We don’t think much about them – the green blur of the forest which forms the backdrop of our daily lives. But every tree contains thousands of leaves and each leaf tells a story of wonder – a story worth sharing with our children.
The sheen of green you see in a leaf is created by special cells that contain chlorophyll (green in colour) – these are the food-making cells for the tree. And really their presence is nothing short of a miracle. It has an unwieldly name of “photosynthesis”. “Photo” is the Greek word for “light” and “synthesis” is the Greek word for “putting together.” And that is exactly what is happening. Here is one way to explain the magic of leaves and the process of photosynthesis to children:
Sun: The “Light Snack”
Grab a handful of sunlight. Now don’t let this slip through your fingers. Cram this into your mouth – chew and swallow. Now that is what you call a “light” lunch. OK, people can’t really eat sunlight – at least not directly. But trees can. And so can other plants. Inside each leaf are little factories (chloroplasts) that take the sun’s energy, carbon dioxide and water to make sugar. Every single leaf is like a mini solar panel, making food straight from sunlight. A by-product plants don’t need is oxygen. Now let’s take a moment to stop and think about this. Breathe in. The oxygen you are taking into your lungs was made by plants. Breathe out, the carbon dioxide you don’t need is taken up by plants. What a cool arrangement! Trees uptake carbon and give off oxygen. You take in oxygen and give off carbon dioxide. Without trees and plants – there would be no way to capture the sun’s energy and make it available to animals like you and me. Plants and trees are the miracle workers that turn solar energy into people energy. Trees also make the surrounding air more moist; their roots help the soil to retain water and they provide critical habitat for many birds, insects and animals.
Why are leaves green? Leaves contain an amazing chemical called chlorophyll. It is green in color and made out of rare and precious minerals or nutrients such as magnesium from the soil.
Why have trees evolved so tall? So they can reach for the sunlight. They don’t want to be shaded out by their neighbour or die from lack of sunlight.
Why are some leaves bitter or poisonous? They prevent insects like caterpillars, birds and mammals from eating them.
Why are there so many different sizes and forms of leaves? When you have lots of little leaves on one stem (compound leaves), this arrangement allows air to circulate, cooling them. Large leaves gather more light and are, therefore, necessary in shady areas and on the lower, more shaded branches of trees, for example, hosta.) Complex edges and lobes allow leaves to get rid of absorbed heat very rapidly; smooth edges are more common in shade-loving plants because getting rid of heat is not as much of a problem.)
Why do some trees turn colour in the fall? The uniform green of the forest, which is the hallmark of any summer’s day, slowly transforms into majestic hues of yellow, gold, mauve and crimson. The funny thing is that many of those fall colours have been there all along. Their green colour covers up other pigments like yellow and orange (carotenes and xanthophyll pigments) that are hidden from view until the days shorten and the temperature drops. During the cooler days of autumn, chlorophyll breaks down and the other pigments pop out and show themselves. There are other pigments forming during this time, such as anthocyanin which gives leaves their vibrant red and purple colours.
Submitted By Jacob Rodenburg, Executive Director of Camp Kawartha, an award winning outdoor education centre and summer camp.