Mass Transport- Xylem Flashcards
What doe the xylem tissue transport?
Water and mineral ions
What are xylem vessels?
Very long tube-like structures formed from dead cells (vessel elements) joined end to end, have no end walls so water can pass easily
Where does water evaporate from?
The leaves, causes tension
What does it mean that water molecules are cohesive?
They stick together so creates column of water from leaves to roots moving upwards
Where does water enter the stem?
Through the roots
What is transpiration?
The evaporation of water from a plant’s surface
What happens during transpiration?
- Water evaporates from moist cell walls and accumulates in spaces between cells in the leaf
- When stomata open, moves out the leaf down the concentration gradient
How does light affect transpiration rate?
Lighter it is means faster transpiration rate because stomata open when it gets light to let in carbon dioxide for photosynthesis
How does temperature affect the rate of transpiration?
Higher temperature means faster transpiration rate as warmer water molecules have more energy so evaporate from cells faster which increases concentration gradient which makes water diffuse out the leaf faster
How does humidity affect the rate of transpiration?
Lower humidity means faster transpiration rate because if air around plant is dry then concentration gradient is increased
How does wind affect transpiration rate?
Windier it is means faster transpiration rate as lots of air blows away water molecules which increases concentration gradient
How do you dissect plants to look at the xylem and phloem in plant tissue under a microscope?
- Use a scalpel to cut a cross-section of the stem as thinly as possible
- Use tweezers to place cross-sections in water to prevent them from drying out
- Transfer each section to a dish containing a stain (toluidine blue) and leave for 1 minute- this stains lignin of xylem vessels blue-green
- Rinse of sections and mount onto slide
