Water Transport in Plants
Investigate how water is transported within plants, using observations such as coloured water being drawn up through a stem
What a learner can do afterwards
- Describe an investigation using coloured water to track water movement in a plant
- Explain that water travels from roots through the stem to the leaves and flowers
- Draw or label a diagram showing the path of water through a plant
1 · Read
Roots absorb water from soil. Thin tubes called xylem carry water through the stem to leaves and flowers. Leaves and flowers are separate destinations; water need not pass through a leaf to reach a flower. Much of the water later leaves the plant as water vapour through tiny openings in its leaves.
Ask an adult to prepare a fresh white flower's cut stem. Stand its cut end in water mixed with food colouring. White petals make added colour easier to notice than dark petals. After several hours or the next day, coloured patches may appear. Dye travels with water through the stem. This flower has no roots attached: water enters at its cut stem.
To draw the soil-water route, label the roots, stem, leaves and flowers. Draw arrows from roots into the stem, then from the stem towards leaves and flowers. For a cut flower in a cup, start the arrows at the cut end of the stem in the water.
Compare matching fresh white flowers in equal amounts of water. Add red food colouring to just one cup. Leave both for the same time. Both flowers can take in water, but only the dyed water can leave red patches. White petals in clear water do not mean that no water moved.
Record the petal colour before the test and check again later. A visible change can take hours or longer. White petals after five minutes do not show that stems cannot carry water. Wait and record what you actually see. Do not drink the test water or eat the test plants.
Water starts at the roots, travels up the stem, and reaches the leaves and flowers.
Readings independently written for this dataset, with flashcards reviewed for the same topic. Background facts include roots and water transport described in OpenStax Biology.
More to read
Following water through a flower stem
A flower growing on a plant can receive water that the roots absorbed from soil. The water passes through tubes in the stem. These water-carrying tubes are called xylem.
A cut flower has no roots attached. Its cut stem can take in water from a cup instead. Mixing food colouring into the water gives us a marker. Coloured patches on white petals show that dye has reached those parts of the flower with the water.
Ask an adult to prepare a fresh white flower's stem. Note its petal colour before the test. Check again after several hours and the next day. Record what you see, even if there is no visible change yet.
White petals make added dye easier to notice than dark petals. The whole flower need not change to one solid colour. Do not drink the test water or eat the test plant.
Water entering and leaving a plant
Roots help hold many plants in soil and absorb water and minerals. Some roots also store food made by the plant. A carrot's thick root is one example. Roots are not always underground; some plants have roots above the ground too.
Tiny root hairs give a root more surface for taking in water. Water entering a root can pass into the water-carrying tubes and move through the stem towards leaves and flowers. Leaves and flowers are different destinations, not two stops that all water visits in order.
Much of this water later becomes water vapour and leaves through tiny openings in leaves. This water loss helps pull more water through the plant.
For a drawing of water taken in from soil, start the arrows at the roots. Continue through the stem, then towards leaves and flowers. For a cut flower standing in a cup, start at the cut stem instead.
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