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Transcript of Leaf Chromatography
Results and Conclusion
Red leaves still contain chlorophyll like green leaves.
In green leaves, chlorophyll is the main photosynthetic pigment. The four main pigments are:
Chlorophyll A - blue-green
Chlorophyll B - olive green
Xanthophyll - yellow
Carotene - orange yellow
These other pigments may dominate when chlorophyll levels decrease.
Why do leaves change colours in the fall?
To determine if chlorophyll is still present in red leaves, chromatography can be used to recognise the four major pigments found in the different leaves.
Green and red leaf from the same specie tree.
Glass or plastic cups
Filter paper or chromatography paper
A coin to transfer the leaf pigments on paper
Cut filter paper into three, 1 inch strips. On the top of the strip with a pencil, mark the paper G for green leaf, R for red leaf.
Place the coloured leaf on the paper, 1 inch from the bottom and rub the coin on the leaf to transfer pigments onto the paper.
Pour alcohol into the cup just enough so that the alcohol touches the bottom of the papers but not enough where it is touching the rubbed pigment lines.
Place strips into the jar so the bottom of the strips are touching the alcohol. You may have to place a pencil on top of the cup so you can drape (fold over) the paper over the pencil so they don't fall in.
Watch the colours travel up the paper. Approximately 30 minutes.
Identify what colours are left on the filter paper from each coloured leaf.
It is clear that the green leaf contains all four pigments. ( chlorophyll a/b, xanthophyll and carotene)
The red leaf sample does not contain chlorophyll but instead shows signs of xanthophyll and carotene.
Results and Hypothesis
The results of the chromatography disproved my hypothesis that red leaves still contain chlorophyll.
As the days get shorter and cooler, it triggers a reaction from the trees that it is time to prepare for winter. During the winter, there is not enough sunlight for photosynthesis. The trees go dormant and live off the food that was stored from the summer. The green chlorophyll disappears as the leaves begin to shut down their food making factories.
As the greens fade away and the leaves turn to yellow, orange and red, these colours were in the leaves all along. We don't see them in the summer because chlorophyll is so dominant, it masks the other colours.
The colours we see in the fall such as bright reds and purples is glucose that is trapped in the leaves after photosynthesis stops. The shorter sunlit days and cooler temperatures causes the leaves to turn the glucose into a red colour. When the leaves turn brown and fall, there are dead plant cells and wastes that remain in the leaf.