Explain the effects on the rate of transpiration of varying the following factors: temperature, wind speed and humidity

The rate of transpiration in plants is significantly influenced by environmental factors such as temperature, wind speed, and humidity. Here’s how each of these factors affects transpiration:

1. Temperature

• Effect on Transpiration Rate: As temperature increases, the rate of transpiration also increases.
• Explanation:
  • Kinetic Energy: Higher temperatures provide water molecules with more kinetic energy, which increases the rate of evaporation from the surfaces of mesophyll cells into the air spaces within the leaf.
  • Diffusion Gradient: Warm air can hold more water vapor, which enhances the concentration gradient between the inside of the leaf (high water vapor concentration) and the outside atmosphere (lower water vapor concentration). This gradient promotes faster diffusion of water vapor out of the stomata.
  • Stomatal Opening: Increased temperatures often lead to stomatal opening for gas exchange during photosynthesis, further facilitating water loss through transpiration. However, if temperatures become excessively high, plants may close their stomata to conserve water, which can reduce transpiration rates.

2. Wind Speed

• Effect on Transpiration Rate: As wind speed increases, the rate of transpiration also increases.
• Explanation:
  • Removal of Water Vapor: Wind removes water vapor that accumulates around the leaf surface. This rapid removal maintains a steep concentration gradient for water vapor between the inside of the leaf and the outside air, allowing more water to diffuse out through the stomata.
  • Increased Evaporation: Wind enhances evaporation from leaf surfaces by replacing humid air with drier air, which encourages further water loss. On still days, humid air can build up around leaves, slowing down transpiration.

3. Humidity

• Effect on Transpiration Rate: As humidity increases, the rate of transpiration decreases.
• Explanation:
  • Saturation of Air: High humidity means that the air contains a high concentration of water vapor. When the surrounding air is saturated with moisture, there is less of a concentration gradient for water vapor to diffuse out of the leaf.
  • Reduced Driving Force: With less difference in water vapor concentration between the inside of the leaf and the outside atmosphere, fewer water molecules will diffuse out through stomata. Conversely, when humidity is low (dry conditions), there is a greater driving force for transpiration as more water vapor can escape into drier air.