Light Intensity
According to the Biology Edexcel specification, the rate of transpiration is affected by light intensity. In brighter light, there is more photosynthesis, which leads to more stomata opening to let in the required oxygen. As a result, more water can evaporate, leading to a higher rate of transpiration. During the night, when there is no photosynthesis, the stomata are closed, resulting in very little transpiration.
Temperature
The Biology Edexcel specification also states that temperature plays a role in the rate of transpiration. The warmer it is, the higher the rate of transpiration. This is because water particles have more energy and are more likely to evaporate and diffuse out of the stomata in one direction.
Humidity
Humidity, which refers to the amount of water vapor in the air, is another factor that affects the rate of transpiration. More humid air decreases the rate of transpiration because there is a large amount of water, which decreases the concentration gradient. As a result, less water will diffuse out, leading to decreased evaporation and an overall reduced rate of transpiration.
Air Flow
According to the Biology Edexcel specification, air flow, particularly high (windy) conditions, affects the rate of transpiration. In windy conditions, water molecules that leave the leaf are quickly blown away, leading to a high concentration gradient and an increased rate of transpiration. Additionally, more stomata are open for gaseous exchange in windy conditions, leading to more water evaporating and a steeper concentration gradient.
These factors, as outlined in the Biology Edexcel specification, all play a role in determining the rate of transpiration in plants. Understanding how light intensity, temperature, humidity, and air flow affect transpiration is essential for comprehending the processes of plant biology.
