When you look at a tree, you only see a part of it. Unseen roots spread out underground as wide as the branches above. These roots anchor a tree in the ground and hold it up against the force of the wind. Roots also help the tree to grow, by taking up water and nutrients from the soil through the trunk to the leaves. Trees act like a natural pump – many trees over 165 feet tall pump hundreds of gallons of water a day in order to grow. You can suck a drink up through a straw, but trees cannot do this. They use a method called osmosis to draw the water upward. The first experiment shows how osmosis works. Water inside the roots (sap) has a higher concentration of sugar than the water outside. The process of osmosis draws water from the soil, where the concentration is low, to inside the root, where concentration is high.
The second experiment uses colored water to show how water actually travels up a plant’s root. All living things are made up of little units called cells. Water can travel through cell walls but sugars cannot. During osmosis, water always moves in a set direction – from the side where there is less sugar dissolved in it to the side where there is more.
Large potato, ruler, chopping board, peeler, knife, teaspoon, two shallow dishes, water, sugar.
Water, two tall drinking glasses, water-soluble ink or food dye, white carnation, scissors, tape.
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