What Plants Need

Define and explain What Plants Need in your own words
Use key terms such as photosynthesis accurately
Apply what you have learned to new examples and questions
Avoid the common mistakes learners make with this topic

This lesson focuses on What Plants Need: discover the light, water, warmth and air that plants need to stay healthy and grow.

Definition: What Plants Need

Discover the light, water, warmth and air that plants need to stay healthy and grow.

Key ideas

Plants need light, water, warmth and air to grow well. Without enough light, stems grow tall, pale and weak as they stretch towards it. Without enough water, leaves droop and wilt. Gardeners test one need at a time, keeping everything else the same, so they know exactly what makes the difference.

The jobs of plant parts

Roots anchor the plant and take in water and minerals. The stem holds the plant upright and carries water up to the leaves. Leaves are the food factories where photosynthesis happens. Flowers make seeds so new plants can grow. Each part has a job, and the plant suffers if any part is damaged.

Key term — photosynthesis: The process by which green plants use light energy to make food (glucose) from carbon dioxide and water.

Worked example: What Plants Need

List three things a plant needs to grow healthily.

Any three of: light, water, warmth, air (carbon dioxide).

Answer: Any three of: light, water, warmth, air (carbon dioxide).

Common mistakes

Saying plants eat soil Plants absorb water and minerals from soil, but they make their own food in their leaves using sunlight. Soil is not their food.
Forgetting that roots grow first During germination the root appears before the shoot, so the young plant can absorb water straight away.

Practice

In the fair test example, why must both plants get the same amount of water?

What would happen if only one got water?

So that water cannot explain any difference in growth. If only one plant were watered, you would not know whether light or water caused the result.

What happens during germination?

What comes out of the seed first?

The seed starts to grow: the root emerges first to absorb water, then the shoot grows upwards towards the light.

What is the job of the roots?

Think about water and holding on.

Roots anchor the plant in the soil and absorb water and minerals.

Why are green plants called producers?

What do they make that animals cannot?

Because they produce their own food by photosynthesis, so they are the starting point of food chains.

Quick check

What Plants Need — quick check

Which of these best defines "photosynthesis"?

The process by which green plants use light energy to make food (glucose) from carbon dioxide and water.

Name the four main parts of a flowering plant.

Roots, stem, leaves and flower.

Key takeaways

What Plants Need: discover the light, water, warmth and air that plants need to stay healthy and grow.
What plants need: Plants need light, water, warmth and air to grow well.
roots: The part of the plant that grows underground, anchoring the plant and absorbing water and minerals from the soil.
Watch out for: saying plants eat soil

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