Transpiration

Transpiration is the process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere. Transpiration is essentially evaporation of water from plant leaves.

Mechanism of Transpiration:

Transpiration occurs through stomata, which are tiny openings on the surface of leaves. Water is absorbed by the roots from the soil and transported to the leaves through the xylem vessels. Once in the leaves, water evaporates from the moist cell walls into the air spaces of the leaf. This water vapor then diffuses out of the leaf through the stomata into the surrounding air.

Factors Affecting Transpiration:

1. Temperature: Higher temperatures increase the rate of transpiration as the water evaporates more quickly.
2. Humidity: Lower humidity levels outside the leaf lead to a higher rate of transpiration, as the concentration gradient favors the movement of water vapor out of the leaf.
3. Wind: Increased air movement removes water vapor from around the leaf, maintaining a lower concentration of water vapor outside the leaf, which increases transpiration.
4. Light: Intense light can cause stomata to open wider, increasing transpiration rates.

Role of Transpiration:

Transpiration is important for the following reasons:

• It helps in the absorption and transport of water and minerals from the roots to the shoots and leaves.
• It cools the plant as water evaporates from the surface of the leaves, similar to how sweating cools humans.
• It maintains the turgidity of the plant, ensuring that the cells remain firm and the plant remains upright.
• It assists in the movement of nutrients and water through the xylem.

Study Guide:

To understand transpiration better, it's important to review the following concepts:

1. The structure of stomata and their role in transpiration.
2. The cohesion-tension theory and its role in pulling water up from the roots to the leaves.
3. The factors that influence the rate of transpiration and how they affect the process.
4. The significance of transpiration in the overall functioning of plants.

It may also be helpful to perform experiments to observe and measure transpiration rates under different conditions, such as varying temperature, humidity, and light intensity.