By Ms. Du Plessis.

Have you ever wondered why leaves change their colour and fall off during Autumn?
Like in people’s skins, the colour comes from pigments. Leaf colour also comes from
pigments, which are natural things (substances) produced by leaf cells to help them get
food. The three pigments that colour leaves are chlorophyll (green), carotenes (yellow) and
anthocyanins (reds and pinks).
The weather conditions and chemical processes will influence the colour of leaves .
– Cold nights: low temperatures destroy chlorophyll so the green leaf fades to yellow.
However, if temperatures stay above freezing, anthocyanin production is higher and
the leaves take on a red colour.
– Dry weather: sugars become concentrated in the leaves, more anthocyanin is
produced and then leaves are redder.
– Bright sunny days: although new chlorophyll production stops in autumn,
photosynthesis still occur on sunny autumn days by using the remaining chlorophyll.
Sugar concentration then increases and more anthocyanin is produced – which gives
leaves a deeper red colour.

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But why do trees lose their leaves?

Abscission, also known as the beginnings of leaf drop, start when a layer of cells is formed
where the leaf stalk joins the stem. This layer, known as the abscission layer, is formed in
the spring during active new growth of the leaf.
In autumn, hormones within trees begin to change. Yes – trees also have hormones! The
hormone responsible for the growth of leave stems is called auxin. During the growing
season, the production of auxin in the leaves are the same with the rest of the tree. As long
as these rates are steady, the cells of the abscission layer remain connected. This keeps
leaves attached.
But as days shorten and temperatures cool down, the auxin production in leaves decrease.
This results in cells getting longer in the abscission layer – where the leave stalk joins the
stem. When this happens, leaves start to break away from the plant, and is finally blown off
by the wind, or falls from its own weight.

Information from http://www.woodland.org.uk

Now that we all know a bit more about how the beautiful autumn leave colours are created and why they drop down from the trees, let us be thankful for they joy they bring. And also for knowing that in Spring, new life will start again!

Ms. Lola.