Is sunlight or water keeping this plant alive?

A plant on the windowsill stays green and happy. Move it somewhere else and it can droop, yellow, and die. So which one is really keeping it alive — the water you give it, or the sunlight it sits in? Let's grow one and find out.

1What a plant is really doing

A plant has to eat — but it builds its own food

You only need two ideas. Watch each one:

Every living thing needs food

Food is energy. You eat to get it. A plant needs energy too — to grow, to make leaves, just to stay alive. But a plant has no mouth and never swallows a thing.

A leaf is a tiny food factory

Light is the power switch. Flip it on and the leaf takes a gas from the air and water from the roots and builds its own sweet food. Flip it off and the factory makes nothing.

2Two very different things

The drink vs the build

It's easy to mix these up — but a drink and a meal are not the same thing:

Water from the roots

The drink

Water climbs up and keeps the plant plump so it doesn't wilt. But water is not food — it carries no energy.

Light + air + water

The build

With light, the leaf turns air and water into sugar — and that sugar is the food the plant lives on.

3Your turn — run the factory

Turn the light up and watch the leaf build sugar

Here's the inside of one leaf. Slide the light up and down. Watch the air and water flow in and little drops of sugar get built — fast in bright light, and stopping completely in the dark.

Sugar being built: fast 🍬
Slide the lightbright sun
PITCH DARKBRIGHT SUN

4Now the real test — the dark closet

Two watered plants. One in the dark. Run the days. 🌱

Both plants get the exact same water every day. The only difference: one sits in the sun, the other is shut in a pitch-dark closet. Guess what happens first — then run the days and watch.

Guess before you run the days

One plant sits in the sun, the other goes in a dark closet — but both get the exact same water every day. If you could pick just one thing to count on to keep a plant alive, which would you bet on?