Transpiration in plants

Here is close up of stomata

Preliminary experiment

We also did a preliminary experiment to help us make a prediction of what will happen in my experiment. Here's what we did.

3 plants were each separately placed in 3 flasks with the same amount of water in them. To keep the water from evaporating we put oil in the water, as oil is non-permeable. We then marked the water level.

The 3 plants were in different conditions. The first had a layer of vaseline applied to the upper part of the leaves; the second had a layer of vaseline on the bottom. The third was left as normal with no alterations. We then measured it's mass and then after we a day we measured the mass again. We then topped up the flasks with water.

I make a prediction that plant 1 will have a mass gain because it will be able to photosynthesis. I think that plant 2 will change its mass but only a little bit after top up as the vaseline might stop photosynthesis. Plant 3 will hold in the water because the vaseline will stop the guard cells from releasing any unused water so therefore the cells would become turgid making the mass change. Here are the results of that experiment.

Because the water level went down after 1 day, this proves that plants take in water. However the experiment did not go quite as planned as none of the plants increased their mass at all. This could have been for many reasons. The third plant should have been heavier as the stomata wouldn't be able to release its water.

Factors that could have affected this test

• Wind
• Temperature
• The number of leaves on the plant
• The surface area of the roots

However we did gain some conclusions from this test.

Conclusions

• The plants take in water.
• If transpiration stops, the water level stays the same.
• The third plant didn't take in water because the stomata were blocked.

Main Experiment

My aim

The aim of this project is to discover how certain conditions can affect transpiration in plants.

Equipment list

A plant with exactly 24 leaves on it.

Two clamps, to hold the plant up.

A glass tube, to put water in

A ruler, to measure air bubbles.

A beaker full of water, for the plant to get used to the conditions.

A black bag, for our 3rd experiment to cover it up.

Rubber tubing, so that the stem is sealed tightly.

A piece of filter paper

Stopwatch

A stand

Method

First of all we fill the glass tube with water, the rubber tubing is place on the end of the pipette, there can't be any air bubbles in the tube. We then push the plant into the rubber tubing, again making sure there aren't any air bubbles. We then clamp the plant horizontally with the end of the tube in the beaker of water, leave it for 10 minutes so that the plant has time to adjust to it's new conditions then start the experiment. So we take the end of the tube out of the beaker and make an air bubble by putting the piece of filter paper underneath the end of the pipit, this creates an air bubble. We mark the top of the air bubble and then start the timer. At minute intervals we measure how far it's gone up from the marked point. We do this for 10 minutes

For our second experiment we change the conditions of the plant, we place it next to a window so that the sun is shining directly on it to see if this will speed up the reaction

With the third, a black bag is placed over it, to see if the reaction will slow down.

Here is a diagram to show how this is set up.

Fair test

To make the test fair I will do the following things.

• Use a stopwatch to make sure the minute intervals are exact.
• I will make sure they are no other air bubbles in the tubing.
• I will make sure all the plants used have 24 leaves exact.
• I will leave all the plants to adjust for 10 minutes to their conditions.
• I will repeat each experiment 3 times each so that I can get an average.

I will then record the results in a table like this.

Prediction

I predict that experiment 1 will take in water normally as there are not certain conditions placed on the plant. Experiment 2 will take in water faster as it can photosynthesise more because of increase in sunlight. Experiment 3 will not take in as much water because there is no sunlight to photosynthesise with. These predictions are based on my scientific knowledge and the preliminary experiment.

Results of my experiment

Here are the results of my first experiment.

These are the results of my 2nd experiment.

These are the results of my 3rd experiment and this experiment went exactly as I predicted.

The next pages show these results in graph form.

Analysis of my experiment

Overall my experiment went well, although experiment 2 went wrong 1 and 2 were complete success in proving that different conditions do affect transpiration. Here are the specific observations of each experiment.

Experiment 1 (Graph 1)

I can't really analyse this plant was placed in normal conditions so I expected no strange results. There were no abnormal results for this experiment, however since experiment 1's results were significantly less I did wonder whether it was this experiment that went wrong and not 2. If possible I would have liked done this experiment again. This experiment again proves that plants take in water.

Experiment 2 (Graph 2)

As said before these results appeared to be incorrect, as the plant should have taken in more water although it still took in more water than 3, which does prove that sunlight is needed for transpiration to work, however something went wrong with this experiment as the water in take should have been higher than experiment 1. This is because of the increase in photosynthesis, thus the plants needs more water so more transpiration.

Experiment 3 (Graph 3)

As well as noticing the huge drop in the rate of transpiration, we also noticed when we took the bag off that they were water droplets on the leaf. This meant that while inside the bag, the water couldn't evaporate because the bag blocked out the heat as well. The water intake was much slower than both the experiment 1 and experiment 2. This was because the plant had no sunlight so not as much water was needed for photosynthesis.

Comparing (Graph 4)

This graph shows all of the averages of the experiments. As we can see, experiment 1 has a very high ending point compared to 2 and 3, this makes me suspect that might be the experiment that went wrong. 3 is in the right sort of place but 2 if 1 was done properly should be higher than 1.

Evaluation of my experiment

There were a few things wrong about my experiment however it still managed to prove my point of how different conditions affect transpiration, however experiment 2 still had strange results so I have thought up of a few reasons why experiment 2 had abnormal results.

• The plant was placed next to window; this might have somehow affected the plant's transpiration rate.
• The sunlight may not have been that bright on the particularly day.

Experiment 3 was also unable to evaporate any of its water from the top of the leaves since we found water droplets all over the leaves when we took the bag off.

How could I improve my experiment?

If I ever did this experiment again here are the ways in which I would improve my experiment

• I would use the same plant for every experiment.
• That the room temperature was about the same.
• Do the experiments at the same.
• For experiment 3, use a bag that would stay the same temperature as the classroom, the plant was unable to let water evaporate from its top leaves.
• For experiment 2 make sure the sun was quite bright.

All in all my experiment was generally a success obviously the experiments going wrong couldn't be helped but could have been easily done again and improved.