plant mass transport-xylem and phloem Flashcards
what is the function of xylem tissue
xylem tissue transports
water and mineral ions in solution
these substances move up the plant from the roots to the leaves
what is the function of phloem tissue
phloem tissue transports
organic substances like sugars
both up and down the plant
outline the cohesion tension theory of water transport in xylem
water evaporates from leaves at the top of the xylem
creating tension pulling more water into leaf
water molecules cohesive so when some pulled into leaf others follow
meaning whole column of water in the xylem from leaves down to the roots moves up
water then enters the stem through the roots
what is transpiration
evaporation of water from a plant’s surface water vapour potential gradient
name 4 factors that affect rate of transpiration
light intensity
temperature
humidity
wind
how does light intensity affect the rate of transpiration
as stomata open when it is light
to let in CO2 for photosynthesis
when it is dark the stomata
are shut so there is little transpiriation
how does temperature affect rate of transpiration
as temperature increases
more water evaporates
increasing water vapour potential gradient
between the leaf and air so transpiration rate increases
how does humidity affect the rate of transpiration
if humidity is low
the water potential gradient
between the leaf and the air increases
so transpiration rate increases
how does wind affect the rate of transpiration
the wind blows away water molecules from around the stomata
this increases the water potential gradient
increasing transpiration rate
name 4 pieces of evidence for mass flow
metabollic inhibitors
pressure using aphids
radioactive tracers
ringing experiments
explain how ringing experiments provide evidence for mass flow
if ring of bark is removed from woody stem
bulge forms above above the ring
fluid from bulge higher concentration of sugars
than fluid below the bulge
as sugars can’t move past the area where bark has been removed
explain how pressure using aphids provides evidence for mass flow
sap flows out quicker nearever leaves than further down the stem
showing that there is a pressure gradient
how can a radioactive tracer be used to provide evidence for mass flow
radioactive C14 in CO2 is incorporated into organic substances by photosynthesis which will then be moved around plant by translocation
explain how metabollic inhibitors can provide evidence for mass flow
ATP production stops
translocation stops
this is evidence that there is active transport involved
