Transpiration - Transpiration in Plants (GCSE Biology)
Transpiration in Plants
Transpiration Stream
Transpiration
- Transpiration is the evaporation and movement of water away from the plant’s leaves from the inside of the plant. Transpiration occurs as water diffuses through the plant from the roots and evaporates from the leaves through the stomata openings (more on this later). The evaporation of water from the leaves causes a shortage of water in the plant, allowing more water to be taken up from the roots. Water then moves through the transpiration stream in the plant.
- Water moves through the transpiration stream. Water moves through the xylem as part of the transpiration stream. The pathway of water is through the root hair cells, root cortex cells and then to the xylem which transports water to the mesophyll cells in the leaves.
- The transpiration pull moves water up and drags other water molecules up too due to cohesion. Water molecules stick to each other (cohesion) and pull water molecules below it through the entire xylem.
- You can investigate the movement of water using a stain. Place a plant stem in water dyed with a stain. The coloured water will travel up the xylem and stain the stem and even the veins in the leaves of the
plant.
Factors Affecting Transpiration
- Transpiration is affected by temperature. As temperature increases, so does the rate of transpiration as the water particles gain more energy to diffuse into the plant evaporate out of the stomata.
- Transpiration is affected by humidity. When the air is more humid, the concentration gradient is reduced. This means that the rate of diffusion is lowered and so the transpiration rate is reduced.
- Transpiration is affected by air movement. As the movement of air increases, the concentration gradient is increased, so the rate of transpiration increases.
- Transpiration is affected by light intensity. As the light intensity decreases, the stomata close up and there is a reduction in photosynthesis. This means that very little water can escape and so the rate of transpiration decreases.
Transpiration is the process of water movement through a plant and its evaporation from aerial parts, primarily from the leaves but also from stems and flowers.
Transpiration helps to transport water and minerals from the roots to the leaves, regulate the plant’s temperature, and maintain turgor pressure in the cells.
Transpiration starts at the roots, where water is absorbed and transported to the leaves through the xylem. In the leaves, water evaporates from the stomata, which are tiny pores on the surface of the leaves. This evaporation creates a pull, or a “suction force,” that draws more water up the plant.
Several factors can affect the rate of transpiration in plants, including humidity, temperature, light, wind, and the opening and closing of the stomata.
Transpiration is an important part of the water cycle because it helps to redistribute water from the Earth’s surface back into the atmosphere, where it can form clouds and eventually return as precipitation.
Transpiration and photosynthesis are closely related because both processes occur in the leaves of plants. During photosynthesis, plants take in carbon dioxide and use energy from light to produce sugar and oxygen. The water absorbed by the roots helps to cool the leaves and maintain the conditions needed for photosynthesis to take place.
Yes, transpiration can be measured by placing a potometer, which is a device that measures the rate of water uptake in a plant, on a stem or leaf. This can give us an idea of how much water the plant is losing through transpiration.
Stomata play a crucial role in transpiration because they are the primary sites where water vapor is released from the plant. The opening and closing of the stomata regulates the rate of transpiration, allowing the plant to conserve water when necessary.
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