Transport in Plants Flashcards
Xylem vessels
transport water and minerals from the roots to the stem and leaves
Phloem vessels
transport food materials (mainly sucrose and amino acids) made by the plant from photosynthesising leaves to non-photosynthesising regions in the roots and stem
Adaptations of the xylem
Cells joined end to end with no cross walls to form a long continuous tube; Cells are essentially dead, without cell contents, to allow free passage of water;Outer walls are thickened with a substance called lignin, strengthening the tubes, which helps support the plant
What are root hairs?
Single-celled extensions of epidermis cells in the root that grow between soil particles and absorb water and minerals from the soil
Why is having a large surface area important for the root hair cells?
Increases the rate of the absorption of water by osmosis and mineral ions by active transport
What is the passage of water in a plant?
Water moves by osmosis from the root hair cells into the root cortex, into the xylem vessels and into the mesophyll cells
What is transpiration?
The loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by diffusion of water vapour through the stomata
What are the functions of transpiration?
Transporting mineral ions; providing water to keep cells turgid in order to support the structure of the plant
providing water to leaf cells for photosynthesis; keeping the leaves cool (the conversion of water (liquid) into water vapour (gas) as it leaves the cells and enters the airspace requires heat energy (the using up of heat to convert water into water vapour helps to cool the plant down)
How does transpiration work?
Water molecules are attracted to each other by cohesion - creating a continuous column of water up the plant. Transpiration produces a tension or ‘pull’ on the water in the xylem.
What factors affect the rate of transpiration?
Wind speed, Humidity, Light intensity, and Temperature
How does light intensity affect the rate of transpiration?
The higher the light intensity is, the faster transpiration would occur. When there is more light the stomata is open in order to allow carbon dioxide to enter and be used in photosynthesis. Therefore, more water can evaporate.
How does temperature affect the rate of transpiration?
The higher the temperature, the faster transpiration would occur. This is because the particles have more kinetic energy and water molecules evaporate from the mesophyll and diffuse away. faster.
How does wind speed/air movement affect the rate of transpiration?
Good airflow removes water vapour from the air surrounding the leaf which sets up a concentration gradient between the leaf and the air, increasing water loss.
How does humidity affect the rate of transpiration?
The drier the environment the faster the rate of transpiration. This is because when air is saturated with water vapour the concentration gradient is weaker so more water is lost.
What is a potometer?
A piece of equipment used to investigate the rate of transpiration. (know how to explain the method) https://www.youtube.com/watch?v=cJrSa8sfd7A
