The roots of a tree are usually under the ground. One case for which this is not true are the roots of the mangrove tree which are often under water.
The leaves of a tree are green most of the time, but they can come in many colours, shapes and sizes. The leaves take in sunlight and use water and food from the roots to make the tree grow, and to reproduce.
This is the opposite of what animals do in respiration.
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From @arifulislamlimon