Leaves
Leaves come in all shapes and sizes, but they are mostly always flat, green, and do not cover each other on a tree branch. Why? Well, being flat and well-spaced allows more sunlight to reach the leaf – and sunlight, together with that green stuff (known as chlorophyll) inside the leaf, need to mix together in a very important process known as photosynthesis.
But two other things are needed for the process to work: water and carbon dioxide. The water comes from the ground, and the carbon dioxide from the air. With all these products inside the leaf, the sunlight is changed into energy for the tree. This energy is stored by making a sugar – glucose – and other organic products – for example, more leaves, fruits, and vegetables. This is what we eat. And we eat animals which eat the leaves – meaning that leaves are the basis of the ‘food chain’. In other words, trees, plants, and bushes create all of the organic materials which are needed for life on Earth.
Another very nice result of photosynthesis is that oxygen, which we all breathe, is released. This is, obviously, very important, since photosynthesis keeps up the oxygen levels in the world. And because there are so many leaves, it adds up to a lot of oxygen, and a lot of sunlight changed into energy. If all the energy created by leaves were measured, it would be over three times the power used by people on this earth. Wow, leaves are important, right?
One final thing: in the autumn, many trees decide to shed their leaves as a defence against the oncoming winter. In the process of dropping these leaves, they slowly change colour from green to red/yellow/grey/brown, resulting in beautiful autumn scenes, such as the one in the picture above.
Question Time
Why are leaves usually flat? ……………………………………………………………
What is the green stuff inside leaves called? ………………………………….……..
What is the name of the sugar which leaves make? ……………………….……….
What else do leaves make which is important? …………………………….……….
How much energy do leaves make? …………………………………………………
Word-Learning Time
Do you know the meaning of the underlined words?
Flat
Branch
Carbon dioxide
Organic
Oxygen
Released
To shed
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