Week 5

 Autumn Leaves

October really is a beautiful month; the landscape is alive with glowing, jewel tones; but where do those wonderful colours come from?

Inside each leaf are various pigments; the green is chlorophyll, the yellow is xanthophyll, and the orange, carotene. During spring and summer, the chlorophyll is working very hard, catching sunlight to use as energy, and converting the carbon dioxide in the air and the water from the ground into glucose, (sugar) which is food for the tree.

Because the chlorophyll is working so hard, the green pigment covers up the other pigments present in the leaves. As autumn approaches, the weather gets colder and the days shorter. This signals the tree to prepare for winter. Instead of the tree continuing to absorb water into the leaves, cell membranes grow over the tubes that the water travels through. Without this water present, the green chlorophyll begins to diminish and the other pigments present in the leaves, the yellow xanthophyll and orange carotene, are finally visible.

The leaves have always been these glorious colours! But it is only when the chlorophyl pigments are gone can we see these wonderful shades.

Autumn leaves can also be shades of red, or even purple. When the tubes within the leaves close off to prevent more water getting in, sometimes sugars are trapped within those tubes. The sugars can cause the sap to turn red or purple, which appears as beautiful colours in the leaves.

Once the leaves no longer have water and food inside them, they begin to die. The green chlorophyll dies off first, then the yellow xanthophyll and orange carotene. When all the pigment is gone, the leaves are brown and usually crunchy.

Autumn Leaves

Autumn Foliage By Tom Thomson (1877-1917)

Oil on wood. Canada. 1915

A poem to enjoy this week:

October's Party by George Cooper

October gave a party;

The leaves by hundreds came—

The Chestnuts, Oaks, and Maples,

And leaves of every name.

The Sunshine spread a carpet,

And everything was grand,

Miss Weather led the dancing,

Professor Wind the band.

The Chestnuts came in yellow,

The Oaks in crimson dressed;

The lovely Misses Maple

In scarlet looked their best;

All balanced to their partners,

And gaily fluttered by;

The sight was like a rainbow

New fallen from the sky.

Then, in the rustic hollow,

At hide-and-seek they played,

The party closed at sundown,

And everybody stayed.

Professor Wind played louder;

They flew along the ground;

And then the party ended

In jolly "hands around."