transpiration and translocation SB6 Flashcards
what is transpiration?
The flow of water into a root up the stem and out of the leaves
what are xylem vessels?
what are inside them?
tiny continuous pipes leading from a plants roots up into its leaves- inside is a continuous chain of water due to weak forces of attraction between water molecules.
what can be used to investigate the factors affecting transpiration?
potometer
do water molecules diffue down or up the concentration gradient outside of the leaf - why?
down- the concentration of the water vapour in the air spaces inside a leaf is greater than outside it
what factors affect transpiration?
wind, low humidity, higher temps, greater light intensity
factors that reduce the concentration of water molecules outside the stomata will increase what?
transpiration
what happens furing their development?
they die and their top and bottom walls disintergrate and so this forms long empty vessels through which water can easily move
what are the properties of xylem? - what creates this?
They are rigid due to their thick walls and rings of hard lignin
what does the rigidness of the xylem help the plant to do?
- water pressure inside the vessel does not burst
- support the plants
what is translocation?
the transport of sugars and minerals through the plant
what is phloem
vascular tissue that transports food substances produces by photosynthesis
what is the phloem composed of?
sieve tubes and companion cells
how does sucrose move through the phloem?
sucrose is translocated in the seive tubes of the phloem tissue - the central channel in each sieve cell is connected to its neighbour by holes which the sucrose flows through. As sucrose is pumped into sieve tubes - the increased pressure causes sucrose to flow up to growing shoots or storage organs
what do companion cells do?
activeley pump sucrose into/out the sieve cells that form the sieve tubes.
