Grade 3 · Unit 1: Looking after plants

Plants need light and water

What happens to a plant kept in the dark?

These young plants have light, water, air and soil – everything they need.

What plants need

Plants need light, water, air and warmth to grow. They also need minerals from the soil. A healthy plant has strong stems and green leaves.

Plants do not eat food like we do. They make their own food in their leaves, but only when they have light.

Plants in the dark

A plant kept in the dark grows tall and thin. Its leaves turn pale yellow instead of green. It is weak and soon falls over. Without light, it cannot make food.

The pale plant is stretching to find light. If you put it back in the light, it can turn green again – if it is not too late.

Plants without water

A plant without water begins to wilt. Its leaves droop and dry. If it gets water soon, it can recover. If it has no water for a long time, it dies.

Different plants need different amounts of water. Rice grows in flooded paddy fields, but a cactus can live for months with almost no rain because it stores water in its thick stem.

Testing it fairly

Scientists use a fair test to find out what plants need. Take two plants that are the same. Change only one thing, such as light. Keep the water, soil, pot and temperature the same.

The thing you change is called a variable. If you changed two things at once, you would not know which one made the difference.

What I learnt