Back to: Botany 200 Level
Hello, my brilliant student! How are you doing today? Have you ever noticed how clothes dry faster when the sun is out or when it’s windy? The same happens to plants! The rate at which they lose water through transpiration depends on different environmental factors. Today, we’ll learn about the key factors that affect transpiration and how they influence the amount of water a plant loses.
Factors affecting transpiration (light, temperature, humidity, wind)
Transpiration is the loss of water vapour from plant leaves through the stomata. Several factors determine how fast or slow this process happens. The four most important ones are light, temperature, humidity, and wind.
1. Light – The More Light, The More Transpiration
Plants open their stomata to take in carbon dioxide (CO₂) for photosynthesis, which mostly happens during the day when there is light. Since the stomata are open, water also escapes, increasing transpiration.
Effect of Light:
Bright light → More stomata open → Increased transpiration.
Dim light or darkness → Stomata close → Reduced transpiration.
Example: Imagine running around in the sun—you sweat more because your body needs to cool down. Similarly, plants transpire more in bright light.
2. Temperature – Heat Increases Water Loss
As temperature increases, water evaporates faster from the leaf surface, making transpiration occur more quickly.
Effect of Temperature:
High temperature → Faster evaporation → Increased transpiration.
Low temperature → Slower evaporation → Reduced transpiration.
Example: Just like how wet clothes dry faster on a hot day, plants lose more water when it’s hot. That’s why some plants wilt during the afternoon heat.
3. Humidity – More Moisture in the Air, Less Transpiration
Humidity refers to the amount of water vapour in the air. If the air is already full of moisture, water from the plant does not evaporate easily. But if the air is dry, water evaporates quickly, increasing transpiration.
Effect of Humidity:
High humidity (moist air) → Slower transpiration.
Low humidity (dry air) → Faster transpiration.
Example: Think about how quickly sweat dries on a dry, breezy day compared to a humid, sticky day. Similarly, plants lose more water in dry air.
4. Wind – The Windier, The More Transpiration
Wind removes water vapour from around the leaf surface, making room for more evaporation. The stronger the wind, the faster this happens.
Effect of Wind:
Strong wind → More water vapour removed → Faster transpiration.
No wind → Water vapour stays around the leaves → Slower transpiration.
Example: Imagine hanging wet clothes outside. If the wind is strong, they dry much faster. In the same way, wind increases transpiration in plants.
Summary
Transpiration is affected by four major factors:
Light – More light means more stomata open, increasing transpiration.
Temperature – Higher temperatures increase water evaporation and transpiration.
Humidity – High humidity slows down transpiration, while dry air speeds it up.
Wind – Strong wind removes water vapour, increasing transpiration.
Evaluation
- Why does transpiration increase when light intensity is high?
- How does temperature affect the rate of transpiration?
- Why do plants lose less water when the air is humid?
- What effect does strong wind have on transpiration?
Great job today! Now you know why plants behave differently under different weather conditions. Keep up your curiosity—Afrilearn is here to make your learning journey exciting and easy. See you in the next lesson!
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