required practical- potometer Flashcards
what does a potometer do
estimates the rate of transpiration by measuring the rate of water uptake by a leafy shoot
why are potometers an estimation not a measurement
because some water taken by the shoot isn’t just used by transpiration, it is also used by photosynthesis.
it could also be used to maintain turgor pressure
what is important about the plant when conducting the potometer experiment
needs to be a healthy shoot
leaves need to be dry for a high water vapour potential gradient
why do we need to submerge the apparatus underwater
to avoid water bubbles getting into apparatus
why do we have to cut the shoot underwater
avoids air entering xylem interrupting transpiration
why do you have to cut the shoot at an angle
provide a large surface area in contact with the water
a reservoir is a component of the apparatus of a potometer- what does it do
a resevoir resets air bubbles position
what replaces water lost by transpiration of the healthy shoot
water from the capillary tube replaces water lost
what does the distance of the air bubble indicate for the shoot
the distance travelled by the air bubble can be used to calculate volume of water taken up by the plant.
questions may ask for the volume of the capillary tube which is a cylinder shape, what equation calculates the volume of a cylinder
pie x r2 x d
what can be used to ensure an air tight seal of the potometer and the shoot
tape
vaseline
can be used to create a seal and prevent leaks in apparatus
what can be added to the water to make the air bubble more visible
colouring to the water
what is the equation for the rate of transpiration
rate = distance travelled by air bubble / time
what are limitations of the potometer experiment
cut shoot isn’t active for long
photosynthesis and turgor pressure uses up water too
hard to set up without air bubbles in apparatus
