This
weekend resulted in a trip to Grimley for a bit of birding. I really
love this time of year as there is a real possibility of anything
turning up. And with plenty of reports around the region of some
interesting birds I was very hopeful of finding a rarity or two.
However, I found very little. In fact from a birding point of view
the highlights were simply a few shovelers, a collection of wigeon, 7
little egrets and a couple of stonechats.
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| Grimley - Camp Lane Pits |
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| Stonechat |
Despite
this I still enjoyed my walk around the pits and along the river. The
colours were incredible and there is a real sense of being stuck
between two seasons. As the sun poked through the clouds I had a
glimpse of a few butteries and the odd dragonfly. I also spent lots
of time admiring the autumn colours. The full range of colours that
the leaves go is staggering. I know this was the main feature of my
last blog but the pure beauty of autumn is difficult to get over. As
a result I was easily inspired to do more on the topic.
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| Grmiley - Camp Lane Pits |
The
task was to carry out some chromatography on the different pigments
in the leaves. So I collected a range of different leaves and most
importantly different colours. To show the different stages of
Autumn. As we walked around the area we collected as much as we
could. We wanted to see as many of the different pigments that were
on show as possible. We were reminded of the compound interest
graphic showing what causes the green, yellow, orange and red
colours.
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| Compound Interests Chemistry of Autumn Colours |
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| Our Leaf Collection |
We
wanted to show that the yellow pigment is always present in leaves,
just not visible due the the abundance of chlorophyll. Chlorophyll is
the green pigment that absorbed sun light that the plant then uses to
carry out photosynthesis. It is green because it absorbs the red and
blue parts of the spectrum and reflects the green. We also wanted to
show that the red pigment develops later in autumn as a result of
chemical reactions in the leaves after the leaf has lost its
chlorophyll. The pigment is found in the cell sap and is formed when
proteins react with the sugars in the cell sap. The reaction requires
light and high concentrations of sugars.
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| Cutting and Crushing the leaves |
The
changing of the leaf colours is driven by a number of factors.
Firstly the low temperatures cause the plant to break down the
chlorophyll. Then the yellows are visible. The reds come from
further chemical reaction (hence not see in green leaf
chromatography). The leaf needs dry weather to help concentrate the
cell sap and then warm sunny days to accelerate the chemical reaction
between the sugar and cell sap. So if the conditions are right you
will get some stunning colours in the woodlands.
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| A bit of Careful Warming to Extract the Pigment |
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| Left Over Night |
When
we got home we couldn't wait to get started on the chromatography.
The first stage was to crush the leaves and soak them in a solvent.
We initially warmed the mixture before leaving it over night to
extract as much of the pigments as possible. Chromatography is a
separation technique. This means that we can separate out all the
different chemical found in the leaf. It uses to phases. First the
stationary phase – the paper – which holds onto the different
chemicals. The second stage is the mobile phase – the solvent –
which carries the chemicals trough the stationary phase. The result
is that in the green leaves you can see two colours: green and
yellow. In the yellow leaves you can only see yellow and in the red
leaves you can not see any green, just red and a little yellow.
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| The First Chromatogram - Both Green and Yellow Pigments |
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| Our Full Results |
The
results of this investigation confirm our hypothesis but more than
that it was a lot of fun. It was great to do some science as a family
and get some colourful results. In addition, we managed to connect
nature with scientific ideas.
