September 29, 2025

What Is Transpiration

Q: What part of the plant controls transpiration?

Transpiration is primarily controlled by the stomata, which are tiny pores on the leaf's surface. Each stoma is surrounded by two guard cells that can open or close the pore to regulate water loss and gas exchange.

Q: How do environmental factors affect transpiration?

Factors like light, temperature, humidity, and wind all affect the rate of transpiration. Higher temperatures, more light, and increased wind speed generally increase transpiration, while high humidity decreases it.

Q: Is transpiration the same as evaporation?

No. While transpiration involves the evaporation of water from the plant's surface, it is a specific physiological process of living plants. Evaporation is a general physical process where a liquid turns into a gas from any surface, such as a lake or wet soil.

Q: Do all plants transpire?

Yes, virtually all vascular plants transpire, but the rate varies significantly. Plants in arid environments, like cacti, have evolved special adaptations such as fewer stomata, thick waxy cuticles, or CAM photosynthesis to minimize water loss through transpiration.

Learn about transpiration, the process by which plants release water vapor from their leaves, and understand its vital role in plant survival and the water cycle.

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Defining Transpiration in Plants

Transpiration is the biological process where plants absorb water through their roots and then release it as water vapor from pores in their leaves, called stomata. It is often described as the plant equivalent of sweating and is a key part of the water cycle.

Section 2: The Mechanism of Transpiration

The process is driven by evaporation from the leaf surface. As water evaporates, it creates a negative pressure, or tension, in the plant's xylem (water-conducting tissues). This tension pulls more water up from the roots through the stem to replace what was lost, creating a continuous flow called the transpiration stream.

Section 3: A Practical Example

Consider a large sunflower in a garden on a hot, sunny day. It absorbs water from the soil through its roots. This water travels up the stalk to the leaves and flowers. The majority of this water is then released into the air as invisible water vapor through the stomata on the underside of its leaves, helping to cool the plant.

Section 4: Importance of Transpiration

Transpiration is crucial for two main reasons. Firstly, it facilitates the transport of essential minerals and nutrients dissolved in the water from the soil to all parts of the plant. Secondly, the evaporation of water has a cooling effect, which protects the plant's leaves from overheating in direct sunlight.

Frequently Asked Questions

What part of the plant controls transpiration?

How do environmental factors affect transpiration?

Is transpiration the same as evaporation?

Do all plants transpire?