There are many kinds of trees. All trees have roots. The roots hold trees in the ground. The roots soak up ( 吸收 ) water and food. Then trees get water and food from the roots. You can't see inside a tree. But you can study how water moves through trees.
First, get a stalk ( 茎 ) of celery ( 芹菜 ) and cut off its end. Put red colour in a cup of water. Then put the stalk of the celery into the red water. Then we can see the red water moving up in the celery easily.
After half an hour, take the celery out. Cut it in half. Your celery should be red. This is because the water moved up the stalk. Water moves through trees in the same way as it moved through the celery.
