Science 8th grade
UNIT 1: Plants 1.4 Roots
Science 8th grade
UNIT 1: Plants 1.4 Roots
Roots are usually underground, so we often do not notice them. But, for many plants, the roots take up just as much space as the above-ground parts of the plant.
Functions of roots
The roots of a plant have several functions.
• Roots absorb water and minerals from the soil. These are then transported to all the other parts of the plant.
• Roots anchor the plant firmly in the ground, so it is not pulled out when the wind blows strongly, or when ananimal pulls on the leaves.
• Some plants store food in their roots.
• When conditions are difficult-for example, in a cold winter, or a dry summer - some plants allow their aboveground parts to die. Only the underground roots continue to live. New shoots (above-ground parts) grow from the roots when conditions become better.
Activity 1.4A (Roots for food)
We make use of many roots that store food. The plant stores the food for its own use, but we can also eat this food.
Choose two different roots that humans eat as food.
For each root, find out what the complete plant looks like.
Make a labelled drawing of the plant. Describe how we use the root for food.
How roots absorb water and minerals
Soil is made up of tiny rock particles. There is usually water in the spaces between the particles. There are minerals dissolved in the water.
You may remember that special cells called root hairs grow out of the surface of roots. Root hair cells provide a really big surface through which water and minerals can be absorbed.
Questions
$A + I$: 1) Explain how the absorption of water by roots helps photosynthesis to take place.
$A + I$: 2) Suggest why most plants die very quickly if their roots are cut off.
3) Explain how root hairs help plants to absorb a lot of water in a short time.
Activity 1.4B (Which way up?)
SE: 1) Take a tall glass jar. Roll up a piece of strong absorbent paper so that it fits inside the jar. Add a little water and allow it to soak into the paper.
2) Take three soaked bean seeds. Carefully put them between the paper and the side of the jar. Place each one a different way up.
3) Put the jar in a warm place. Check it cach day to see if it needs more water - it is important to keep the seeds moist but not too wet.
4) When all of the seeds have grown roots, make drawings of them.
Questions
${A_1}$: What do you notice about the directions the roots have grown in?
${A_2}$: Suggest how this would help a bean plant to survive.