Transport in Plants Flashcards
Why do plants require a transport system?
To ensure all cells receive a strong supply of nutrients they require. Especially important as a plant must be able to transport substances up their stem (against gravity)
What is a Xylem cells structure?
Long, continuous columns made up fo dead tissue, allowing transportation of water.
Contains pores, allowing water to move sideways between vessels.
Thickened with a tough substance, providing structural support.
What is the structure of phloem cells?
Sieve tube elements transport sugars around the plant.
Companion cells designed for active transport for sugars into tubes.
Plasmodesmata allow flow of substances between cytoplasm of different cells.
What is transpiration?
The evaporation of water from the leaves of a plant.
Consequences of gaseous exchange; occurs when the plant opens the stomata to exchange oxygen and CO2
What affects the rate of transpiration?
Increased light increases transpiration.
Increased temperature increases transpiration.
Increasing humidity decreases transpiration.
Waxy cuticle prevents transpiration
How can you measure transpiration rate?
Potometer. Plant cutting is placed in a water-filled tube that contains an air bubble. Rate of transpiration is calculated by measuring the movement of the air bubble over time.
What is water potential?
The tendency of water to move by osmosis, from high water potential to low. Pure distilled water has the highest water potential of 0. This is the basis by which water moves to the areas it is needed within the plants.
What is the apoplastic pathway?
A method of osmosis through the root hair cells, where the water moves theough the cell walls and intercellular spaces. This pathway can only be used until water reaches the Casparian Strip.
What is the Symplastic Pathway?
A method of osmosis through the root hair cells, where water moves through the cytoplasm via plasmodesmata. To begin this pathway, water must be actively transported into the cells.
What are the adaptations of xerophytes?
Small/rolled leaves Densely packed mesophyll Thick waxy cuticle Stomata often closed Hairs trap moist air
What are the adaptations of hydrophytes?
Thin or absent waxy cuticle
Stomata are often open
Wide, flat leaves
Air spaces for buoyancy
What is translocation?
Sucrose produced in leaves loaded into sieve tubes via active transport.
Lower water potential causing water to move in from the xylem.
Assimilates move along the sieve tube towards areas of lower hydrostatic pressure. Sucrose diffuses into the surrounding cells where it is needed.
