transpration

Question 1

what is transpiration?

Answer 1

evaporation of water from aerial parts of plants, especially leaves.

Question 2

why does transpiration happen?

Answer 2

Stomata open so they can absorb CO2 for photosynthesis.
This provides a pathway for water loss through the open stomata.
Water vapour moves down a water potential gradient from the air spaces in the leaf into the atmosphere.
so it is a side effect of gas exchange

Question 3

what are the 4 factors effecting transpiration rate

Answer 3

light intensity, temperature, humidity, and wind speed.

Question 4

how does light intensity effect transpiration

Answer 4

At high light intensities, stomata open for maximum CO2 absorption for photosynthesis, increasing the transpiration rate.

Question 5

how does humidity effect transpiration?

Answer 5

Low humidity increases the water vapour gradient between the leaf and atmosphere, increasing the transpiration rate.

Question 6

how does temprature effect transpiration?

Answer 6

At high temperatures, evaporation of water molecules is faster due to higher kinetic energy, increasing the transpiration rate.

Question 7

how does wind speed effect transpiration?

Answer 7

High wind speeds increase the water vapour gradient between the leaf and atmosphere, increasing the transpiration rate.

Question 8

what is a potometer used for?

Answer 8

used to measure the rate of transpiration.

Question 9

what are the steps in using a potometer?

Answer 9

1.Cut the shoot underwater at slant to increase the surface area for water uptake.
2.Assemble the potometer with the shoot submerged in water.
3.Keep the capillary tube end of the potometer submerged throughout the experiment.
4.Check that the apparatus is airtight.
5.Dry the leaves, and give the shoot time to acclimatise.
6.Shut the tap, form an air bubble and record its position.
6.Measure the distance the air bubble moves and the time taken.
7.Change one variable at a time and keep everything else constant.

Question 10

what do u need to calculate before calculation the rate of transpiration?

Answer 10

we first need to calculate the volume of water that has been taken up by the plant to estimate how much has been lost from the plant over this time period

Question 11

how do u calculate rate of transpiration?

Answer 11

Calculate the cross-sectional area of the capillary tube (this is the area of the circle that forms a cross section of the tube): SA of a circle= pi R^2

Calculate the volume of water uptake by multiplying the value from step 1 by the distance the air bubble travelled, ‘d’ (that is, calculate the area of the cylinder of water that has been taken up by the plant): pi r^2 X d

Calculate the rate of water uptake (an estimate for the rate of transpiration) by dividing the value calculated in step 2 by the time taken:
rate of transpiration=
volume of water uptake/ time taken