WHY THE LEAVES CHANGE THEIR
COLOUR IN AUTUMN
SCIENTIFICS
MAITANE ARANBURU, NAHIA ARANGUREN, ONINTZE AZPITARTE and MARIA
BASETA.
ELORRIO BHI
INTRODUCCION:
We did this project because every year we see that the color of the leaves changes
in the autumn. A leaf is green because of the presence of a pigment known as
chlorophyll. The chlorophyll’s green color dominates and masks out the colors of
any other pigments that may be present in the leaf. Carotenoids are present in
leaves the whole year round, but their orange-yellow colors are usually masked by
green chlorophyll. As autumn approaches, certain influences both inside and outside
the plant cause the chlorophylls to be replaced at a slower rate than they are being
used up. During this period, with the total supply of chlorophylls gradually dwindling,
the "masking" effect slowly fades away. We wanted to know how long takes the
process under other controlled conditions and how will the change happen.
On other words, we wanted to reproduce under laboratory conditions what we see in
the nature and follow the whole process.
So we took three different boxes and we put them in three different places: One
under light conditions, near the window and close to the heating system to absorb
the sun and the heat that the sun gives.
The second box it was next to the heater but it was covered with a plastic layer to
prevent the passage of the light through it but leaving the plants breathing. The third
box it was in the darkest place of the laboratory with no light and no heater.
To carry on the experiment, we took four different trees and their leaves. But we had
some issues, because now in winter, the trees they haven’t got leaves, so we tried to
take the leaves that were available and tried to observe the change of the colour.
MATERIALS AND METHODS:
FOR THE VISUAL OBSERVATIONS:
- 3 different boxes.
- 4 types of different leaves, 12 in total
- Water
- Recipients to put the leaves on it.
- Plastic to cover one box
FOR CHROMATOGRAPHY :
-
Materials
Soft green leaves
Scissors
Mortar and pestle or food processor
Glass or ceramic cup
Isopropyl alcohol (or acetone in nail polish remover, but be
careful—acetone creates more fumes)
Flat coffee filters
Tape
Pencil or straw
METHODS:
Organization of the boxes:
We distribute the same types of leaves in tree boxes. We have taken into account
the temperature of the laboratory and also the light that was there.
● First box: this box was open and like this, the natural light enters there. We
put it next to the window and like this the light entrance is allowed there.
● Second box: to the second box received also the natural light but light was
restricted by using a layer of plastic film. We did some holes to the plastic
and like this, the leaves could breathe.
● Third box: the third box was isolated from light, it was covered with a
cardboard. Doing this, we prevent the entry of light in the box.
Visual observations
Chromatography:
We did a chromatography to see that in leaves there are more pigments apart from
the chlorophyll (which is the most abundant pigment in leaves), and different colours
appear as time goes on (most of their brown). We see too that as time passes the
green and yellow colour was disappear and the brown colour pigment remains there.
Procedure of the chromatography:
1. Use the scissors to cut up enough leaves to make a ¼ cup of pieces.
2. Use the food processor or mortar and pestle to grind the leaves into a fine pulp.
3. Pour the pulpy leaves into the cup.
4. Pour enough isopropyl alcohol over
the leaves to cover them. Stir.
5. Cut out strip of coffee filter paper
about 6 inches long and 1 inch wide.
6. Attach the strip to the pencil with a
piece of tape. Make sure the bottom
of the strip hangs straight.
7. Adjust the length of the filter paper
strip so that the bottom just touches
the green liquid in the cup.
8. Checking every couple minutes,
wait for the band of solvent to migrate
to the top of the filter paper. Different
colored bands should become evident
along the strip.
9. Study your strip, and try to identify
the pigments.
Results of the chromatography:
The results will vary depending on the types of leaves that you chose and how
careful your leaf chromatography technique was. You might not see all the pigments.
An orange-colored band is likely to be near the top.
Below that, you should see a yellowish band, a blue-green band, and a greenishyellowish band, respectively.
EXPERIMENTS:
Taking into account the temperature:
In the box that we put near the light, we measured also the temperature. We put the
first box next to the window to obtain the most solar influence. The second box which
was covered with a plastic film…..
The third one was covered with a cardboard, we put it in the coldest place of the
laboratory.
