will happen to a plant cell if it is kept in a solution having higher water potential.
Transpiration | Guttation |
1. Water loss is in the form of water vapour. | 1. Water loss is in the form of water droplets. |
2. Occurs through stomata | 2. Occurs through hydathodes. |
3. Occurs usually during day | 3. Occurs during the night. |
4. Transpiration pull is involved | 4. Root pressure in involved |