factors affecting the rate of transpiration Flashcards
how does temperature affect the rate of reaction
more kinetic energy,more evaporation from mesophyll cells,more diffusion of water vapour through stomata.A higher air temperature can hold more moisture so it has a lower water potential making the gradient steeper.
how does humidity affect rate of reaction
air inside leaf is saturated, whereas external air has lower water potential.
Increases in external humidity would lower the gradient
how doe air movement affect rate of reaction
wind removes layer of saturated air just outside the stomata which reduces the water potential so the water potential gradient is steeper,therefore transpiration increases
how does light intensity affect rate of transpiration
light opens the stomata so transpiration increases
what is a potometre
a device used to measure water uptake by roots
how does a potometre measure transpiration
transpiration is near impossible to measure so as water uptake is proportional to transpiration,this is used to indicate the rate of transpiration
what is water uptake proportional to
transpiration
what is transpiration
Transpiration is a process that involves loss of water vapour through the stomata of plants. The loss of water vapour from the plant cools the plant down when the weather is very hot, and water from the stem and roots moves upwards or is ‘pulled’ into the leaves.
what is the first step in using a potometre
a sample of plant musr be cut from a plant underwater,this is to prevent any air from entering the xylem and breaking the water column
what is the second step to using a potometre
the potometre is then filled with b water and all air bubbles are removed
what is the third step to using a potometre
the cut leafy plant is then attached to the potometre , using rubber seals and petroleum jelly to make the equipment air tight
what is the last step (fourth) to using a potometre
one air bubble is then introduced into the equipment and the distance that this air bubble has moved towards the plant is recorded
how do you convert distamce of bubble movement into an estimate of transpiration
rate the distamce the bubble moved can be used to work out the volume of water in the tube that evaporated
how is the volume of water in the tube evaporated recorded
this volume is divided by the time it took to loose that volume of water to get a rate
this apparatus can be reset with different conditions applied to see if the rate changes ,what are some examples
a lamp could replicate sunlight
a fan may be applied to replicate wind
or a plastic bag over the plant to increase humidity
why must the apparatus be set up and the plant shoot be cut under water
due to the cohesion tension theory,creating a negative pressure in the xylem,this would break the continuous flow of water and water column and prevent transpiration,cutting underwater means only water is drawn to the xylem
in which part of the potometre do you find a bubble?
the capillary tube
what do you use to measure the distance the air bubble moves
a ruler
if you increase the temperature the rate of transpiration will_______
increase
if the air bubble moves further there is?
an increased rate of transpiration