We measured the Temperature each day:
FEBRUARY
OBSERVATION OF THE COLOUR OF THE LEAVES
BOX 1
LEAF 1
LEAF 2
LEAF 3
LEAF 4
24/02/2016
18ºC
Green
Green
Green
Green
25/02/2016
18ºC
Green
Green
Green
Green
26/02/2016
19ºC
No
significant
changes
No
significant
changes
No
significant
changes
No
significant
changes
29/02/2016
Starts
changing
to brown
16ºC
No
significant
changes
No
significant
changes
Starts
losing the
green
colour
FEBRUARY
OBSERVATION OF THE COLOUR OF THE LEAVES
BOX 3
LEAF 1
LEAF 2
LEAF 3
LEAF 4
24/02/2016
18ºC
Green
Green
Green
Green
25/02/2016
18ºC
Green
Green
Green
Green
26/02/2016
19ºC
No
significant
changes
No
significant
changes
No
significant
changes
No
significant
changes
29/02/2016
16ºC
Starts
changing
to brown
No
significant
changes
No
significant
changes
Starts
losing the
green
colour
MARCH
OBSERVATION OF THE COLOUR OF THE LEAVES, BOX 1
LEAF 1
LEAF 2
LEAF 3
LEAF 4
01/03/2016
17ºC
No
significant
changes
No
significant
changes
No
significant
changes
No
significant
changes
02/03/2016
17’5ºC
The back of
the leaves
get brown
No
significant
changes
No
significant
changes
No
significant
changes
03/03/2016
17ºC
No
significant
changes
No
significant
changes
No
significant
changes
Stars losing
the green
colour
04/03/2016
17ºC
Changing to No
the brown
significant
colour
changes
No
significant
changes
No
significant
changes
07/03/2016
16’5ºC
No
significant
changes
No
significant
changes
No
significant
changes
No
significant
changes
11/03/2016
17ºC
Start
spoiling
No
significant
changes
No
significant
changes
No
significant
changes
14/03/2016
16ºC
Spoil
Star lighten
No
significant
changes
Start
lighten
MARCH
OBSERVATION OF THE COLOUR OF THE LEAVES, BOX 3
LEAF 1
LEAF 2
LEAF 3
LEAF 4
01/03/2016
17ºC
No significant
changes
No significant
changes
No significant
changes
No significant
changes
02/03/2016
17’5ºC
The back of
the leaves
get brown
No
significant
changes
No
significant
changes
No
significant
changes
03/03/2016
17ºC
No
significant
changes
No
significant
changes
No
significant
changes
Stars losing
the green
colour
04/03/2016
17ºC
Changing to No
the brown
significant
colour
changes
No
significant
changes
No
significant
changes
07/03/2016
16’5ºC
No
significant
changes
No
significant
changes
No
significant
changes
No
significant
changes
11/03/2016
17ºC
Start
spoiling
No
significant
changes
No
significant
changes
No
significant
changes
14/03/2016
16ºC
Spoil
Star lighten
No
significant
changes
Start
lighten
We didn’t open the 2 box because if the solar light enters into the box, the intensity
of the light was going to change .
We put in a paper different colors and all the days we compare if the color changed.
But it doesn’t changed.
RESULTS:
We had planned to have two types of results in this experimental work: on one hand,
the results obtained from our visual observations and on the other hand, the results
of the paper chromatography, but we realized that in one part of the project we had
some measurable results, but in the other we hadn’t.
As we explain in the methods, one part consisted on the visual observations during
the box phase and the other consisted on the chromatography method.
In this second phase we obtained some quantifiable results.
We verify that in the tracking that we do to the leaves, only writing down which we
see, with any touching, doesn't change anything. It doesn't change color, only it rot.
This in the three different box that we have.
Results of the chromatographies:
● The chromatography of the leave “1”:
As we can see the first and the second chromatography they
have more green colour than the last. This means that the first
and second leaves have more chlorophyll b than the last one,
and the last has more xanthophyll than the others.
❖ The first image is the day 1, the second day 8 and the
third day 16.
● The chromatography of the leave “2”:
In this case we can appreciate the chlorophyll b and the
xanthophyll in the first and last chromatography. In the
second we observe few substances. Only a little bit of
chlorophyll b.
❖ The first image is the day 1, the second day 8 and
the third day 16.
● The chromatography of the leave “3”:
Here also we see that the results are the same as the other
leaves. The first leave hasn´t got many substance, only
chlorophyll b. The others leaves, apart from chlorophyll b, have
xanthophyll too.
❖ The first image is the day 1, the second day 8 and the third
day 16.
● The chromatography of the leaves “4”:
In this first chromatography we can observe clearly that has
chlorophyll b and xanthophyll. In the other two, also, we can
appreciate chlorophyll b and xanthophyll.
❖ The first image is the day 1, the second day 8 and the third
day 16.
Results of the chromatography:
Your results will vary depending on the types of leaves that you chose and
how careful your leaf chromatography technique was. You might not see
all the pigments. An orange-colored band is likely to be near the top.
Below that, you should see a yellowish band, a blue-green band, and a
greenish-yellowish band, respectively.
CONCLUSIONS:
The conclusion that we can obtain taking into account the results is , that the color of
the leaves varies in different periods of time.
IN THE VISUAL OBSERVATION:
We saw that the color of the leaves doesn´t change, so in the visual observation we
hadn´t have any positive result.
IN THE CHROMATOGRAPHY:
When you ground up your leaves, the pulp was probably green because of the
overwhelming amount of chlorophyll. You were instructed not to use water as a
solvent because the pigments in leaves are not very soluble in it: they are much
more soluble in solvents like alcohol or nail polish remover. The orange colored
band, made of the pigment called carotenoids. is the most soluble in alcohol, so it
traveled the farthest. The yellow xanthophylls are the next most soluble, followed by
the blue-green chlorophyll A. The least soluble pigment is the yellow green
chlorophyll B. You may be wondering why plants have more than one pigment. One
reason is that these differently colored pigments absorb different colors of light: by
having many pigments, plants can use more of the light energy shining down them.
BIBLIOGRAPHY:
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http://www.sciencemadesimple.com/leaves.html
http://www.esf.edu/pubprog/brochure/leaves/leaves.htm
Leaf Chromatography
http://www.education.com/science/fair/article/find-color-pigments-hiddengreen/