The loss of excess water in the form of vapor through the aerial parts of a plant is called transpiration.

Transpiration
Transpiration is the process by which excess water in the form of vapor is lost through the aerial parts of a plant, mainly through the stomata on the leaves. This process is crucial for plants as it helps in cooling the plant, transporting nutrients and minerals, and maintaining turgidity in the cells.
Significance of Transpiration
- **Cooling mechanism**: Transpiration helps in cooling the plant by releasing excess heat during the process of water vaporization.
- **Nutrient transport**: Water and minerals absorbed by the roots are transported to different parts of the plant through the process of transpiration.
- **Maintaining turgidity**: Transpiration helps in maintaining turgidity in the plant cells, which is essential for plant structure and growth.
Mechanism of Transpiration
- **Stomata**: Tiny openings on the surface of leaves through which water vapor escapes.
- **Guard cells**: Surround the stomata and regulate their opening and closing to control transpiration.
- **Root pressure and cohesion-tension theory**: Water is absorbed by roots and transported to leaves, where it evaporates through stomata due to differences in water potential.
Factors affecting Transpiration
- **Environmental conditions**: Temperature, humidity, wind speed, and light intensity influence the rate of transpiration.
- **Plant factors**: Number and distribution of stomata, leaf surface area, and plant species affect transpiration rates.
Conclusion
Transpiration is a vital process for plants as it helps in maintaining water balance, nutrient transport, and overall plant health. Understanding the mechanisms and factors influencing transpiration is crucial for effective plant growth and development.