Describe transpiration as the loss of water vapour from leaves

Sourav PanNovember 14, 2024

Answered step-by-step

Transpiration is a vital physiological process in plants that involves the loss of water vapor from aerial parts, primarily through small openings called stomata located on the surfaces of leaves. This process plays a crucial role in maintaining plant health and facilitating various functions. Here’s a detailed description of transpiration:

Definition of Transpiration

Transpiration is the process by which water vapor is lost from the internal tissues of a plant to the atmosphere. It primarily occurs through stomata, which are tiny pores on the leaf surface, but can also happen through cuticles and lenticels.

Mechanism of Transpiration

1. Water Uptake:
   • Water is absorbed by the roots from the soil and transported through the plant via xylem vessels. This water moves up to the leaves where it enters mesophyll cells.
2. Evaporation:
   • Within the leaf, water molecules evaporate from the surface of mesophyll cells into the air spaces inside the leaf. This creates a higher concentration of water vapor inside the leaf compared to the outside atmosphere.
3. Diffusion:
   • The water vapor then diffuses out of the leaf through stomata into the surrounding air. The rate of diffusion is influenced by factors such as humidity, temperature, and wind speed.

Factors Affecting Transpiration

• Stomatal Regulation: Plants can regulate transpiration by opening or closing their stomata in response to environmental conditions. For example, stomata may close during high temperatures or drought conditions to reduce water loss.
• Environmental Conditions:
  • Humidity: Lower humidity levels increase the rate of transpiration since there is a greater gradient for water vapor to diffuse out.
  • Temperature: Higher temperatures increase evaporation rates, leading to higher transpiration rates.
  • Wind Speed: Increased air movement can enhance transpiration by removing water vapor from around the leaf surface, maintaining a steep concentration gradient.

Importance of Transpiration

1. Cooling Effect: Transpiration helps cool plants, particularly during hot weather, as evaporating water absorbs heat from leaf surfaces.
2. Nutrient Transport: The loss of water through transpiration creates a negative pressure in xylem vessels, which aids in pulling water and dissolved nutrients upward from roots to leaves (the transpiration stream).
3. Water Regulation: Transpiration plays a role in regulating water balance within plants, helping maintain turgor pressure necessary for structural integrity and growth.
4. Photosynthesis: By facilitating gas exchange (CO₂ intake and O₂ release) through stomata during transpiration, this process supports photosynthesis.