What plants need to grow well

Four things a plant needs

Light, water, air and warmth — plus space and nutrients from the soil. Take away any one of them and the plant grows badly or dies. Notice that plants do not need to be given food: they make their own, which is the biggest difference between plants and animals.

What happens when one is missing

Without light, leaves turn pale yellow and the stem grows long and weak as it stretches towards any light there is. Without water, the plant wilts and droops. These two pictures are worth remembering because Checkpoint shows them and asks what was missing.

Testing a plant need

To test whether light matters, grow two identical plants and change only the light. Everything else — same pot, same soil, same water, same warmth — must stay the same, or the result proves nothing.